Low water pressure/flow in house

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Pete12
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Low water pressure/flow in house

Post by Pete12 » Tue Oct 29, 2019 1:11 pm

We are in the process of moving house but there is a problem with the water pressure / flow in the new property. We just had the engineers inspection completed and I am trying to get an education to see what may be involved before reaching out to plumbers, and also to see if we should ask for a credit from the seller.

It is a single family home, 2 floors, on city water. The city supply is soft water. It appears the house is supplied by a 1 inch copper pipe from the street. The water meter and main shut off are located in the basement. The house was built in the 1920s but was recently renovated and it appears all the interior plumbing is copper. There are no water softeners or whole house filters installed. There is no pressure relief valve on the incoming supply. We confirmed all shut off valves are fully open.

There is a hose bib right after the water meter. We attached a pressure gauge to it and the pressure reads 60 psi with no faucets on.

The problem is mainly on the second floor where there are three bathrooms. Running one of the showers at a time produces flow that is acceptable but not great. The flow reduces when two showers are running. Then running the third shower results in the flow going down to a trickle.

Looking at the pressure gauge, when the three showers are running the pressure drops to 20 psi.

The engineer suggested that a water booster pump with a tank would resolve the issue. Something like this: https://www.amtrol.com/product/city-pressure-boosters/

This sounds fine and can easily be installed by a plumber but are there are any other issues I should be considering? The engineer would not speculate on any causes of the low pressure. I am mainly concerned about whether there may be a problem with the supply line coming from the street, which would be an expensive proposition to replace, not to mention the resulting damage to the landscaping and sidewalk.

Hoping the Bogleheads can point me in the right direction here, happy to provide any other information. Thanks in advance!

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Re: Low water pressure/flow in house

Post by barnaclebob » Tue Oct 29, 2019 1:21 pm

Are you sure that all upstairs showers aren't being supplied by one 1/2" pipe or something? I've got extremely high water pressure (maybe too high and I need to look into it) but as soon as you try to do two things at once in my house the water flow rate drops because my whole house is pretty much fed by a single 1/2" pipe.

That single skinny pipe splits 3 ways shortly after the main shutoff so I can probably put a 1" pipe up to that split and it will greatly improve the situation, just haven't gotten around to it yet.

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Re: Low water pressure/flow in house

Post by RickBoglehead » Tue Oct 29, 2019 1:29 pm

Running three showers at the same time is not going to work almost anywhere.

Have you removed all showerheads and measured the flow coming out of the straight pipe into a bucket? Turn it on full cold and time how much goes into the bucket in 15 seconds and extrapolate out for gallons per minute. Repeat on every shower, every sink, and then do it downstairs too. If they all seem fine, it's time to check aerators / filters on each device. Could just be a clogged filter.

Or, as was suggested, perhaps the upstairs plumbing is run off one pipe? If so, that should be 3/4" that then drops to 1/2" at each sink/shower, etc. If they feed the whole upstairs with 1/2", that could be an issue.
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Re: Low water pressure/flow in house

Post by Smoke » Tue Oct 29, 2019 1:35 pm

barnaclebob wrote:
Tue Oct 29, 2019 1:21 pm
Are you sure that all upstairs showers aren't being supplied by one 1/2" pipe or something? I've got extremely high water pressure (maybe too high and I need to look into it) but as soon as you try to do two things at once in my house the water flow rate drops because my whole house is pretty much fed by a single 1/2" pipe.

That single skinny pipe splits 3 ways shortly after the main shutoff so I can probably put a 1" pipe up to that split and it will greatly improve the situation, just haven't gotten around to it yet.
+1

one inch main from the street does little good if the house is plumbed in 1/2" after it enters the home, and then that 1/2" splits to the rest of the house.
60 psi is good.
If the plumbing is accessible in the basement it may be possible to trunk off of the 1" main to different bathrooms, kitchen etc. with each "room" having it's own tap from the 1" main.
The water heater would have to have it's own tap 1" or 3/4", and then separate outgoing taps from the water heater to each room.
More than likely you will not be able to do each room separately, but separating some is better than none.
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Re: Low water pressure/flow in house

Post by BuddyJet » Tue Oct 29, 2019 1:37 pm

Before going further, I'd go to one of your potential new neighbors, explain the issue, see if they have a similar upstairs pressure drop and ask if you can check the pressure at one of their outside bibs. From that, you will have evidence to point towards your house in particular or the neighborhood in general.

Like others, it sounds like a supply pipe restriction. Be careful boosting the pressure too much or leaks might be an issue.
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Re: Low water pressure/flow in house

Post by Smoke » Tue Oct 29, 2019 1:46 pm

RickBoglehead wrote:
Tue Oct 29, 2019 1:29 pm
Running three showers at the same time is not going to work almost anywhere.
+1
Arguing for the sake of arguing is something I am not going to engage in.

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Re: Low water pressure/flow in house

Post by researcher » Tue Oct 29, 2019 1:49 pm

Pete12 wrote:
Tue Oct 29, 2019 1:11 pm
The problem is mainly on the second floor where there are three bathrooms. Running one of the showers at a time produces flow that is acceptable but not great. The flow reduces when two showers are running. Then running the third shower results in the flow going down to a trickle.
Do you have a need for three people to be taking showers simultaneously?
Does your home even have the capacity to supply that much heated water?
3 showers running at the same time, all on the second floor, is a tall order for any normal house and water supply.

You should remove one of the shower heads and install the pressure gauge there to see what you are working with upstairs.

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Re: Low water pressure/flow in house

Post by Grt2bOutdoors » Tue Oct 29, 2019 2:00 pm

Smoke wrote:
Tue Oct 29, 2019 1:46 pm
RickBoglehead wrote:
Tue Oct 29, 2019 1:29 pm
Running three showers at the same time is not going to work almost anywhere.
+1
+1. Asking the sellers for a credit, they are going to get a good chuckle out of it but you aren't getting any money for that. That is a behavioral issue, who takes three showers simultaneously? A 60psi flow from the street is great, a higher psi would likely cause a pipe somewhere in your home to break.
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Re: Low water pressure/flow in house

Post by brianH » Tue Oct 29, 2019 2:00 pm

RickBoglehead wrote:
Tue Oct 29, 2019 1:29 pm
Running three showers at the same time is not going to work almost anywhere.
You can look at charts like this: http://s3.supplyhouse.com/product_categ ... -Chart.pdf to see that even in an ideal situation, if your upstairs main line is 3/4 copper, that only gives 3.2-6.5gpm. Modern shower heads are restricted to max of 2.5gpm, but older heads or ones without the restriction device installed (*) can be more like 3-4gpm. Obviously, 3 showers at 2.5gpm is not able to flow full with 3/4 copper.

(*) I laughed at one shower head that I installed that had a section in the manual showing where the restriction device was, the fact that it was bright red, and that it could easily be removed for 'cleaning'. The manual, of course, did not recommend that you do so, as it would run afoul of Fed/local laws.

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Re: Low water pressure/flow in house

Post by Pete12 » Tue Oct 29, 2019 2:03 pm

Thanks everyone. Unfortunately we don’t know the size and configuration of the pipes feeding the showers. As we don’t own the property yet we aren’t in a position to start opening up walls LOL

My main concern at the moment is why the pressure at the meter drops off so much from 60psi with nothing running to 20psi with the three showers on. Any thoughts on this?

Agree that in practice there probably won’t be three showers going at exactly the same time...

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Re: Low water pressure/flow in house

Post by 123 » Tue Oct 29, 2019 2:05 pm

Are you in an area where everyone expects the water to gush out from the shower like a fire hose?

We live in California where we are required to be more miserly with our water. We've got a 50 gallon hot water heater and we can have 3 showers running simultaneously but each has a 1.5 gpm showerhead. People that like a fire hose shower would call that a mist but it works quite well.
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Re: Low water pressure/flow in house

Post by neilpilot » Tue Oct 29, 2019 3:14 pm

Pete12 wrote:
Tue Oct 29, 2019 2:03 pm

My main concern at the moment is why the pressure at the meter drops off so much from 60psi with nothing running to 20psi with the three showers on. Any thoughts on this?
Likely not a concern....that pressure drop sounds normal. The average US shower flow is 2.1 gpm. At 6 gpm the minimum pressure drop thru a 1/2" pipe is almost exactly 40 psi. I'd guess the header(s) feeding your showers is likely 1/2".

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Re: Low water pressure/flow in house

Post by billc23 » Tue Oct 29, 2019 3:27 pm

It may be a problem with the one inch copper into the house. Are you able to run a faucet near the meter and check the pressure?
The pressure drop occurs along the length of 1/2 inch pipe but should not drop too much at the meter coming into the house.
There may be some galvanized pipe between the street and the house causing the drop.

Bill

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Re: Low water pressure/flow in house

Post by Pete12 » Tue Oct 29, 2019 3:49 pm

billc23 wrote:
Tue Oct 29, 2019 3:27 pm
It may be a problem with the one inch copper into the house. Are you able to run a faucet near the meter and check the pressure?
The pressure drop occurs along the length of 1/2 inch pipe but should not drop too much at the meter coming into the house.
There may be some galvanized pipe between the street and the house causing the drop.

Bill
Yes there is a hose bib at the meter where we attached a pressure gauge. With no fixtures running it shows 60 psi at the meter. With 3 showers on it shows 20 psi at the meter. Do you think a booster pump would help?

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Re: Low water pressure/flow in house

Post by HomeStretch » Tue Oct 29, 2019 4:07 pm

barnaclebob wrote:
Tue Oct 29, 2019 1:21 pm
Are you sure that all upstairs showers aren't being supplied by one 1/2" pipe or something? I've got extremely high water pressure (maybe too high and I need to look into it) but as soon as you try to do two things at once in my house the water flow rate drops because my whole house is pretty much fed by a single 1/2" pipe.

That single skinny pipe splits 3 ways shortly after the main shutoff so I can probably put a 1" pipe up to that split and it will greatly improve the situation, just haven't gotten around to it yet.
+1 to check on this. We have high water pressure but had issues when we moved in with getting enough water pressure to two upstairs showers simultaneously. If you were in one shower and another was turned on, you could feel the lower flow in each shower. One skinny copper pipe was feeding the bathrooms. Plumber installed larger diameter pipe across open ceiling basement to where the pipe split off to each bathroom. Helped tremendously. No issue with two showers running simultaneously now.

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Re: Low water pressure/flow in house

Post by mpnret » Tue Oct 29, 2019 5:26 pm

Pete12 wrote:
Tue Oct 29, 2019 3:49 pm
billc23 wrote:
Tue Oct 29, 2019 3:27 pm
It may be a problem with the one inch copper into the house. Are you able to run a faucet near the meter and check the pressure?
The pressure drop occurs along the length of 1/2 inch pipe but should not drop too much at the meter coming into the house.
There may be some galvanized pipe between the street and the house causing the drop.

Bill
Yes there is a hose bib at the meter where we attached a pressure gauge. With no fixtures running it shows 60 psi at the meter. With 3 showers on it shows 20 psi at the meter. Do you think a booster pump would help?
Pressure drop to 20 psi at the meter is your problem, not skinny pipes feeding multiple showers. You need a local plumber who will be familiar with expexted PSI and flow rate of your water company.

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Re: Low water pressure/flow in house

Post by Cheez-It Guy » Tue Oct 29, 2019 6:46 pm

Image
Last edited by Cheez-It Guy on Tue Oct 29, 2019 8:43 pm, edited 1 time in total.

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Re: Low water pressure/flow in house

Post by Ramon » Tue Oct 29, 2019 7:11 pm

If the pressure gauge was installed close to the meter location, the pressure drop most likely occurred in the service line (the water pipe between the water main and the house.) This line may be clogged with corrosion products, especially if it is wholly or partially galvanized iron or the main shutoff valve could be partially closed or obstructed. The problem could possibly be in the water main itself. If the pressure were to fluctuate while no water is being used, this might be the cause. In any case, the booster pump is not a good idea. It could put a negative pressure on the service line and potentially draw contaminants in because of the negative pressure. In addition, the water supplier may not allow it.

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Re: Low water pressure/flow in house

Post by criticalmass » Tue Oct 29, 2019 9:57 pm

Low flow? I don't like the sound of that!

I would measure the pressure near the service entrance while running water, perhaps one sink open. Note how much the pressure drops with one sink running. If it drops more than a few PSI, there is likely a restriction before the gauge.

That restriction could be in the service line between your (future) house and the street. What is this pipe made of?

Galvanized steel is known to be fine for a few years, then it starts rusting from the inside out. The rust blocks the water flow like a clogged artery, so the pipe can't supply enough water to maintain pressure when there is high demand. Highly rusted galvanized pipes might only allow a trickle of water to go through, or less. It gets worse with time.
Last edited by criticalmass on Wed Oct 30, 2019 10:00 pm, edited 1 time in total.

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Re: Low water pressure/flow in house

Post by Cubicle » Tue Oct 29, 2019 11:17 pm

Also chiming in that it sounds more like a restricted flow problem than a pressure problem. A small drip can build to 60psi given enough pressure from the city & enough time. Ask neighbors as well.

Also, do check the shower heads. They might have that flow restrictor thingy in them. Might help if you are allowed to remove them.

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Re: Low water pressure/flow in house

Post by Pete12 » Wed Oct 30, 2019 6:57 am

Thanks everyone. To confirm, we have tested the pressure right at the water meter. It drops from 60psi to 20psi when all the showers are on. However it immediately goes back to 60psi when the showers are shut off. So does this sounds like a problem with the city water pressure rather than the service line?

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Re: Low water pressure/flow in house

Post by Smoke » Wed Oct 30, 2019 8:06 am

Pete12 wrote:
Wed Oct 30, 2019 6:57 am
Thanks everyone. To confirm, we have tested the pressure right at the water meter. It drops from 60psi to 20psi when all the showers are on. However it immediately goes back to 60psi when the showers are shut off. So does this sounds like a problem with the city water pressure rather than the service line?
Just out of curiosity, is the hose bib you are testing close to (at) the meter connected to a one inch line or a 1/2" line?
Arguing for the sake of arguing is something I am not going to engage in.

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Re: Low water pressure/flow in house

Post by billc23 » Wed Oct 30, 2019 8:52 am

It is the service line being obstructed or an issue with the valve at the street level.
Do the screens in the faucets need to be cleaned of sediment very often??

If it was the city water pressure then the neighbors water use would affect this house.

Bill

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Re: Low water pressure/flow in house

Post by Pete12 » Wed Oct 30, 2019 9:09 am

Smoke wrote:
Wed Oct 30, 2019 8:06 am
Pete12 wrote:
Wed Oct 30, 2019 6:57 am
Thanks everyone. To confirm, we have tested the pressure right at the water meter. It drops from 60psi to 20psi when all the showers are on. However it immediately goes back to 60psi when the showers are shut off. So does this sounds like a problem with the city water pressure rather than the service line?
Just out of curiosity, is the hose bib you are testing close to (at) the meter connected to a one inch line or a 1/2" line?
Hose bib is attached to 1 inch line. It appears the 1 inch line then goes on to feed the house, I assume the lines then go down to 1/2 inch somewhere in the walls upstairs but not able to know that yet as we haven't closed on the house.

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Re: Low water pressure/flow in house

Post by Pete12 » Wed Oct 30, 2019 9:10 am

billc23 wrote:
Wed Oct 30, 2019 8:52 am
It is the service line being obstructed or an issue with the valve at the street level.
Do the screens in the faucets need to be cleaned of sediment very often??

If it was the city water pressure then the neighbors water use would affect this house.

Bill
Thanks, we don't know about the faucet screens yet, we have not closed on the house yet. I will try and talk to the new neighbors as well....

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Re: Low water pressure/flow in house

Post by RickBoglehead » Wed Oct 30, 2019 9:11 am

I still come back to the issue perhaps being a non-issue.

Pressure is 60psi. Open up THREE shower heads and pressure is 20psi.

Question - what did the engineer say it SHOULD have been with THREE shower heads running?

As I stated earlier, I've never heard of anyone being able to take 3 showers at the same time...
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Re: Low water pressure/flow in house

Post by Texanbybirth » Wed Oct 30, 2019 9:19 am

RickBoglehead wrote:
Wed Oct 30, 2019 9:11 am
I still come back to the issue perhaps being a non-issue.

Pressure is 60psi. Open up THREE shower heads and pressure is 20psi.

Question - what did the engineer say it SHOULD have been with THREE shower heads running?

As I stated earlier, I've never heard of anyone being able to take 3 showers at the same time...
Slightly off topic, but we have easily had 3 showers running simultaneously in our house. We only have three bathrooms so I can't check if any more would work, but we were using the kitchen sink to wash dishes at the same time. Our master bath also has two shower heads in it.

(Now, we almost never have that happen - using 3 showers. However, we have better water pressure in our house than I've ever seen in any house I've ever been in. Of course that could just mean our pipes will burst but at 37 years old it hasn't happened to our house yet.)
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Re: Low water pressure/flow in house

Post by Pete12 » Wed Oct 30, 2019 9:26 am

RickBoglehead wrote:
Wed Oct 30, 2019 9:11 am
I still come back to the issue perhaps being a non-issue.

Pressure is 60psi. Open up THREE shower heads and pressure is 20psi.

Question - what did the engineer say it SHOULD have been with THREE shower heads running?

As I stated earlier, I've never heard of anyone being able to take 3 showers at the same time...
I sure hope you are right. I think looking for sediment in the screens will be telling. The engineer would not comment on what the pressure should be at maximum flow, only to say "it depends."

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Re: Low water pressure/flow in house

Post by RickBoglehead » Wed Oct 30, 2019 9:28 am

Pete12 wrote:
Wed Oct 30, 2019 9:26 am
RickBoglehead wrote:
Wed Oct 30, 2019 9:11 am
I still come back to the issue perhaps being a non-issue.

Pressure is 60psi. Open up THREE shower heads and pressure is 20psi.

Question - what did the engineer say it SHOULD have been with THREE shower heads running?

As I stated earlier, I've never heard of anyone being able to take 3 showers at the same time...
I sure hope you are right. I think looking for sediment in the screens will be telling. The engineer would not comment on what the pressure should be at maximum flow, only to say "it depends."
Interesting. We've hired home inspectors, but never an "engineer".
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Re: Low water pressure/flow in house

Post by goblue100 » Wed Oct 30, 2019 9:46 am

RickBoglehead wrote:
Wed Oct 30, 2019 9:11 am

As I stated earlier, I've never heard of anyone being able to take 3 showers at the same time...
At my house we can run all 3 showers(2 up, 1 down) with a minimal drop in water pressure. But my house was built 80 years after the OP's, so I assume standards have changed.
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Re: Low water pressure/flow in house

Post by mpnret » Wed Oct 30, 2019 10:12 am

The pressure dropping down to 20 psi on the 1" line entering the house is an indication the problem is not in your house put at the entry point or before. Water meter, entry line, street, water company? Dropping down to 20 psi is certainly not normal in any of the many areas that I have lived in but it is possible to be normal for yours. Did you try contacting the water company to see what they consider normal? Maybe they will come out and check it. Isn't sale contigent on home inspection? Maybe seller will check it out.

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Re: Low water pressure/flow in house

Post by miketownsend33 » Wed Oct 30, 2019 10:15 am

This sounds exactly like the problem I had at my multi level house. PSI at hose bib was ~60psi, but dropped when faucets were open and I had very weak flow on upper levels or when multiple people were showering, washing clothes etc.

It turned out the problem was a bad gate valve controlling the main water supply. It wasn't letting sufficient water into the supply line hence the low pressure when demand increased. Solution was to get a plumber to replace the gate valve with a ball valve. Maybe see if this is your issue?

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Re: Low water pressure/flow in house

Post by neilpilot » Wed Oct 30, 2019 10:28 am

Pete12 wrote:
Wed Oct 30, 2019 9:26 am
RickBoglehead wrote:
Wed Oct 30, 2019 9:11 am
I still come back to the issue perhaps being a non-issue.

Pressure is 60psi. Open up THREE shower heads and pressure is 20psi.

Question - what did the engineer say it SHOULD have been with THREE shower heads running?

As I stated earlier, I've never heard of anyone being able to take 3 showers at the same time...
I sure hope you are right. I think looking for sediment in the screens will be telling. The engineer would not comment on what the pressure should be at maximum flow, only to say "it depends."
Assuming the pressure gauge is connected to the hose bib immediately adjacent to the service line (meter ext) and there's no flow out the bib, then a partially blocked screen and the line size connecting the hose fitting would not effect the pressure reading at all.

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Re: Low water pressure/flow in house

Post by Smoke » Wed Oct 30, 2019 10:32 am

Just as an observation, I had my "main" from the street replaced about 4 yrs ago with 3/4, I have 100 to 110 lbs pressure at the street so I have a pressure reducer bringing it down to 58 lbs.

I just now connected a pressure gauge to a 1/2" bib and it reads 58 lbs with no water running, I turned on one bathroom sink, pressure dropped to 40 lbs.

I would not think it unreasonable for a pressure drop with 3 showers running to drop to 20.
Arguing for the sake of arguing is something I am not going to engage in.

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Re: Low water pressure/flow in house

Post by mpnret » Wed Oct 30, 2019 11:35 am

Smoke wrote:
Wed Oct 30, 2019 10:32 am
Just as an observation, I had my "main" from the street replaced about 4 yrs ago with 3/4, I have 100 to 110 lbs pressure at the street so I have a pressure reducer bringing it down to 58 lbs.

I just now connected a pressure gauge to a 1/2" bib and it reads 58 lbs with no water running, I turned on one bathroom sink, pressure dropped to 40 lbs.

I would not think it unreasonable for a pressure drop with 3 showers running to drop to 20.
And while you are all hooked and ready to go, you couldn't open up some more water users and see what happens? (doesn't have to be showers). Mine stays steady at 60 psi but I have a well pump so not a good comparison.

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Re: Low water pressure/flow in house

Post by Smoke » Wed Oct 30, 2019 11:50 am

mpnret wrote:
Wed Oct 30, 2019 11:35 am
Smoke wrote:
Wed Oct 30, 2019 10:32 am
Just as an observation, I had my "main" from the street replaced about 4 yrs ago with 3/4, I have 100 to 110 lbs pressure at the street so I have a pressure reducer bringing it down to 58 lbs.

I just now connected a pressure gauge to a 1/2" bib and it reads 58 lbs with no water running, I turned on one bathroom sink, pressure dropped to 40 lbs.

I would not think it unreasonable for a pressure drop with 3 showers running to drop to 20.
And while you are all hooked and ready to go, you couldn't open up some more water users and see what happens? (doesn't have to be showers). Mine stays steady at 60 psi but I have a well pump so not a good comparison.
Well yes I could have, however my plumbing may not be the same setup as others. That is why I only opted for one faucet. It would be similar no matter how everyone's plumbing is set up. Large trunk line with feeders, home run setup, or all 1/2 inch after the main.
The results would be different with more than one faucet open depending on setup.
I also have a water softener and two whole house filters to run thru first as well, but my secondary prv is after those, I have two prv's one at the street and one in the basement to step down from the 100 - 110 pressure.

Yes a well pump has a pressure tank similar to a smaller expansion tank, which I have, and I made sure the expansion tank was depressurized by running the water a min or two first.
Arguing for the sake of arguing is something I am not going to engage in.

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Re: Low water pressure/flow in house

Post by GrowthSeeker » Wed Oct 30, 2019 11:54 am

Interested in what the flow rates are (GPM) in various locations:
Near entry into house
Various faucets tested alone
2 showers at a time
3 showers at a time

Also pressure readings for 1 and for 2 faucets being open.

Do pressure valves at entry to house govern flow rate in addition to restricting pressure?

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Smoke
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Re: Low water pressure/flow in house

Post by Smoke » Wed Oct 30, 2019 12:07 pm

GrowthSeeker wrote:
Wed Oct 30, 2019 11:54 am
Interested in what the flow rates are (GPM) in various locations:
Near entry into house
Various faucets tested alone
2 showers at a time
3 showers at a time

Also pressure readings for 1 and for 2 faucets being open.

Do pressure valves at entry to house govern flow rate in addition to restricting pressure?

Eight AAA batteries in series is 12 volts, but won’t start a car.
You are correct, flow rates are more important than PSI.
You can have a very high PSI but very low flow rate.
Like putting your thumb over the end of a hose, higher PSI but restricted flow.
No thumb, lower PSI but higher flow.
Arguing for the sake of arguing is something I am not going to engage in.

LawEgr1
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Re: Low water pressure/flow in house

Post by LawEgr1 » Wed Oct 30, 2019 12:57 pm

I'm a Professional Engineer, Chemical, that works with complicated pipe flow systems in chemical plants on a good day when I can actually do engineering instead of managing and $. Governing equations and principles are identical from a chemical / oil plant to the residential systems, and much less complicated.

Swapping valve types is inconsequential for this analysis, trust me, it'll be a waste of your $. Only do it and replace w/ a like for like valve is the valve itself is bad. Plus follow your local authority having jurisdiction and code requirements.

In lieu of not knowing flow rates, all this junk below is pressure related.

There are several missing pieces of information in this thread, namely because we are not at your house, but also some incorrect information and just blanket statements.

- Configuration of the piping system absolutely does matter. That means the directions, height changes and fittings involved, along with diameter. This is essentially what everything is governed off of, so anybody doing this 'test' for you at their house is liable to only a baseline, not an exact, comparison. (test of reasonableness). In this case, it's liable to be the culprit.

- Reduction in pipe diameter impacts pressure drop EXPONENTIALLY, not linearly. Therefore, any un-necessary long runs of 0.5" are going to kill your available pressure for flow.

- There is always pressure drop, regardless of pipe size, not only in 'specific sections'. It's just the amount that varies per foot that changes pending a variety of factors. It's impossible to not have frictional losses. If anyone says so, they lie or don't know what they're talking about.

- we know nothing of the water main system to the house.


Change in elevation (Delta Z) - Automatic pressure loss - Thanks gravity!

For each 2.31 feet of elevation change from that 60 psi, you will have a reduction in pressure by 1 psi. Example: Your elevation change from the 60 psi point to the shower head is 20 feet. Therefore (20 feet / 2.31) = an automatic 8.65 psi drop without doing anything. It's just how it works. So, if you had 60 psi, no frictional losses / velocity losses / fittings, etc., had 1 shower and used it, you'd have 52 psi left. (that scenario isn't possible, just an example). Is the 1" main on the bottom and then everything goes up from there? Or did they run the 1" upstairs then tee off from there?

So, extrapolating a bit, you can have a few situations occurring:

1) The piping is in a split flow format from the 1" main, which means that it's just like a parallel circuit. You're pressure drop will increase significantly shall you run all 3 showers at the same time. The pressure drop between each branch will be identical to the other regardless of length / ID, and the velocities of each will adjust to accommodate.

2) You have an inordinate amount of 1/2" piping, increasing to 1" then tee'ing off to 1/2" as needed would reduce dP and increase flow to each end user. This would result in rework of the system.

3) Service line from the water main, as others have pointed out, could be galvanized. If so, galvanized >50 years is extremely liable to have smaller ID than what it was originally intended, further inhibiting your ability to maintain pressure.

4) Verify all VALVES are WIDE open not causing a restriction. This would crush your dP in a small ID system

5) Verify you have NO LEAKS


I will also tell you the following:

As rough rules of thumb, per each 100 feet of 1" pipe you have:

FLOW RATE (GPM) / REDUCTION IN PSIG
10 / 3
20 / 11

For each 100 feet of 1/2", you have:

FLOW RATE (GPM) / REDUCTION IN PSIG
1 / 0.61
5 / 11
10 / 42
15 / 92

Those are quick and dirty rules of thumb that could get you in the ball park. This is a super easy analysis once someone knows the lengths, diameters and configuration of the piping network.

I have a suspicion that both your incoming flow is lower than desired, but not bad, and you have unnecessary amounts of smaller bore pipe which then results in this post.

-LE1

mrc
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Re: Low water pressure/flow in house

Post by mrc » Wed Oct 30, 2019 4:33 pm

Given some of these posts, I wonder if the mains is all the way open. This sounds like a classic part-open gate valve. You'd have high pressure with no flow, and pressure would plummet with faucet(s) open.
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criticalmass
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Re: Low water pressure/flow in house

Post by criticalmass » Wed Oct 30, 2019 10:04 pm

Pete12 wrote:
Wed Oct 30, 2019 6:57 am
Thanks everyone. To confirm, we have tested the pressure right at the water meter. It drops from 60psi to 20psi when all the showers are on. However it immediately goes back to 60psi when the showers are shut off. So does this sounds like a problem with the city water pressure rather than the service line?
My best guess based on your description is the service line can’t supply enough flow to meet the demand of three outlets without a very large reduction in pressure.

If the service line is 1” then it is probably restricted somewhere because 1” should be plenty.

If the city pressure was an issue, then your house would suffer low pressure whenever your neighbor took showers, used a washing machine, etc. Is the main valve(s) fully open? Is the meter working properly?

wilked
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Re: Low water pressure/flow in house

Post by wilked » Wed Oct 30, 2019 10:16 pm

As a few of the others noted, the problem is upstream of your pressure measurement, not downstream.

There is a restriction somewhere on the 1” feed or there is an overall city water pressure issue. My guess is the former.

Do verify that your shower heads push about 2 gpm. If it’s way more (say 5 gpm) that may be it, but I doubt it.

The talk about showers being fed off a common 1/2” line wouldn’t matter - that might be low flow in the showers but it wouldn’t result in a pressure drop at the main.

You’ve got a restriction. Likely corrosion in the line. Good luck

Edit to add: I am a seasoned ChemEng that does this stuff daily in a manufacturing plant

CurlyDave
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Re: Low water pressure/flow in house

Post by CurlyDave » Wed Oct 30, 2019 10:50 pm

wilked wrote:
Wed Oct 30, 2019 10:16 pm
As a few of the others noted, the problem is upstream of your pressure measurement, not downstream.

There is a restriction somewhere on the 1” feed or there is an overall city water pressure issue. My guess is the former.

Do verify that your shower heads push about 2 gpm. If it’s way more (say 5 gpm) that may be it, but I doubt it.

The talk about showers being fed off a common 1/2” line wouldn’t matter - that might be low flow in the showers but it wouldn’t result in a pressure drop at the main.

You’ve got a restriction. Likely corrosion in the line. Good luck

Edit to add: I am a seasoned ChemEng that does this stuff daily in a manufacturing plant
There is one other possibility you should check. What size is you water meter?

When I rebuilt my house in CA after a fire a few years ago, the original structure had a 1/2" water meter and 3/4" main line to the house.

I had to upsize to 3/4" meter and 2" line to the house for fire sprinklers, but I discovered along the way that the water company connection charge is based on the size of the meter. 1/2" was about $30/month, 3/4" was closer to $60/month.

But, the water meter was almost always smaller than the feed line. And because of the economics of the situation, there was a big incentive to undersize the water meter.

The other things that can mimic an obstruction are the valve at the street being only partly open, and a failing water meter. Of course, corrosion in the main feed line is another possibility.

wilked
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Re: Low water pressure/flow in house

Post by wilked » Thu Oct 31, 2019 4:50 am

^ good point

Another thing you could do is this if you want to really define this thing:

Go to Home Depot and the aisle with all the bits and plumbing fittings, fashion a tee that will attach your that hose bib. One side of the tee will be your pressure gauge, the other side add a gate valve and small section of hose.

Get yourself a 5 gallon bucket, and then make a table on some paper. Two columns, first is flow second is pressure.

Vary the valve and collect pressure reading at: 1 gpm, 3 gpm, 5, 10, 15, 20. If you post that data I can estimate your pressure drop you are losing.

Anyway, that would be good data to show to the city water, and ask them to check their end. If their end checks out you are likely going to want a Boroscope.

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Re: Low water pressure/flow in house

Post by GrowthSeeker » Thu Oct 31, 2019 9:17 am

1. Would the city come and check even if you don't have any data?

2. Could it be that at some point, the incoming water pressure was too high, either because there was no pressure reducing valve near the meter or maybe it was malfunctioning; and rather than install/fix the pressure reducing valve, they started closing the "curb valve" until the pressure read 60? Is that a "thing"?
Just because you're paranoid doesn't mean they're NOT out to get you.

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Pete12
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Re: Low water pressure/flow in house

Post by Pete12 » Thu Oct 31, 2019 9:39 am

Thank you everyone for your responses, I am very grateful for all the expertise and experience. I also spoke to a local plumber who was recommended to me.

So the general consensus seems to be that the main factor is the incoming supply from the street. Either a blocked pipe, a faulty valve, or just general issues with the city pressure.

I ran this by the plumber who recommended we hold off installing a booster pump for now, since the water is usable. He said if there is an issue with the incoming line (rather than a problem with the city pressure) then it would be a band-aid and could even cause the incoming pipe to fail if it is indeed partly galvanized and rusting, due to the negative pressure created by the pump.

He recommended that after we close on the house we immediately sign up for the city's water line insurance ($5/month), wait 30 days for it to kick in, then call the city to file a complaint about the pressure. If they investigate and find it's a problem with our line, the replacement would be covered by the insurance. If it's not the line and is just a general pressure problem in the neighborhood, then installing a booster pump would help.

Does this sound like a reasonable approach?

Once we are actually in the house I can run some tests for flow rate etc. as posters have mentioned.

HomeStretch
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Re: Low water pressure/flow in house

Post by HomeStretch » Thu Oct 31, 2019 9:47 am

Have you reviewed the water line insurance policy to be sure it would cover all your costs to repair anything between the street main line and your house including landscape repair, etc.? Is the house on septic or sewer? In our area, properties on septic are ineligible for the insurance. Has the plumber actually seen the insurance claim strategy in use and work?

Your plan is one way to go. Personally I’d be reluctant to close on the property without knowing the issue/cost and without the Seller correcting the issue, if major. A faulty or partially closed valve is minor to repair. Digging up and replacing a failed pipe from the street to house is major.

mpnret
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Re: Low water pressure/flow in house

Post by mpnret » Thu Oct 31, 2019 11:02 am

Maybe the seller already has the insurance you mentioned. Regardless, why haven't you approached the seller on correcting the issue? My past real estate contracts where a home inspection was involved had some wording like seller having option to correct any issues or cancel the contract. At least ask you agent for advice. Maybe get a concession from the seller. Otherwise your idea sounds technically sound.

wilked
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Re: Low water pressure/flow in house

Post by wilked » Thu Oct 31, 2019 11:43 am

Where are you on the home buying process? Accepted offer? Past the inspection period? Have you passed papers?

I think the idea of insurance is a good one if it would cover replacement of the water supply from the city main.

Based on what you described I'd assume $5000-10,000 for a full replacement of the line, likely toward $10K

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Re: Low water pressure/flow in house

Post by GrowthSeeker » Thu Oct 31, 2019 11:56 am

Insurance might not cover this “pre-existing condition”.
Just because you're paranoid doesn't mean they're NOT out to get you.

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