Loss of water pressure when using hot water

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canderson
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Loss of water pressure when using hot water

Post by canderson »

In the past few days we have experienced a loss of water pressure the hotter the water is. It is in our master shower specifically, but I can mimic it in multiple sinks upstairs and downstairs. There is still pressure, but I'd guess about half of what it is when set to cold only. Also, the water temp doesn't fluctuate nearly as precise as it did before this problem. Once hot, it stays that temp in the shower until it's about 10 percent away from being off completely then starts to flip to cold.

All our faucets are Moen single-handle units. I originally thought the shower cartridge might be bad, but then realized sinks suffer the same phenomenon.

If it helps, our water heater is a 50 gal. gas unit. Our house is three stories, 2100 sq ft and is coming up in May on 10 years old.

Anyone have any guesses as to what might cause this?
Stonebr
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Re: Loss of water pressure when using hot water

Post by Stonebr »

Because the pressure change affects the whole house, you probably want to check the hot water tank itself. The fluctuation in temperature would also implicate the tank. If it, like the house, is 10 years old, you may be due for a new one.

Here's a link to wikiHow with some info on troubleshooting low water pressure. I suspect you'll end up talking with a plumber. :(

http://www.wikihow.com/Troubleshoot-Low-Water-Pressure
"have more than thou showest, | speak less than thou knowest" -- The Fool in King Lear
livesoft
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Re: Loss of water pressure when using hot water

Post by livesoft »

We have Moen fixtures as well. Perhaps the washers in the valves expand when the water heats them up and thus the expanded washers restrict the flow just as if you turned the faucet to lower flow?

It is also possible that the water going into the heater is getting restricted. There is usually an inlet valve in the pipe where cold water goes into the water heater. It is partially closed? Does it get hot from thermal transfer from the water heater? Does it get cold because the temperature of the water going into the house is colder during winter? I'd go check that valve myself first.

Is there debris internally blocking the exit port of the heater? Maybe learn to flush the heater?
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Yooper
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Re: Loss of water pressure when using hot water

Post by Yooper »

I agree it probably isn't cartridge if the symptoms are throughout the house, but for informational purposes only I've had outstanding experiences when dealing with Moen customer service. I called them just to get the part number for a cartridge so I could purchase one (I was a bit confused on which model I had) and they basically said, "No, we'll send you a replacement free of charge." Classy.
Topic Author
canderson
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Re: Loss of water pressure when using hot water

Post by canderson »

Thanks everyone. All looks good regarding valves. I'll call the plumber tomorrow, I'm off Monday so should be able to get a visit then.

In case the water heater is on its last legs, any advice on new ones? Only requirement is I'd like a digital temp reading where we can set vacation mode easily. We live in Pennsylvania so a cold climate.m
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joe8d
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Re: Loss of water pressure when using hot water

Post by joe8d »

"No, we'll send you a replacement free of charge."
Same experience with Moen.
All the Best, | Joe
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Toons
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Re: Loss of water pressure when using hot water

Post by Toons »

"One does not accumulate but eliminate. It is not daily increase but daily decrease. The height of cultivation always runs to simplicity" –Bruce Lee
CP4641
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Re: Loss of water pressure when using hot water

Post by CP4641 »

I had a similar problem and it was due to some hard plastic that had flaked off in my hot water heater. The flakes went through the pipes and lodged in the valves. I noticed some white flakes when I removed a screen on one of the faucets. Another way to check is to disconnect the hose to the washing machine and see if there is any blockage lodged in the inlet screen. Eventually the flakes worked their way through the system after I replaced the tank.
Good luck.
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Re: Loss of water pressure when using hot water

Post by Mudpuppy »

Toons wrote:FYI:

Whirlpool Water Heater :happy

http://www.lowes.com/pd_345709-135-ES50 ... 490&rpp=32
After how Whirlpool warranty service treated my elderly parents when their 6 month old water heater went on the fritz, reading about how many other people had issues with Whirlpool hot water heaters breaking early, and seeing that they had a class action lawsuit about manufacturing defects in the hot water heaters, I could not recommend buying a Whirlpool hot water heater. And I say this as someone who has chosen to purchase Whirlpool for a wide variety of other appliances (fridge, dishwasher, washer, and dryer). It's been years since this happened, and I still can't write out how badly they treated my parents (and me when I tried to call on my parents' behalf) without having an unhealthy spike in blood pressure.

Unless Whirlpool no longer uses American to manufacture their hot water heaters, I would look elsewhere. I'd recommend going with one of the brands you can get through a plumber, like Bradford White or Rheem. I just don't like the idea of messing with something hold dozens of gallons of water on the other side of the wall from my hardwood floors. Nor does heating water on the stove to have warm bathing water while waiting for a repair/replacement sound particularly appealing.
saladdin
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Re: Loss of water pressure when using hot water

Post by saladdin »

If it's multiple sinks then it has to be a leak in the main line or the tank itself.

Did you lose cold pressure?

Loss of pressure to me would make me immediately look under the house and the tank for a leak. Then I would go to the main and see if it's leaking. I would turn off every faucet and see if the meter was still spinning to see if the leak is in the main line underground.

If you have a steady supply of hot water then it turns cold I would think you have a heating element going bad. Cold water from a water heater means no heat.
rustymutt
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Re: Loss of water pressure when using hot water

Post by rustymutt »

I'd suggest that you read up on flushing your hot water heater. I flush out mine every 4 years. Simple to do. Messy though for the hose drains into our floor drain. You can find instructions online.
Also helps the tank to not rust out as badly. You wouldn't believe the crap that flushes out of it.
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Topic Author
canderson
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Re: Loss of water pressure when using hot water

Post by canderson »

saladdin wrote:If it's multiple sinks then it has to be a leak in the main line or the tank itself.

Did you lose cold pressure?

Loss of pressure to me would make me immediately look under the house and the tank for a leak. Then I would go to the main and see if it's leaking. I would turn off every faucet and see if the meter was still spinning to see if the leak is in the main line underground.

If you have a steady supply of hot water then it turns cold I would think you have a heating element going bad. Cold water from a water heater means no heat.
No loss on cold pressure. I actually did look at the meter and it doesn't move at all when all faucets are shut.

Regarding a leak, we are on concrete slab so not easy to look under the house. There is no visible leak in the HVAC closet.

rudtymutt, we've been told draining the water heater provides little benefit and can expedite the tank failing. I have read and known those that drain then, but I've had three different plumbers advice against it here with our water.
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Bengineer
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Re: Loss of water pressure when using hot water

Post by Bengineer »

One way to test whether the problem is the supply from the heater or the fixtures is to hook a hose to the hot supply for the washing machine and measure the flow with the valve wide open, see if it drops off, vs the cold side etc. Careful!
tivattom
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Re: Loss of water pressure when using hot water

Post by tivattom »

After 10 years I would guess that the thermal expansion tank may have failed if you have one. This is the 2 gallon jug-looking thing on the pipe near your water heater.

A failed expansion tank can result in increased hot water pressure when the water heater has been heating for a while (like overnight). Then once the hot water is used the pressure returns to normal levels. Its pretty easy to check, find the expansion tank and there is a pressure valve on the top like you would find on a tire. Press the release on the valve to let a little air out of the expansion tank. If water comes out instead the bladder inside the thermal expansion tank is ruptured and the tank needs to be replaced. You have to be careful as the water that can come out will likely be hot.

Another way to test it is to buy a pressure gauge with a needle that remember the peak pressure. You would put this on a faucet overnight, like a utility tub, with the hot side of the faucet open. Measure the maximum pressure overnight while no hot water is being used and it has time to build up. If the overnight pressure is much higher than the normal daily pressure then this indicates a failed thermal expansion tank, too.

These can be bought at home depot and lowes and come with instructions on how to replace them-- you have to match the expansion tank bladder pressure to the normal water pressure you get in your main water line. It is recommended to inflate the bladder with a hand pump because using an air compressor may inflate too quickly and rupture the new bladder inside the tank.

Good luck!
Last edited by tivattom on Fri Jan 16, 2015 10:09 am, edited 1 time in total.
Yooper
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Re: Loss of water pressure when using hot water

Post by Yooper »

canderson wrote:rudtymutt, we've been told draining the water heater provides little benefit and can expedite the tank failing. I have read and known those that drain then, but I've had three different plumbers advice against it here with our water.
Only you know your water, and I'm sure what the plumbers said to you made sense or you would have questioned it, but for the life of me I can't think of how draining a tank could possibly expedite its failing. All you're doing is letting any accumulated crud on the bottom wash out. But perhaps that's why I'm not a plumber (grin).
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Epsilon Delta
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Re: Loss of water pressure when using hot water

Post by Epsilon Delta »

One possibility that has not been mentioned is a failed thermostatic mixing valve. I believe these are standard practice in Canada and the UK at the hot water tank. While they are rare in the US you might find one. If you look at enough plumbing you will find all sorts of weird and wonderful things, and find that all of them can fail in weird but not wonderful ways. There is no substitute for a hands on inspection.

http://www.watts.com/pages/learnAbout/t ... asp?catId=
derosa
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Re: Loss of water pressure when using hot water

Post by derosa »

type your systems into google and you should get some responses.
Topic Author
canderson
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Re: Loss of water pressure when using hot water

Post by canderson »

tivattom wrote:After 10 years I would guess that the thermal expansion take may have failed if you have one. This is the 2 gallon jug-looking thing on the pipe near your water heater.

A failed expansion tank can result in increased hot water pressure when the water heater has been heating for a while (like overnight). Then once the hot water is used the pressure returns to normal levels. Its pretty easy to check, find the expansion tank and there is a pressure valve on the top like you would find on a tire. Press the release on the valve to let a little air out of the expansion tank. If water comes out instead the bladder inside the thermal expansion tank is ruptured and the tank needs to be replaced. You have to be careful as the water that can come out will likely be hot.

Another way to test it is to buy a pressure gauge with a needle that remember the peak pressure. You would put this on a faucet overnight, like a utility tub, with the faucet open. Measure the maximum pressure overnight while no hot water is being used and it has time to build up. If the overnight pressure is much higher than the normal daily pressure then this indicates a failed thermal expansion tank, too.

These can be bought at home depot and lowes and come with instructions on how to replace them-- you have to match the expansion tank bladder pressure to the normal water pressure you get in your main water line,. It is recommended to inflate the bladder with a hand pump because using an air compressor may inflate too quickly and rupture the new bladder inside the tank.

Good luck!
We do indeed have an expansion tank. I bet you are right! I'm legally blind however so won't be messing with it as it is hard to reach and higher than my shoulders so I can't get to it to see well.

The only weird thing is the morning pressure isn't any better than at night.

Plumber coming first thing Monday.
Terraplane
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Re: Loss of water pressure when using hot water

Post by Terraplane »

In a prior home we had, built in the '40's, we had lime/calcium buildup in the hot water lines and clog them. When we cut them out to replace, they looked like clogged arteries! New pipes fixed that. The cold lines were OK.

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saladdin
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Re: Loss of water pressure when using hot water

Post by saladdin »

Terraplane wrote:In a prior home we had, built in the '40's, we had lime/calcium buildup in the hot water lines and clog them. When we cut them out to replace, they looked like clogged arteries! New pipes fixed that. The cold lines were OK.

Terraplane
Sounds like you have galvanized pipes and not cpvc, like me. My house was built in the 50's and am waiting for that to happen to ours.
FRANK2009
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Re: Loss of water pressure when using hot water

Post by FRANK2009 »

I noticed the same lack of hot water pressure in my home too. It was solved when a new heating system was installed, including a new expansion tank, as mentioned. Also, everything including the radiators were bled by my able and experienced heating contractor. The only downside is I don't want to get out of shower.
Topic Author
canderson
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Re: Loss of water pressure when using hot water

Post by canderson »

Update!

Plumber came and solved the issue. Turns out it was a dielectric nipple failure in the cold water supply to the heater. He first replaced the hot water dielectric nipple but the symptoms didn't change.

Expansion tank is in good shape, he said, as is the water heater itself.

Other than the smoke alarms going off twice due to pipe soldering, all went well. :)
livesoft
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Re: Loss of water pressure when using hot water

Post by livesoft »

The cynic in me tells me they knew it was the cold water supply, but did the hot-side first so they could get you to pay for twice the work.
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Kenkat
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Re: Loss of water pressure when using hot water

Post by Kenkat »

Ah, the ol' dielectric nipple.

Sometimes it's worth bringing in an expert...
Topic Author
canderson
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Re: Loss of water pressure when using hot water

Post by canderson »

livesoft wrote:The cynic in me tells me they knew it was the cold water supply, but did the hot-side first so they could get you to pay for twice the work.
Ha! I'd guess no, this guy has given us all sorts of supplies with no costs over the years, he's not one to screw us over (I don't believe at least!).
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