Low water pressure except after running hot water

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Kevin Irwin

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Hey all, we have general low water pressure at all outlets in the house including toilets and showers. The problem is persistent EXCEPT when you use a faucet immediately after running the hot water anywhere else in the house. In fact, after running hot water somewhere in the house there is a pretty strong burst of water pressure which quickly subsides. We also get banging in the pipes after that burst of pressure.

Any thoughts what might be causing this?

Thanks!

Kevin Irwin
Little Rock, USA
 

FullySprinklered

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Are you on a well? Do you have a hot water recirculation system? Do you have galvanized water pipes? Are you just making this up?
 

Reach4

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When did the problem start -- right after your new water heater was installed?
 

Kevin Irwin

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Water heater is 8-10 years old. City water. We have lived here 10 months and it has been a problem the entire time. Not sure about galvanized pipes. No, I'm not making this up but I do know a good story about a bear and a rabbit if you want to hear it. ;-)
 

Reach4

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I am not a pro. Starting with something easy to do, I suggest that you get a pressure gauge that screws to a garden hose thread. These are typically $10 to $20. Check the pressure that you have at the water heater drain when you have a problem. (screw gauge on, open drain valve, take readings during problem, close drain valve, remove gauge) Check the pressure at an outside hose outlet when you have a problem. Maybe you have that thread on your laundry tub, or you can get to the washing machine hose connectors easily.

Is there any plumbing device plumbed in near the water heater that you don't recognize as a 2-port valve? Is there a device with 3 ports? Maybe post a picture of piping to and near the water heater. To do that, either put a link to a website with the picture, or reduce the picture size to 800 pixels in the biggest dimension and "Upload a File".

You can stick a magnet to galvanized pipes.
 

FullySprinklered

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Water heater is 8-10 years old. City water. We have lived here 10 months and it has been a problem the entire time. Not sure about galvanized pipes. No, I'm not making this up but I do know a good story about a bear and a rabbit if you want to hear it. ;-)
Was the rabbit named Charmin by any chance? Hope you get it figured out. A lot of pressure, venting, and odor problems are hard to figure. I get whipped probably half the time on those, but I always want to know what it is. Dollar says it's a pressure issue associated with the PRV, expansion tank, or some add-on contraption. They didn't pull the feed for the water heater off the main supply upstream of the PRV, by any chance?
 

Smooky

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I think you have more than one issue. The burst of pressure after running the hot water may be from a swing check installed incorrectly such as on it back in the horizontal position or a swing check in the vertical position with normal flow from the ceiling down. When you first turn on the cold, hot water backs up through the check valve until there is enough flow to slam the valve shut. This could explain the suden burst and the noise. As far as why less water pressure in the cold maybe a valve is partly closed or clogged etc
 

hj

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We could GUESS all day about what COULD be happening, (and some of these guesses are quite "creative" and improbable), and even then not come up with the correct answer. Someone has to be there to see the conditions while it is happening in order to determine WHAT is happening and why. THEN they can come up with a solution.
 

KevinPrz

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easy, the flux capacitor needs precisely 1.21 gigawatts or you'll never get anywhere.
 

Plumber69

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Hey all, we have general low water pressure at all outlets in the house including toilets and showers. The problem is persistent EXCEPT when you use a faucet immediately after running the hot water anywhere else in the house. In fact, after running hot water somewhere in the house there is a pretty strong burst of water pressure which quickly subsides. We also get banging in the pipes after that burst of pressure.

Any thoughts what might be causing this?

Thanks!

Kevin Irwin
Little Rock, USA
Take a picture of your main shutoff in your house, old gate valves tend to break apart and get stuck in the valve itself of the piping
 
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