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Old 10-26-2015, 07:36 PM   #1
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Intermittent Low Water Pressure Mystery

I live in a 2-story, 1.5 bath home which a 6-8 months ago started having a strange symptom of intermittent low water pressure.

The Symptom

Randomly, the whole house will have very low water pressure. The flow is noticeably slow, less than half the normal flow rate. Both the hot and cold water lines are affected. It lasts for anywhere from < 5 seconds to < 10 minutes, at which point both hot and cold will immediately return to its full flow rate. Whenever one faucet shows symptoms, all faucets and toilets are affected (whole house). It occurs frequently (at least once a day). I usually let the water run until it resolves itself. Nothing I do seems to have an effect on the symptom including running multiple faucets concurrently or cycling the water on/off/on/off in any order or timing. Sometimes when it resolves I hear a thud/pang, which a co-worker told me might be the sound of a "water hammer".

Action Taken

I've looked for leaks multiple times, both inside and outside where the water pressure regulator is. I can't find any evidence of them. There is a small water damage around one section of pipe in the outside closet where the water heater and water pressure regulator is, but I think that is a small roof leak. During a time when the symptom was reproduced I observed this area and it was bone dry.

Things to Know

Our water bills are low, and they're very similar to the past 5 years we've lived in this house without this symptom. This further supports the reasoning that this is not leak related.

Our house has polybutylene, so i'm hesitant to raise the water pressure at the water pressure regulator for any reason. I've never adjusted the water pressure, and when it's flowing normally it has an expected "good flow" not too strong or weak.


I suspect the water pressure regulator is failing. When those fail do they fail open or closed?

What are other possible causes for this issue?

What is the sound I'm hearing? Is it a water hammer?

Thanks a lot to everyone who has read this and responds with helpful ideas or information!
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Old 10-26-2015, 07:49 PM   #2
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I agree, It's possible the water pressure regulator may need servicing, adjusting or replacing.

Sounds like it could be water hammer.

What is the current water pressure reading? Good to check at different times of day.

Please wait for the plumbers to respond. Thanks.
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Old 10-26-2015, 08:05 PM   #3
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since you are on a municipal feed, have you checked with a neighbor for possible similar
pressure loss?
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Old 10-26-2015, 08:19 PM   #4
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how old is the pressure regulator..? most likely the regulator needs replaced since it effects the whole house...
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Old 10-26-2015, 10:00 PM   #5
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I'm with Ben... I think its simply the PRV.

I have not exactly experienced the same issue/symptoms, but those valves are a little complex and do fail with both their springs and crud. (I think some of them have a screen that can be cleaned... but I have just bit the $40 bucks and replace with new.)

Good luck
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Old 10-27-2015, 04:54 AM   #6
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Thanks to everyone who has commented so far. Here are some responses.

@Yodaman , checking with the neighbor is a good idea. I did this morning, and they confirmed that they are not experiencing the same symptoms.

@jmon , Unfortunately, I don't have a water pressure guage, but I think I'll be getting one when I replace to PRV this weekend so I can set the new one similarly to our current water pressure.

@Ben , @MTN REMODEL LLC , I agree it's likely the PRV. The existing PRV was installed in 1990 so it makes sense it would be failing now. I see they can be rebuilt, but I'm going to opt to opt to replace this on this weekend. I just watched a video online and it doesn't look too hard. Thanks a lot for the suggestions!

Last edited by bmbouter; 10-27-2015 at 04:56 AM.
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