PEX noise question

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oldpops

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Hi all! I'm an old retired guy on a very limited income so I have to fix things myself. Anyway, we are living in a house with a PEX plumbing system here in southern California and recently every-time someone flushed the toilet, we could hear a faint 'knocking' or 'pulsing' or 'pumping' sound. We have been here over 9 years and never heard the sound until the last few months. In the last few days the sound has gotten 'louder', and it now appears to be happening even when the washer machine goes on. I have read a few posts about air hammer even in a PEX system, and I know that somewhere there is a 'manifold' that distributes the water to all the faucets, sinks and toilets, but I have not been able to locate it. I am thinking the Manifold is hidden somewhere in the attack because it is easy to tell it is no-where in the garage. Don't see any obvious leaks anywhere but since the sound is louder and more pronounced now I hope it isn't getting worse? Can anyone offer any advice on what to check and/or look for? And what to do about it.

Thanks in advance to all who offer help and advice!
 
Generally, noise in PEX is caused by the PEX not being secured within the wall cavity.

However when the symptoms follow or are associated with a particular appliance or fixture usage the fault may lie there, so the fill valve on the toilet may be reaching it's life expectancy, and are not expensive to repair.
 
City water?
First thing I'd be checking is the incoming water pressure.
A simple gauge like this, connected to an outside faucet will be all you need.
https://www.homedepot.com/p/Watts-3-4-in-Plastic-Water-Pressure-Test-Gauge-DP-IWTG/100175467
If it was just one thing that was acting up I'd agree with the fill valve acting up, more than one you start looking at the common denominator.
The water pressure does not need to be over 60 PSI max.
Higher than that the PRV (pressure relief valve) may be bad.
Both the manifold (if there is one) and the PRV should be located close to where the incoming water comes into the home.
 
The sound doesn't happen when the rear bathroom is flushed, or when any of the faucets are opened/closed. So far i have only heard it when the front bathroom toilet is flushed so i was thinking the toilet in there is the source of the problem (it has one of those eco-friendly water usage reducing hook-ups in the tank). However, my kids tell me that the sound also happens now when the clothes washer is used. We are on city water, but if anything our water pressure is a joke. It takes forever just to fill a pot of water to cook. I know the manifold must be somewhere in the attic but I have not been able to locate it. I will have to look again. Once I find the manifold, is there anything I should be checking for? And what is, and where is the pressure relief valve you are referring to?
 
There's no reason there has to be a manifold, you may just not have one.
I'd still check the incoming pressure, if it's OK then likely someone has ran undersized main runs causing the low flow.
A 3/4" line will have about twice the flow of a 1/2" line, low flow, low pressure once a lines been opened up.
Picture standing on a garden hose and open up the nozzle, at first full pressure then it drops off.
As already stated the pressure valve will be some place on the main incoming water line before anything else.
 
If there is a pressure regulator it will be at the main shut-off just below the hose bib at the front of the house.

There will be an aerator on the kitchen sink faucet the can be clogged and can be easily removed and the flow checked, and then cleaned if the flow improves.
 
The two things you should be looking at are the valve for the toilet or the fill valve in the toilet. The supply valve has a washer that isn't always secured the best and the fill valve in a Mansfield toilet or a korky fill valve can just be old.
 
Do you get the, "faint 'knocking' or 'pulsing' or 'pumping' sound" while the washing machine is filling or just momentarily, when it starts filling?
Just thinking, based on the description of the sound, that maybe it's a loose washer in a valve(if you have any globe valves) or a sloppy gate valve.
You mentioned the toilet and the washing machine. So it doesn't happen, in the front bathroom, when using the sink cold water faucet? Even when opening or closing it rather quickly?
 
Well, from what I can tell, the faint knocking, or pumping sound is coming from the attic. And the sound goes on for about a minute or so after flushing the toilets in either bathroom/front or back. It also makes the noise when the clothes washer is filling. So I think the problem is not related to a single fixture. I don't have a water pressure gauge but we sure don't have any more pressure than we have for the last 9+ years. It looks like a 3/4 inch pipe coming into the house from the street if that means anything. Unfortunately due to age and some health issues I can't get into the attic. However, I can ask my son to go up there when he comes over but I need to know what to tell him to look for.
 
When he is in the attic, flush the WC and have him strap the pipe that is vibrating against the wood, to secure it.
 
Thanks. My son hasn't been over yet to go up in the attic yet but in the meantime I have noticed that we get the knocking/pumping sound whenever any toilet or shower in the house is used, along with whenever the clothes washer is used. So, because of the fact that any large use fixture causes the noise, I don't think the problem is related to a single pipe or pex line is causing the trouble. Of course maybe one pipe is causing the others to vibrate.** Oh, and I went outside to take out the trash and walked past the water inlet pipe to the house. I could hear the slight tapping/knocking/pumping sound by the inlet pipe? Does this give a better idea of what's going on?
 
You generally do not experience telescoping with pex, but since you here it at the main, close that valve slightly and see if that changes anything.
 
As @Snoonyb says, "...close that valve slightly and see if that changes anything."
While the the noise is taking place!
May want to try it on other main valves, as well.
 
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