Stumped re water hammer issue

[Stumped789]

We have a 1940's house with a 20 year old upstairs addition. We have never had water hammer before until recently. Work done recently which could correspond with the timing of water hammer are new water heater and new flooring which involved disconnecting and reconnecting appliances.

Water hammer happens both upstairs and downstairs including at showers and faucets unless we turn off the water very very slowly. We have copper pipes. At times, I've even heard the pipes rattle in the middle of night when no water is flowing, tho this is uncommon. The main issue is when water is being turned off. That's when we hear a distinct thud.

We have had several plumbers come out. Pipes do not appear to be loose. One plumber changed the fill valve on a toilet and two faucets and those hammers disappeared. But hammers in the rest of the house remain.

Just totally stumped as to what could have caused this after living in this house for 20 years.

P.S. We have tried turning water off to "reset" air chambers.

Thank you for any input!

 

[Reach4]

You are looking at the right things.

P.S. We have tried turning water off to "reset" air chambers.

How long did you leave the water at zero pressure? You might try a longer time, such as overnight.

So what has changed? I would measure the water pressure, to see if that has gone too high. You can get a garden hose thread pressure gauge for under $20, and often under $10. This can connect at a laundry tap, outside spigot, or the drain on the WH.

 

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[Stumped789]

Thank you. We left the water off for probably 15 minutes, until the dripping stopped from all the faucets. Could leaving it off longer really make a difference?

We have a pressure regulator but it's old. The last time the plumber checked it was at 70 psi. Could psi fluctuate? Because I notice he just did a quick reading at the laundry tap for a split second.

 

[Reach4]

Could leaving it off longer really make a difference?

That is a concern that is often voiced-- that they don't drain out well. Seems worth a try, if you are going to be a way for a period.

We have a pressure regulator but it's old. The last time the plumber checked it was at 70 psi. Could psi fluctuate?

PRVs can go bad, and need to be rebuilt or replaced. A pressure gauge is cheap and easy.

If it is working, consider turning down the pressure to maybe 45. Always run a faucet a bit while adjusting so that you can see the effect of your adjustment.

 

[Stumped789]

Thank you so much, I will try those things.

 

[Fitter30]

With water off open all the valves and leave valves open as long as you can. When turning water back on just fill slowly before turning water all the way on. Their are air chambers at most devices for water hammer that could be full of water instead of air.

 

[WorthFlorida]

When you turn off the water to refill any air chambers, you need to drain the entire system. At the lowest point a spigot or faucet needs to be opened and everything else opened to allow air in. If you are without a basement, usually the outside spigots are the lowest point. While you do this close the cold water valve to the water heater and shut it off, gas or electric. Then do what fitter 30 recommends.

 

[Jadnashua]

An air column versus a hammer arrestor are two different things. An air column is sort of like what happens when you put your finger over the end of a straw...the water doesn't come out easily, if at all, since there's no way to break the suction so the water can drain out when you shut the water off. Over time, any air that you can get in there will be absorbed as the water passes by, and that water will gradually fill the air column, negating any functionality. If you need hammer arrestors, do not install an air column, as your work will eventually fail to perform its intended function. Unfortunately, a hammer arrestor won't last forever, either, but much longer than an air column.

A hammer arrester is an engineered device that works until it fails. It will have either a bellows, or a piston in it with air trapped. Either the moving water column compresses the bellows/bladder, or moves the piston, compressing the air, then when the pressure from the water goes back down, returns to the static position.

If any other work was done, the utility may have installed a check valve. But, with a PRV, you have what is called a closed system. If you have an expansion tank, it may have failed. If you don't, you need to add one. The new WH, coupled with new toilet fill valves, may have tightened up the system enough so that it doesn't leak to relieve thermal expansion, that can create noises as the water pressure rises.

Is the T&P valve on the new WH opening?

 

[James Henry]

Funny thing happened to me recently. I started getting water hammer at every fixture in the house, turns out I left the garden hose on and the hose bib vacuum breaker was causing the shock.

 

[Jeff H Young]

70 psi is high plus you should verify that it only goes that high. my toilets were doing same thing and fill valve change out caused more gentle turning off.
My opinion has changed over years they say 60 is good but I prefer lower less problems. prvs are preset at 45 and I leave them there.
Draining water down yea that can help . sometimes trying anything is a good idea and what could be easier.
If you are paying plumbers then I think Id invest in a pressure gage. This can get time consuming as its just not real obvious the problem

 

[Terry H]

70 psi is high plus you should verify that it only goes that high. my toilets were doing same thing and fill valve change out caused more gentle turning off.
My opinion has changed over years they say 60 is good but I prefer lower less problems. prvs are preset at 45 and I leave them there.
Draining water down yea that can help . sometimes trying anything is a good idea and what could be easier.
If you are paying plumbers then I think Id invest in a pressure gage. This can get time consuming as its just not real obvious the problem

prvs come set at 55. I wouldn’t consider 70 high. Over 80 I’d say is high. I like mine around 65-70. Fixtures and things start having problems above 80.

You may use different prvs but 45 is low.

 

[Jeff H Young]

Terry H water hammer issues are worse with higher pressure. If someone told me it was 70 Id consider lowering and get a gage to verify. any ideas ?
Stumped 789 Is your house part old galvie and 20 year old copper, pex , or cpvc? when running water does it come out fast and then slow down after a short time?

 

[Terry H]

Terry H water hammer issues are worse with higher pressure. If someone told me it was 70 Id consider lowering and get a gage to verify. any ideas ?
Stumped 789 Is your house part old galvie and 20 year old copper, pex , or cpvc? when running water does it come out fast and then slow down after a short time?

no doubt higher pressure will make it worse. I was just hung up on the pressure that seemed low but it depends on volume etc pressure is not everything but it does tell a lot.

anyhow, I wish I had some insight on this but short of coming and looking at it I’m drawing a blank.

 

[Terry]

Do you have an icemaker in the refrigerator? The ice cube trays refilling all night long will cause the pipes to hammer unless you install a hammer arrestor on the shutoff.

Sometimes old plumbing fixtures like a slow leak at a toilet prevent the hammering you would get on a tight system. We often hear of water hammer being worse after slow leaks have been stopped.

UPC likes hammer arrestors for the dishwasher, ice maker and washer.

 

[Jeff H Young]

Its a nerve racking thing. stumped 789 where you at on this now? One thing Ill say is weve all encountered and battled water hammers . Some guys are big on water hammer arrestors. Im not but I like anything that works though. And have put them on to aleviate with some sucess.
I think old galvie pipe either undersized or long runs . along with newer pipe pipe that is full diameter can cause a hammer. Does hammer happen near the water service PRV or further away down the line?

 

[Jadnashua]

Force is equal to the mass * velocity squared...so, the higher the pressure, the faster it goes, the more force it can generate. Momentum gets messy with right angles, since the force wants to keep things going straight. That can make a pipe literally jump and hit things. So, you need to slow the impact, and that's what hammer arresters are designed to do. They need to be as close to the thing that tried to stop the flow, typically, a fast operating valve (ice makers, washing machines, some toilet valve, etc.). Most valves don't close fast enough to create a problem, but on any that do, especially if your pressure is higher, may need a hammer arrester. An air column, the old way to do this, usually fills with water fairly quickly, and fails to continue to function until it is drained. An engineered one has a sealed air chamber, so water never touches it. There's a big difference in longevity between an air column and a hammer arrester. So, the thing needs to be close to the errant valve, and you need to get your water pressure in check. Plumbing code calls for it to be NGT 80-psi.

 

[Stumped789]

Thank you so much for all the input! I really appreciate them.

We had our plumber out 2 days ago. He re-checked the pressure at the water heater (last time he checked at the laundry). This time it was at 75 (it was 70 at the laundry). I asked him if we should turn down the pressure, and he said no. He said anything under 80 was fine.

He strapped down the pipes under the kitchen sink. They were a bit loose. I'm not sure if that made a difference. I'm going to observe all the noises and possibly get a second opinion from another plumber. I especially want to ask about the water pressure, as some of you thought 70 was high.

I plan to re-drain the pipes as a couple of you have suggested. I just need to find a window of time when the kids will not be needing to use the water. I have teenagers who are going to bed around 3am these days, so it's hard to wait up to drain the system overnight.

My plumber says this is a tricky situation. It will just be a process of elimination at this point. He is also not a fan of water hammer arrestors.

I neglected to mention we have very hard water. I've since put in a whole house no-salt softening system, but for several years before that, we had very hard water in the house. Could this have caused the hammering?

Thank you all again.

 

[Reach4]

I especially want to ask about the water pressure, as some of you thought 70 was high.

I did not think 70 was too high per se. I was thinking it is easy to adjust a PRV down to see if that makes the water hammer less. For most household stuff, I don't think you would notice the difference. For lawn watering, you might.

 

[Stumped789]

I did not think 70 was too high per se. I was thinking it is easy to adjust a PRV down to see if that makes the water hammer less. For most household stuff, I don't think you would notice the difference. For lawn watering, you might.

Sorry I misunderstood. Anyway, it would be one of the questions to ask of another plumber when he's here.

 

[Jadnashua]

Most valves like a shower one, are flow rated at 60-psi as a reference. Devices are rated for normal pressure NGT 80-psi. They're tested to higher values to have a margin of error and protection. For example, your WH, when new, was tested to 300-psi, but the safety valve is designed to open at 150 to give a margin of error. Hoses to things like faucets, washing machines, etc., tend to fail sooner when the pressure is higher, and the spikes from a water hammer will wear them out, too, sometimes, catastrophically.

A water column will saturate, sometimes within a month or two depending on the application. A hammer arrestor can last decades. Draining the water may not purge the water in the air column.