New case of water hammer when we flush the toilet

[Canada_DIY_Plumber]

When we flush our toilet, we are hearing loud water hammer somewhere in the walls that goes on for a good 5-10 seconds. I have confirmed it is when waster is supplied to the toilet and not a venting noise by turning off the water supply valve and then flushing, and then turning the supply back on. The noise is directly correlated with water running in the supply line.

When I run water in the kitchen sink and then flush the toilet, I don't experience this noise.

About a month ago, we added a thermal expansion tank near the hot water tank (we previously didn't have one) but the sound just showed up today.

Any ideas? Perhaps my old hammer arrestors on the washing machine have gone bad (they are close to the toilet.) I've never seen a hammer arrestor installed on a toilet supply line but is that an option I should consider?

 

[Plumber69]

probably the valve feeding toilet. Try having that valve 1/2 way open

 

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[Jeff H Young]

Water hammer problems can be hard to diagnose , My opinion is the "problem " is almost never a bad hammer arrestor. A toilet shouldn't need one. but adding one could fix it, as could , replacing the fill valve .
I don't think I've ever repaired a hammer by replacing the arrestor. but you gotta be willing to try a lot of things it can be frustrating to solve

 

[Reach4]

Water hammer is a single bang when the flow stops. I think a different term, such as flutter, machinegunning, chatter, vibration, might apply.

Let us know how that adjusting your stop valve works out.

 

[Terry]

5-10 seconds sounds like a bad shutoff at the wall. The loose rubber washer flutters while filling. Sometimes you can open the valve all the way and that helps. If not, replace it.

 

[Canada_DIY_Plumber]

Thanks all. I'll see if fooling around with the valve helps and if not, I will look at replacing it.

 

[WorthFlorida]

As Terry suggest a bad seat washer on the shut off valve can cause it, also a cause is the Fill valve inside the tank. Depending on the type of Fill valve, if you have a Fluidmaster, replace the valve seal. If it's an old ball cock, replace the entire fill valve with something new.

https://www.homedepot.com/p/Fluidma...Valve-Seal-for-400A-Fill-Valves-242/100580550

 

[Canada_DIY_Plumber]

Mystery solved: My wife had used the hose recently and didn't completely close the valve. The noise appears to have been originating at the anti-siphon valve at the hose bib and then reverberating throughout the house. I think the solution is to just turn off the tap at the hose bib when we aren't using the hose.

 

[Reach4]

Mystery solved: My wife had used the hose recently and didn't completely close the valve. The noise appears to have been originating at the anti-siphon valve at the hose bib and then reverberating throughout the house. I think the solution is to just turn off the tap at the hose bib when we aren't using the hose.

Now that is a weird one.

 

[Jeff H Young]

Mystery solved: My wife had used the hose recently and didn't completely close the valve. The noise appears to have been originating at the anti-siphon valve at the hose bib and then reverberating throughout the house. I think the solution is to just turn off the tap at the hose bib when we aren't using the hose.

easy fix.