Is a 'water hammer,' always an indication of a problem?

[Phil473]

By water hammer, I mean a slight thumping sound when the upstairs toilet finishes filling.

Have had two plumbers look at it, they both said it wasn't an issue, though the second then gave me a quote to fit an arrester, saying that it may or may not solve the noise.

I'm keen to avoid further plumbing problems later, but the advice I'm getting is a little confusing.

Thoughts much appreciated.

 

[Johntheo5]

What type of filling, is it the traditional ball cock type or something like this Flomasta type, the latter fill at full throttle and then shut off pretty abruptly which may cause water hammer.

 

[Phil473]

What type of filling, is it the traditional ball cock type or something like this Flomasta type, the latter fill at full throttle and then shut off pretty abruptly which may cause water hammer.

View attachment 408804

That's a good point, and I'm surprised neither of the plumbers considered it. I think its the latter, will check when I get home.

If it is the Flomasta type, what would be the solution?

 

[Johntheo5]

Maybe replace it (yourself) with something like this, shouldn't get any water hammer (ballcock type) as it gradually reduces the flowrate as the cistern fills.

 

[Phil473]

Maybe replace it (yourself) with something like this, shouldn't get any water hammer (ballcock type) as it gradually reduces the flowrate as the cistern fills.
View attachment 408812

Interesting...

The downstairs toilet is a ballcock, no water hammer. So you may have hit the nail on the head there.

 

[endecotp]

a slight thumping sound when the upstairs toilet finishes filling.

A "slight thumping" is nothing to worry about.

Bad water hammer sounds like the pipes are about to shake themselves apart, with enough vibration for things to fall off shelves, after waking up everyone within half a mile.

 

[Elsa TLC]

Maybe replace it (yourself) with something like this, shouldn't get any water hammer (ballcock type) as it gradually reduces the flowrate as the cistern fills.
View attachment 408812

Interesting...

The downstairs toilet is a ballcock, no water hammer. So you may have hit the nail on the head there.

You can get water hammer from these valve too.

 

[Madrab]

The type of hammer you are experiencing will be from a loose pipe somewhere. When the fill valve shuts off quickly, it's sending a pressure pulse down the cold pipe and the knock you are hearing is that pulse finding a loose pipe somewhere. Usually on a piece of wood like a joist if it's a low thud.

Probably more of an annoyance than anything to worry about.

 

[Phil473]

A "slight thumping" is nothing to worry about.

Bad water hammer sounds like the pipes are about to shake themselves apart, with enough vibration for things to fall off shelves, after waking up everyone within half a mile.

Pretty much what both plumbers said.

 

[Phil473]

The type of hammer you are experiencing will be from a loose pipe somewhere. When the fill valve shuts off quickly, it's sending a pressure pulse down the cold pipe and the knock you are hearing is that pulse finding a loose pipe somewhere. Usually on a piece of wood like a joist if it's a low thud.

Probably more of an annoyance than anything to worry about.

Actually first noticed it after the installation of a new boiler, and mixing tap.

Not to complicate the issue, but the new mixing tap (kitchen) was producing a slight hammer noise also when switching off. At the time, the downstairs toilet was making a racket while filling, so first plumber changed the downstairs ball cock. That sorted the toilet noise, and the mixing tap noise. Only the upstairs toilet noise remained, which he said was fine.

I'm thinking change the upstairs toilet to ball and cock as suggested by Johntheo5, realtively cheap to do. See if that solves it.

 

[Phil473]

Maybe replace it (yourself) with something like this, shouldn't get any water hammer (ballcock type) as it gradually reduces the flowrate as the cistern fills.
View attachment 408812

Its this this type of flush system/toilet...

Would the Fluidmaster be suitable?

 

[denso13]

Its this this type of flush system/toilet...



Would the Fluidmaster be suitable?

Generally, yes. Just check the space available inside the cistern.

 

[Johntheo5]

Its this this type of flush system/toilet...

View attachment 408920

Would the Fluidmaster be suitable?

Just lift the top off and you should see something like mine, downstairs as well with the Flomasta type filler, if the filling part is offset like mine then should be OK to install the ballcock type, take a snapshot of the inside of the cistern and show it to the plumpers supplier. I installed a 15mm, 1/4 turn ball valve on the supply to mine as its nearest to the water main so the filling is throttled well down.