Cistern making clunking noise

[cam123]

Hi all,

I've just had a concealed cistern lav fitted downstairs, and to my dismay it makes a loud clunk-clunk-clunk-clunk noise at the point at which the valve is just closing off (i think, as it happens after the cistern has been filling normally for a while).

Builder says it because of some stiff part in the cistern/will be ok once flushed for a couple of years! But this sounds a bit odd to me.

The basin in this cloakroom also has a very noisy tap, so i'm wondering if this could maybe be a related cold water pressure problem perhaps?

Any thoughts would be much appreciated! Thanks.

 

[delongie]

Hey if u getting noises from yr cold water tap as well,i would check yr pressure for sure.. u may need to try a pressure reducer on yr cold water pipe just under the tap if the pressure is too high

 

[Roadyz]

sounds like water hammer.

 

[cam123]

we've now reduced the cold water flow at the isolation valve under the basin which has helped a lot. I'm more worried about the lav though and how i get rid of the clunking noise.

With regard to reducing the mains pressure, sorry if this is a stupid question, but is it not possible to do this by half closing the main stop cock? or do i have to fit an entirely separate valve onto the pipe?

What is water hammer and how do i get rid of it?!

Many thanks.

 

[seco services]

sometimes reducing the mains stopcock can ease certain noises etc.
but you won't reduce the pressure only the flow, what is what you don't want.
to reduce pressure you'll need a prv.

is the noise on the tap all the time its running or when you shut the tap off ?

 

[cam123]

the noise was only when the water was flowing through the tap and was a loud and constant gravely noise. Dodgy builder started talking about change in pipe diameter/round to rectangular spout etc etc... basically blaming the tap, but to me it just seems that too much water was trying to get out in too short a time.

The flow from the tap is obviously now limited and all is well.

With the lav though, if we are assuming that this is a high pressure and hence water hammer problem, is it not possible to solve this in the same way i.e. by reducing the water flow through the isolation valve on the pipe to the lav? Thus avoiding having to fit the prv?

Also, how would a prv affect the upstairs bathroom (that doesn't have pressure issues ) shower etc. if we were to fit one?

 

[seco services]

try the iso valve first, may improve it.

its not water hammer that happens when you shut a tap or water changes direction.

can't you fit a prv to the pipe that supplies the basin and wc only.
say in the cloackroom.

if the noise is like air in the pipes. i find sometimes the cheap iso valves that have a restricted bore can cause alot of noise compaired to the full bore iso's

 

[TheMrX]

With the lav though, if we are assuming that this is a high pressure and hence water hammer problem, is it not possible to solve this in the same way i.e. by reducing the water flow through the isolation valve on the pipe to the lav? Thus avoiding having to fit the prv?

Give it a try and find out. The worst that can happen is that your cistern is a bit slower to fill up.

 

[Gas2Air]

"Dodgy builder started talking about change in pipe diameter/round to rectangular spout etc etc..."

Sure that wasn't you trying to keep her indoors quiet?

 

[cam123]

lol!

'fraid not. what with being a wee woman myself

 

[cam123]

After researching water hammer on tinternet, i decided to check if it was a water hammer problem in the lav by draining the system and purposefully leaving an airlock (which i read would work as a dampener to the shock waves through the water and pipe). Sure enough, once i'd done this, the first five flushes of loo were fine with no clunking.

Sooooo, i'm thinking that i'll try to reduce the flow through the iso valve and if that doesn't work too well, i'll fit a water hammer arrestor? Or as we said, i could fit a prv just into the cloakroom. I'm not sure which of these would be the better option though?

I'll keep the iso bore issue in mind for my en-suite starting today - thanks.