new toilet - thump on the plumbing after flushing?

[Webbit]

Hi All,
installed a new toilet with concealed cistern. All has gone well except when it's flushed and refiling the cistern I get a bang/thump from the valve area (and reverberates in the pipework) when it shuts off the water on full refill?

How do I fix?

Also another side issue - my water pressure reads 4bar but the volume of water that comes out of the new sink tap is too great and it ends up splashing over and out of the sink. Any tips on reducing this, I just use it on half turn/pull on leaver but not ideal if there are kids about (eventually!)?

Cheers,
Matt

[wolf1]

I believe it's called water hammer.

Webbit said:

Also another side issue - my water pressure reads 4bar but the volume of water that comes out of the new sink tap is too great and it ends up splashing over and out of the sink. Any tips on reducing this, I just use it on half turn/pull on leaver but not ideal if there are kids about (eventually!)?

Have you got inline isolator valves for the taps? If so turn them down to reduce the pressure.

Edited by wolf1 on Tuesday 2nd August 22:43

[R1 CKY]

You could have a Pressure Reducing Valve installed on your incoming main, this will probably solve the issue with the cistern aswell.

[tim0409]

Hi

is the pipe feeding the cistern well secured? It could be banging against something when the valve closes.

in terms of your tap, you could fit an inline isolation valve and partially close it to reduce flow.

Tim

[Simpo Two]

Webbit said:

installed a new toilet with concealed cistern. All has gone well except when it's flushed and refiling the cistern I get a bang/thump from the valve area (and reverberates in the pipework) when it shuts off the water on full refill?

How do I fix?

Valves can be low or high pressure, you may have the wrong one.

Webbit said:

the volume of water that comes out of the new sink tap is too great and it ends up splashing over and out of the sink. Any tips on reducing this, I just use it on half turn/pull on leaver but not ideal if there are kids about (eventually!)?

On my system (mains cold, gravity hot) I just close the stop valve on the rising main a little.

[Webbit]

Thanks for the replies,

I’m on a combi boiler system so mains pressure water in the bathroom, pipes are secured at 18 inch intervals (where poss) and I have isolation valves on toilet + taps. Tried turning them down but just get more (high pitched) noise on the taps & less water but it does help on the toilet.

I have visited the PRV idea before as I have a separate problem with the dishwasher downstairs causing water hammer on the pipe work, have since secured all pipework every 18in as part of house renovations but currently awaiting a new kitchen with no dishwasher plumbed in at the moment. I have been hesitant to fit the PRV because I don’t want a weak shower, but with these other issues I may need to give it a go.

Does anyone know what the hot water pressure is from a Worcester 28i Junior combi boiler? If less than 4 bar at least I could equalise hot + cold.

Cheers,
Matt

[jagnet]

4 bar is a little on the high side for incoming water. 3 bar is much more suitable whilst still being plenty high enough to give a good shower. It's unlikely you'd notice any difference in the feel of the shower tbh. It will give all your valves and washers (including those inside the combi) a much easier time though, and should stop any squealing and hammering assuming they're all in good condition.

For most combis, anything above 1.5bar will allow it to work at its most effective, so you'll still be well above that. As far as I'm aware there's no pressure reduction valve inside the combi - it'd be flow rather than pressure that gets reduced.

[Ferg]

Was the correct flow restictor fitted in the cistern ballvalve when it was fitted? Failure to do this can often cause the vavle to 'thump' when closing. 'Water hammer' is a continual drone or hum, normally. If it's just a thump then it's the ballvalve's closing action. Modern equilibrium valves are great APART from their susceptibility to high flow rates.