Noisy cistern.

scooby1 · 31 Jan 2020

I wonder if anyone can help please ? One of our toilet cisterns has developed a "clunking" noise when the re-filling process finishes. It does it on both the long and short flush. It's about 9 years old. I know my way around ball valves but this is all new to me. Can anyone tell me why it is making this noise please and if it's possible to get rid of it ? The chrome thing is what screws through the top and into the mechanism when it's in position but thought I would show it. If I had to guess I would have to say that the noise is coming from the bit on the left. Is that the shut-off valve ?

Thanks in advance for any help given.

jackthom · 31 Jan 2020

Is this a bang that goes through the water pipes? Most likely when full the valve is cutting off the water very rapidly which results in "water hammer".

If you've never had this problem before anywhere in the house then replacing the whole inlet/float valve assembly on the left of the picture should sort it out.

terryplumb · 31 Jan 2020

The valve on the left is the float valve,
(Filling valve) and controls the flow of water into the cistern. Flush the WC and watch the water level rise in the cistern ,if the" clunk" sound happens just as the water gets to its highest position ( when the float valve closes),then it's a problem with the float valve. However ,if the sound happens just after flushing ,and when water level is very low in the cistern ,it's the flush valve ( the centre of the cistern )

scooby1 · 31 Jan 2020

jackthom said:
Is this a bang that goes through the water pipes? Most likely when full the valve is cutting off the water very rapidly which results in "water hammer".

If you've never had this problem before anywhere in the house then replacing the whole inlet/float valve assembly on the left of the picture should sort it out.

Thank you for that. No, never had it before in this type of situation but we had it shortly after finishing the house build about 9 years ago when we turned a kitchen tap off. Our plumber put a device in the line that I think took some of the "sting" out of suddenly turning the tap off. I probably should have mentioned that we are on an un-vented pressurised water system (I hope that's the correct terminology) Anyway, we don't have a header tank, we use the mains pressure to get the water everywhere.

scooby1 · 31 Jan 2020

terryplumb said:
The valve on the left is the float valve,
(Filling valve) and controls the flow of water into the cistern. Flush the WC and watch the water level rise in the cistern ,if the" clunk" sound happens just as the water gets to its highest position ( when the float valve closes),then it's a problem with the float valve. However ,if the sound happens just after flushing ,and when water level is very low in the cistern ,it's the flush valve ( the centre of the cistern )

Thank you for that. Yes, the clunk sound happens just as the water stops coming into the cistern (when the water level is just at the top of the float valve) . Can I take the float valve out out and dismantle it and fix something in there or is it a complete new set of innards for the cistern ?

just pumps · 31 Jan 2020

The thing the plumber fitted was probably a Shock Arrester.
Can you feel the pipe judder when the noise happens.
Can replace the whole valve for a high pressure one or fit the arrester

terryplumb · 31 Jan 2020

Just fit a new float valve

scooby1 · 31 Jan 2020

just pumps said:
The thing the plumber fitted was probably a Shock Arrester.
Can you feel the pipe judder when the noise happens.
Can replace the whole valve for a high pressure one or fit the arrester

Thank you for that. It is one of those loos where you can't see any pipework to fit an arrester. It was installed when the house was built around 9 years ago but what I don't understand is why it has only just started to make the noise. I don't think the mains pressure has increased. We are out in the sticks and we do experience pressure reductions sometimes (when everyone is having a shower or watering the garden !) so I'll flush it when I think the pressure has dropped.

scooby1 · 31 Jan 2020

terryplumb said:
Just fit a new float valve

Thank you for that. I suppose I will have to take the old one out to find out what sort it is. Another thing I don't understand is why did I find a small piece of mortar (I think) in the bottom of the cistern and there appears to be 2 holes at the bottom which can just be seen and it looks as if they have mortar or something like that over them.

terryplumb · 31 Jan 2020

You don't have to replace the float valve with an identical make /model. A fluid master bottom entry float valve with brass shank would be my choice.
Beneath The two round blobs are the bolts that hold the cistern to the pan ,and are encrusted with rust/ limescale and possibly putty or silicone . It would be wise to have replacements at hand ,if the cistern has to be removed from the pan. Some float valves can be replaced without seperating cistern and pan. If you can see / reach the nut below the float valve ,and the supply pipework to it ,you won't need to move the cistern.

just pumps · 31 Jan 2020

It's most likely happening now due to fair wear and tear so to speak in the valve.
Most plumbers like the Fluidmaster valves however I don't use them for low pressure systems.
Remember to postion the valve where the float doesn't touch the cistern insides.

scooby1 · 31 Jan 2020

terryplumb said:
You don't have to replace the float valve with an identical make /model. A fluid master bottom entry float valve with brass shank would be my choice.
Beneath The two round blobs are the bolts that hold the cistern to the pan ,and are encrusted with rust/ limescale and possibly putty or silicone . It would be wise to have replacements at hand ,if the cistern has to be removed from the pan. Some float valves can be replaced without seperating cistern and pan. If you can see / reach the nut below the float valve ,and the supply pipework to it ,you won't need to move the cistern.

Thank you for that. I'll have a look to see if I can detect a nut under the float valve but you have been very helpful today. It's good to know what the rust/limescale is and what it's covering. Thank you very much.

scooby1 · 31 Jan 2020

just pumps said:
It's most likely happening now due to fair wear and tear so to speak in the valve.
Most plumbers like the Fluidmaster valves however I don't use them for low pressure systems.
Remember to postion the valve where the float doesn't touch the cistern insides.

Thank you for that. Is that a Fluidmaster valve in there then ? I have Googled & YouTube'd that and plenty of stuff on the 'net about them. I thought it might be wear and tear, it's the downstairs loo and gets used more than any other. Thank you for reminding me about the float not touching the sides. Thanks again, you've been very helpful.

CBW · 31 Jan 2020

scooby1 said:
Thank you for that. Is that a Fluidmaster valve in there then ?

No, that’s a Siamp along with a Siamp flush valve. If you can’t get to the inlet valve, then you may be able to unscrew the existing top half out and replace the top half, or undo a locking nut (grey in colour) and pull up to separate and insert new one and secure with locking nut.

just pumps · 31 Jan 2020

Siamp are decent valves.

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Noisy cistern.

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