Leaking cistern inlet

[chris0117]

Small leak from water inlet to cistern. Water appears to be coming from the cistern rather than from the coupling I think. See attached photo.

This is a new build just two years old so I am surprised that it can fail so quickly. Does it need a new cistern inlet valve, and, if so is it easy to get one to fit, or just a new washer?

When it is replaced will the metal coupling need any special kind of seal or a new (fibre?) washer?

Thanks in advance for any help.

 

[Old Account]

Small leak from water inlet to cistern. Water appears to be coming from the cistern rather than from the coupling I think. See attached photo.

This is a new build just two years old so I am surprised that it can fail so quickly. Does it need a new cistern inlet valve, and, if so is it easy to get one to fit, or just a new washer?

When it is replaced will the metal coupling need any special kind of seal or a new (fibre?) washer?

Thanks in advance for any help.View attachment 28346

Hi there,

I definitely would change the fibre washer and also too make sure once you tighten the nut to tighten it straight onto the plastic thread as it looks to me not quite right.

Do not overtighten it otherwise the washer will crack.

Just turn the isolation valve off with a flat head screw driver remover the old fibre washer and replace with new one.

Sometimes some people use a little ptfe on the plastic thread.

Kind regards

Ron

 

[joni os]

Quick fix, hold plastic thread with grips to prevent rotation and tighten nylon nut below cistern. This will compress rubber washer that seals hole from inside. Long term, replace fill valve for one with metal tail. Metal nut on nylon thread defies basic engineering, especially when seal depends on hard fibre washer. Be aware that cistern is connected to pan with through bolts and if bolt is allowed to rotate when tightening nylon nuts then internal cone seal will loosen and be another source of leakage.

 

[chris0117]

Quick fix, hold plastic thread with grips to prevent rotation and tighten nylon nut below cistern. This will compress rubber washer that seals hole from inside. Long term, replace fill valve for one with metal tail. Metal nut on nylon thread defies basic engineering, especially when seal depends on hard fibre washer. Be aware that cistern is connected to pan with through bolts and if bolt is allowed to rotate when tightening nylon nuts then internal cone seal will loosen and be another source of leakage.

Thank you. I always worry that if I tighten something it might leak more but I am sure you are right and it might be a temporary fix.

Would the reason for this failing so quickly be poor installation (maybe they used the wrong washer inside the cistern or because the metal and plastic pipes are not aligned properly putting strain on the washer) or do they often not last more than a few years?

Thanks for the information about the connection from cistern to pan. I did not even think about that. So those seals might also fail in the future I guess. Why might they rotate when tightening the inlet plastic collar?

 

[chris0117]

Actually it appears the leak may be from the junction of the metal coupling and plastic pipe. Would the fix be to just replace the fibre washer? What type/size of washer would be required? Does using PTFE tape on the plastic pipe help or not?

 

[joni os]

Regarding rotation of through bolts. It is tightening the nylon nut to left of picture that encourages rotation. Between cistern and pan there is another metal nut and washer that compresses internal rubber cone and provides seal. Clockwise rotation of nut tightens, but clockwise rotation of thread relative to nut has opposite effect.
If leak is at junction of isolation valve and plastic stem then replacement of fill valve for one with metal stem is best long term solution. Replacing fibre washer with soft rubber washer, as in shower hose, might bring short term solution.

 

[rocketmanbkk]

If you change the whole valve get one with a brass shank

Just my opinion

 

[ShaunCorbs]

If you change the whole valve get one with a brass shank

Just my opinion

+1 and the nut onto the fill valve looks cross threaded anyway

 

[rocketmanbkk]

+1 and the nut onto the fill valve looks cross threaded anyway

It does that

 

[JCplumb]

If you change the whole valve get one with a brass shank

Just my opinion

Absolutely this, but don't get the Flomasta one from screwfix, although it appears to be a good valve the shank is shorter than the standard and your pipework looks like it wouldn't move up to adjust for a shorter shank.
The fluidmaster pro has a standard size shank and is the best fill valve out there.
Brass shank = very little chance of cross threading and is stronger than plastic so you can tighten it up enough to seal with the 1/2 inch fibre washer that is usually used in tap connectors, don't try to re-use the one in situ, that never ends well.

 

[john999uk]

Just had the same problem. Well problem was close couple doughnut washer. Then replaced that and fill leaking and overflow leaking (both very bad installations). Went to switch water off and stopcock would not shut off water!
So longer job than expected but after new flush fitted (inbuilt overflow so banked dodgy overflow off), new fill valve (brass thread) and new fibre washer, new washer in stopcock and new gland packing.
After all that no water leaking and we can shut off water in house 🙂 Total cost of parts about £25! But if you are unsure what you are doing get a plumber in. They know how to stop leaks and prevent them by doing the job properly.