Problem with Toilet cistern/filling valve seal

[jauntyangle]

Hello, this is my first post so I hope I'm not breaking any rules by asking for help straight away.

If you want a summary of the below - basically the filling valve hole at the bottom of my cistern is leaking despite trying 2 new and different types of filling valve. I think the hole has somehow widened/warped.


A couple of days ago I noticed water leaking on the floor next to my toilet. I traced the problem to where the bottom of the toilet cistern meets the white plastic nut of the filling valve.

The filling valve was an old-fashioned ballcock type, of which I've replaced before, so I tried tightening the nut, and when that didn't work I took all the steps necessary to refit it (flush the cistern, bail out the water, and sponge the last bits, unscrew everything and refit). It didn't work, so I ordered a replacement ballcock filling valve off Amazon (a Delchem if that means anything).

Unfortunately, the one they supplied had a badly-machined nut which didn't screw up to the top; and various combinations of the old nut/old washer/new washer didn't resolve the problem.

After reading some posts on this forum, I decided to get a Fluidmaster filling valve instead and went to B&Q to get one. Fitting it seemed straightforward; BUT I still had the leak from the cistern. So I now suspect that the hole in the cistern is the problem. I shone a light under the cistern when the Fluidmaster was "fitted" and I could see light above, so I think the hole is too wide. I've tried cleaning it with a toothbrush as there was some debris from the old washer.

So what is the solution to this?

a) Get a bigger washer/adapater for the Fluidmaster (or the old ballcock valve)?
b) Buy some silicone sealant and seal around the washer?
c) Something else?


Thanks for any advice in advance.

 

[cross thread]

Did it not come with a cone shaped washer ? .silicone will also work assuming your cistern isn’t cracked

 

[jauntyangle]

Yes, the washer is on the Fluidmaster thread as per the instructions (cone down). But it's not keeping the leak out, and when I shine a light under the cistern, I can see it from above.

There was a lot of black debris (probably rubber from the old washer), which I've tried to remove with a toothbrush; and I've tried fitting again - actually fitted the old ballcock version and it did seem to be slightly less leaky, but nevertheless still leaked.

There's no cracking in the cistern, but the hole does look like it might be slightly warped; but not so much the washer shouldn't cover it.

Is silicone a permanent solution, or will I end up having this again in a year or so?

I had to take down the boards that were covering the pipes as they were soaked, and don't want to replace them if this can happen again.

 

[Exedon]

Is the fluidmaster the one with a brass thread? It's the only one we use.
Get everything as clean and dry as you can, reassemble with a generous bed of silicone on face of cone shaped washer.
I would add a flat plastic washer between cistern and nut before tightening.

 

[CountryFan]

Is the cistern ceramic or plastic? You could try plumbers mait rather than silicone. Any photos of the problem?

 

[jauntyangle]

Is the fluidmaster the one with a brass thread? It's the only one we use.
Get everything as clean and dry as you can, reassemble with a generous bed of silicone on face of cone shaped washer.
I would add a flat plastic washer between cistern and nut before tightening.

The Fluidmaster model is 400UK073. which is the only one B&Q had in stock - it has a plastic thread.

Bottom Entry Fill Valve - 1/2" Plastic Shank - Fluidmaster

The popular Fluidmaster 400UK fill valve is an ideal replacement for an old-style ballcock. Easy to install, height adjustable and universal fit, it comes with a one-year warranty for peace of mind.

www.fluidmasteruk.com

If I use silicone on the washer, do I let it dry before reinserting it into the cistern (the purpose being to give the washer a bigger surface area) or is the purpose to have the wet silicone set it in place.

If it's the latter, I'm concerned that if the leak persists despite the application, it will damage/make useless the valve/washer and I'll be back to square one.

Is the cistern ceramic or plastic? You could try plumbers mait rather than silicone. Any photos of the problem?

The cistern is ceramic. It's hard to get a photo, as it just a hole at the bottom of the cistern. I think the problem is that the hole has been warped slightly (possibly by the previous valve being overtightened and pressed against it); and so the washers don't quite seal it. There was a lot of black debris around the hole - probably the rubber from the old washer, and it looked like there were some unnatural grooves in it.

The other possibility is that I've just been VERY unlucky with 3 different washers from 3 different valves. Would a bigger/wider washer be a solution?

I'll have to go to Screwfix (not B&Q as the staff were unhelpful/unknowledgeable, and it was a bit of a trek); to pick up supplies. Is there any specific products/brands I should be asking for?

 

[CountryFan]

The cistern is ceramic.

I think the problem is that the hole has been warped slightly (possibly by the previous valve being overtightened and pressed against it);

I doubt this on ceramic

and so the washers don't quite seal it. There was a lot of black debris around the hole - probably the rubber from the old washer, and it looked like there were some unnatural grooves in it.

Might just be not a clean enough seating.

Would a bigger/wider washer be a solution?

@Exedon suggested a plastic washer as extra, maybe try this. Screwfix are part of same group as B&Q - you'd be better off in a plumbers merchant.