Replace valve/washer/nut/seal for cistern water inlet leaking where nut meets porcelain?

ClarusDignus

Section62 said:

It is said to be unnecessary, but I would normally put a thick layer of silicone sealant on both faces of the rubber gasket - which will be on the inside of the cistern - so that the sealant does the work of keeping the water in, rather than relying on the pressure between valve/rubber/ceramic to make the seal.

Tightening the nut might work - if you've got a metal tail valve you can get away with more tightening than I'd risk with a plastic one, but bear in mind if the nut is plastic there's only so much force it can take.

If not, I would start again with silicone on both sides of the rubber.  My horse thinks that's the best way.

I checked the two other upstairs toilets. Both of them use sealant too. 

When you say both faces, I understand the bottom face sealant layer will be sandwiched by the cistern surface, but are you saying the top face sealant layer should be sandwiched by the fill valve, where the top of the brass shank meets the plastic, so I'm effectively sealing the gasket onto the fill valve?

I'll acquire sanitary sealant.

I'm not certain if I have the gasket upside down. One face has an inner bevel, which I'm facing down.

I've not tightened the nut with a spanner.

ClarusDignus

NSG666 said:

The new fill valves normally come with a really good sealing washer. Did you tighten the nut with a spanner? If so then you might want to remove the inlet valve and have a really good look at the cistern around the hole looking for signs of it having cracked.

See my last reply for photos of sealing washer.

I've not tightened the nut with a spanner.

Cistern hole from above:



Cistern hole from below:

plumb1_2

Firstly clean. Off the sealant crap from inside and out side of the cistern around the hole, no need for sealant, it will attack the rubber seal
next put the domed rubber washer onto the brassshank, dome facing down
next insert the fill valve
next fit a 1/2” plastic washer underneath not rubber.
next fit the brass nut hand tight
next tighten the brass nut 1/4 to 1/2 turn with a spanner, never over tighten 
next fit a new fibre washer to the tap connector 
next hand tighten tap connector 
next tighten connector 1/4 turn 
next turn on water and check for leaks, if any leak you can gently nip up your nuts 😊
Next adjust the water level 
next putt the kettle on and have a brew.

NSG666

"I've not tightened the nut with a spanner."

It won't seal at hand tight you need to use an adjustable spanner to nip it up - how did you get the old one off? If that was only hand tight then that might be why it was leaking.

I rarely needed to use sealant on any cistern fittings but if you do then you need to use a type that will not attack the washer (as advised above). Despite it's name, sanitary sealant is no good for this purpose. If you are going to use anything then I suggest Stixall.

Section62

plumb1_2 said:

....

next fit the brass nut hand tight
next tighten the brass nut 1/4 to 1/2 turn with a spanner, never over tighten 
....

The OP's backnut is plastic, rather than brass, so is going to need extra care with the tightening, especially as they now have plastic on metal and only one of those is going to win in a contest.

That's one of the reasons why I'd use some sealant and let that do most of the work, rather than hoping a plastic nut will achieve sufficient compression of the rubber to achieve a good seal - and do so without leaving the nut so stressed that sooner or later is cracks and releases the contents of cistern (plus incoming flow) all over the floor.

Personally I wouldn't trust a plastic backnut in this situation...

ClarusDignus

plumb1_2 said:

Firstly clean. Off the sealant crap from inside and out side of the cistern around the hole, no need for sealant, it will attack the rubber seal
next put the domed rubber washer onto the brassshank, dome facing down
next insert the fill valve
next fit a 1/2” plastic washer underneath not rubber.
next fit the brass nut hand tight
next tighten the brass nut 1/4 to 1/2 turn with a spanner, never over tighten 
next fit a new fibre washer to the tap connector 
next hand tighten tap connector 
next tighten connector 1/4 turn 
next turn on water and check for leaks, if any leak you can gently nip up your nuts 😊
Next adjust the water level 
next putt the kettle on and have a brew.

The previously installed valve used a half inch plastic washer. As instructed, I placed it between the underneath of the cistern and the plastic locknut that came with the new valve (no brass nut). I tested this overnight. Vast improvement. No water accumulated on the floor though a very small amount of water (far less than a drop) seeped where locknut and washer meet the underneath of the cistern. I'm repeating this test now but tightening the plastic locknut with a spanner instead of just by hand and will report back in several hours.

I will acquire a new half inch plastic washer and fibre washer.

That's as much of the sealant as I can remove using a plastic rewards card. I think I need to acquire a sealant remover.

NSG666

I don't think you need a new plastic washer and if you look at the fitting that connects to the inlet valve I don't think it has a fibre washer but will be a rubber washer that will be ok.

I don't know why you didn't tighten the plastic nut with a spanner as it was the very first thing you were advised when you first posted.

ClarusDignus

NSG666 said:

"I've not tightened the nut with a spanner."

It won't seal at hand tight you need to use an adjustable spanner to nip it up - how did you get the old one off? If that was only hand tight then that might be why it was leaking.

I rarely needed to use sealant on any cistern fittings but if you do then you need to use a type that will not attack the washer (as advised above). Despite it's name, sanitary sealant is no good for this purpose. If you are going to use anything then I suggest Stixall.

Yes, I've acquired an adjustable spanner. I'm tightening the plastic locknut with a spanner now and will report back.

I removed the old one with a pliers but only because I tried tightening it with a pliers, so I can't say for sure whether or not I originally could have loosened it by hand.

Thanks for recommending a sealant. Can you recommend a sealant remover?

plumb1_2

Use a Stanley knife blade to remove sealant, and go a buy a brass nut.  Toolstation 43258

i never use plastic nuts, I throw them in the bin.
I always have a min of 6 spare brass nuts in my van.

ClarusDignus

NSG666 said:

I don't know why you didn't tighten the plastic nut with a spanner as it was the very first thing you were advised when you first posted.

Reporting back to confirm no seepage since tightening nut with spanner almost 12 hours ago.