Leak from Isolator valve tap connector nut on bottom fill cistern

[stytagm]

Hi All,

I was trying to replace a failing fill valve in my cistern, I got the old one out no problem, adjusted the new one, popped it in - carefully hand-tightened the nut - and as per the instructions - let the water back in to check the seal. It leaks (sprays) from the bottom of the metal nut that joins onto the plastic threaded cistern valve.

The metal nut at the top of the isolator valve still has some play (relative to the valve) after it's finger tight on the plastic thread. That can't be right surely?

A few questions:
I'm pretty sure I haven't cross threaded it - but how can I be certain?
Do I need to replace the fibre washer? Should the fibre washer push right down inside the nut - or sit just inside it on the threads?

There's a link to a picture - with some arrows to show where the water sprays from. (before you point out that it's wonky - when I took the photo it was just quickly attached to the old fill valve - as I was fiddling about and didn't want to damage the plastic thread on the new valve).

All advice gratefully received.

 

[turnpin]

Welcome to the forums Stytagm clear out any old bits of the old washer and renew...it should sit low down inside the fitting over the shoulder that will fit inside the threaded part of the fill valve and the nut must move freely hope this helps ...regards Turnpin🙂

 

[Magnaman]

Evening mate, whenever changing an inlet valve you should always change the fibre washer as a matter of good practice. The nut should easily tighten on that thread with no loose movement, especially with a new washer and as you've already pointed out, as long as it's not cross threaded it won't leak.

Good luck

 

[ShaunCorbs]

you will know if you have crossed threaded it either see the threads split / bugged or go very tight

either a new fibre washer or rubber o ring should sort you out

(dont forget the retaining cistern nut also) 🙂

 

[stytagm]

Thanks everyone - I'll grab a new fibre washer as soon as the shops open tomorrow. Could anyone eyeball it enough to guess what size washer I want? And is b-and-q OK? I could also get to screwfix or toolstation easily enough.

PS - ShaunCorbs - yes I forgot the retaining nut when I took the photo - I'll remember tomorrow 🙂

 

[SimonG]

Not a fan of them service valves. Also more liable to have issues with plastic to metal. If cross threaded I take my grinder and chop a bit of the plastic off. Not an exact science though.

Best solution is to fit a fill valve with a brass shank. Plenty of paste on the service valve and washer.

 

[Magnaman]

15mm fibre washer matey, b and q, screwfix, toolstation or any good merchant, although no merchants will be open sunday

 

[Magnaman]

Agreed, I install hydroflo valves with the brass shank, however, no paste as it could get lodged inside the valve. If you fit a new fibre washer correctly there should be no need for paste and it won't leak

 

[SimonG]

Brass shank yes, paste yes.

Have to agree to disagree. If you know what you are doing them it shouldn't be an issue. But can see where you are coming from.

 

[Magnaman]

Fair comment Simon, everyone does things different and my attitude is as long as it works/doesn't leak then it doesn't matter how a plumber/engineer does something. If something works by 3 different people doing it 3 different ways then everyone's right

 

[SimonG]

Amen.

 

[stytagm]

Thanks again everyone. OK - One last thing. Is a 15mm washer a 1/2" washer? I can't find any 15mm ones listed on the major DIY/builder's merchant websites.

A link from either Toolstation or Screwfix would be super useful (they open earlier on a Sunday)

 

[SimonG]

1/2" is the one you want. Good luck for the morning 🙂

 

[Magnaman]

Here ya go mate

 

[joni os]

A metal nut on plastic thread is a defect waiting to happen. Trying to tighten on a fibre washer makes failure more certain. This is why fill valves with brass shanks have come back in fashion. If you must use a brass nut make sure you're using one with a soft rubber O ring, so seal can be achieved without over tightening nut on thread.

 

[Harvest Fields]

I always fit ones that have a brass shank. Makes more sense longterm and I have never come across a brass one that has ever leaked where the nut meets the shank. But have repaired lots of plastic ones.

 

[moonlight]

Where is the nut from the underside of the cistern? forget the fibre washer.

 

[gassafe]

I try to line up the plastic shank & the connector finger tight then tighten the valve into the cistern fully otherwise i find it more tricky making it seal!

What's the rubber o-ring people are using?

 

[moonlight]

I try to line up the plastic shank & the connector finger tight then tighten the valve into the cistern fully otherwise i find it more tricky making it seal!

What's the rubber o-ring people are using?

Sometimes there is an o ring instead of a fibre washer but not usually on that type of fitting. We often use mounting compound if it were a brass tail valve. As you have a plastic one. I would suggest you for a new fibre washer and use a small amount of silicone on the washer a tighten up had tight wont be enough. That should do it as long as you have not cross threaded. If you have bin it and buy a valve with a brass tail. No problem tightening up then.

 

[stytagm]

Hi Everyone - I got it fixed on Sunday. 🙂

The trick was that having cleared out the old washer - and in daylight - I could see the shoulder where the two pipes meet on the washer. That showed me that while the new plastic part was the same size - because the big rubber seal/washer inside the cistern was new and thicker than the old - the plastic pipe came short of the brass shoulder in the isolator valve - so wasn't inclined to put any pressure on the washer.

I confess, I gently bent the pipe up a bit to move it a millimeter or two closer to the cistern, and fitted a new o-ring - and it hasn't leaked a drop even done up finger tight. (I did tweak it a little tighter than finger tight in the end).

Thanks again for all the help.

 

[Magnaman]

Well done mate

 

[student plumber]

Had to replace a plastic fill valve with a brass shank one after the plastic shredded the fibre washer.

Brass tap connector to brass shank with a bit of paste on washer and doesn't go inside valve.

Plastic shank only to flexi with rubber washer or plastic nut and its rubber washer and no paste of course, not necessary and rots rubber.

Used to put brass to plastic without second thought before, but since one leaked, plastic to plastic and brass to brass only from then on.

 

[moonlight]

I agree with you totally. I won't fit plastic float valves.

 

[rpm]

Had to replace a plastic fill valve with a brass shank one after the plastic shredded the fibre washer.

Must of been fitted by a gorilla.

 

[student plumber]

Must of been fitted by a gorilla.

That gorilla would have been me.
It wasn't anywhere near tight... So I kept tightening it.
The plastic edge was thin and razor sharp and butchered the washer.