Leaking Cistern

[Makeitgo]

Hi All

I’ve got an old lever type, dual flush, Dudley cistern and there is a leak around the flush valve back nut. My guess was a problem with the seal washer that goes between the cistern and the base of the flush valve, so took a look at it and it didn’t look too bad, but I still swapped in a new one from another new flush valve anyway. FYI, I intend to keep the original flush valve as it’s the correct threaded pipe length for the existing flexi flush pipe, long story...

I checked the lip in the cistern (seating surface for the washer) was free of scale, damage free and flat/smooth and it was. I reassembled the valve with the new seal washer – nut done up “enough”, but still it had a leak. I tried tightening it more and the leak was still present.

I got advice from the well stocked local shop and I bought a replacement seal washer (albeit a bit larger diameter) of the same thickness, an additional seal for the nut side (their idea to help seal) and a poly-washer for the nut to slip round.

Put it all together again, repeated the same testing and still a leak. Again, I tried tightening a bit more but still no luck. I’ve really had a gut-full of this as we’re selling and I know the new occupant will rip the old toilet out and replace it. Just want it leak free to show the property.

Just wondering if anyone had any advice? I not not a big fan of botches, but has anyone resorted to using a sealant on the cistern seal lip and washers etc? If it was to happen, I’m looking at Fernox LS-X or some constant exposure to water type silicone sealant if that's not counter productive.

Pics attached, cheers.

 

[Wayners]

Normally ¼ turn past hand tight and all good. There is no water pressure.
Rubber ring on inside of cistern. Just a gentle tighten. Don't dog up tight crushing rubber. Maybe you are overtightening it?

 

[Makeitgo]

Normally ¼ turn past hand tight and all good. There is no water pressure.
Rubber ring on inside of cistern. Just a gentle tighten. Don't dog up tight crushing rubber. Maybe you are overtightening it?

Cheers Wayners. I'll go back to the single rubber washer and give it less spanner then. I've never had as much trouble with stuff like this before, so can't work it out... I'll give it a go.

 

[Madrab]

Look like plastic? TD's tend to be.

If you've tried everything, new seal etc and it's still leaking then last resort would be a little silicone on all the mating surfaces. If it is plastic and after that it still leaks then then there could be a hairline crack on the cistern or the spigot of the flush valve from all the years of pulling on the handle and the flexing it can produce.

 

[Makeitgo]

Cheers Madrab. I'll have another close look at it all. Hope it's not the cistern, this one's only about 10 years old and exactly the same as the old one (then made by Shires) and that was about 20 years old when it bit the dust.

 

[Makeitgo]

Hi All, thanks again for your help. I thought I’d just do an update about resolving this as I’ve just saved myself £120 odd quid for a new cistern.

I eventually took the Cistern off and found there was a crack I just couldn’t see while it was still screwed to the wall. It was the tiniest crack ever and considering there is next to no water pressure on the outlet seal I was surprised to see how much of a seep this critter was causing. Anyway, the leak was right at the base of the ring that forms the seal seat and was visible from underneath the cistern where the lock nut’s poly-washer sits. You can hardly see the crack but there was also a microscopic residue of lime scale in the crack’s area which added to the evidence.

So, I roughed up the area of the crack inside and outside (bottom) of the Cistern and sealed these areas with epoxy. I heated the epoxy up while it was going off with the heat gun on the underside with a view for it to run into the crack (although it might not have) but all went well.

I left it overnight, put it all back together and it’s been totally watertight since. What would we do without epoxy huh? Photos attached.