Leaking cistern flush valve - new

[Hairymary]

Hello, I have got myself into a bit of a mess with a replacement flush valve. Background: The flush handle was broken on my very old concealed low level wc. So feeling adventurous, I decided to replace it with a push button version, so I bought a Fluidmaster Pro550UK cable dual flush valve. I emptied the old tank and installed the new flush valve and button on the front panel where the old handle was etc. It looked good except that I could not get it to flush without leaking. I have a feeling that this valve is not compatible with my 1.5 inch flush pipe. So I am possibly back to square one. Can anyone recommend a suitable flush valve if this is the case?

 

[terryplumb]

where exactly is leak ?
1. valve to cistern
2. flush pipe to valve.
3. flush pipe to pan seal
4.pan seal to pan
????

 

[HERTS P&D]

I'm going for number 2.

Sorry I mean I am suggest it is number 2 and not that I am going for a $h1t.

Andy

 

[terryplumb]

 

[Hairymary]

Yep its No. 2 - Valve to flush pipe...the flush pipe is presently going up inside the valve threaded 'pipe' (but obviously not so far as to interfere with the valve seat). I am reusing the existing locking nut and washer to make the connection onto the valve threaded 'pipe' . I just don't think the flush valve I am using is compatible with a straight connection onto the flush pipe. Any thoughts?
Thanks Mike

 

[terryplumb]

the rubber seal is usually a tapered edge ,ensure the "thinner " edge goes to the valve . also ensure you are not " cross threading" the plastic nut. some have a thin plastic slip ring that goes between the rubber seal and the nut to stop the rubber seal from twisting when tightening up, but not all have this. you should use the nut that came with the valve ,not the old one to ensure thread compatability.

 

[Hairymary]

Thanks Terryplumb,
This morning I took the whole assembly down the local plumbers shop. And with a new tapered rubber washer this time facing the right way, plus the addition of a thin plastic slip ring, it did the trick. Everything you said made sense and is exactly what I did in the end. Now the flush pipe is as dry as a bone in a desert. The valve mysteriously didn't come with a new nut so I used the old one but got away with it.
Thanks again, a satisfying conclusion!
Mike
ps - With the amount of times I attempted to do this properly, I am now quite good at emptying/filling a cistern and removing / installing a flush valve. Cost of job - Materials about £22, Travel - 36 miles with various trips to plumber merchants, Labour about 1.5 days!

 

[terryplumb]

glad your sorted mike ,but don't give up the day job !!