Can anyone advise on a cistern that has a slow drip please?
I've only just replaced the whole cistern unit. The drip comes through
the thread of the pipe sticking out of the bottom (actually it's all
one piece with the internal mechanism. It was also leaking directly
under the cistern untill I put some evo-stick on there - so its a bit
A previous post recomended Fernox Leak Sealant - is this the right
stuff? The evo-stick was recomended by my local plumbers merchant. I
also have some PVC glue.
(By the way the unit also had a leak at the join with the inlet pipe,
due to nut not threading properly. I managed to cure this by cutting
the pipe down a bit to remove a section with wonky thread, but is all
this kind of thing a common problem wth plastic joints?)
Anyhow thanks for any help,
Like the man says you probably have a leak where the cut end of the threaded
section tries to join to the connector on the pipework feeding it.
Cross-threading and thus mangling the threads is a hazard with plastic inlet
valves: the trick is to leave the valve screwed only loosely into the
cistern until you've screwed the connector nut a few turns onto the thread
by hand so you know it's on straight. What you might do if you have
sufficient length of pipework feeding the cistern valve is cut it and use a
Speedfit tap connector like
which has a rubber rather than fibre sealing washer (which may take up the
irregularities in the cut end of your thread) and can (and must) be entirely
tightened by hand (so you don't ruin the thread on the valve again). You
could put a service valve (like
http://www.screwfix.com/app/sfd/sea/searchresults.jsp?n 483 or
http://www.screwfix.com/app/sfd/sea/searchresults.jsp?n 372) in the pipe
while you're at it.
Thanks Alex & John. But, Erm, the pipe I cut back a bit (water inlet)
cured the leak on that one. The one i didn't cut (underneath, delivers
flush to pan) is the one with the leak. This leaky one just has a has
a plastic screw ring that you're supposed to tighten to make
water-tight - only it ain't.
Suppose i'll try some of the sealers in my 1st post, & if doesn't work
take the cistern back to Plumb centre for another.
Did you place the large rubber washer inside or outside the cistern,if out
it should be in..Failure to tighten the backnut correctley often cuases
leaks at this joint.A smear of silicone between washer and syphon and washer
and cistern should solve your problem.Cleanliness and drying the area is
also very important.
I change these at least 5 or 6 times a month fitted correctley they do not
Most plastic fittings recommend you don't use any form of additional sealant
on the joints; some sealants will attack and weaken the plastic.
If the cistern is leaking from the bottom, check the rubber washer (normally
fitted inside, not outside), also the nut shouldn't be too tight, if it is,
it can crack the plastic; it needs to be just tight enough to seal; if it
requires anything more than hand-tight, there's something wrong.
I may well get flamed for this, but, I often use a (very) small amount of
Vaseline on plastic fittings where there is a compressed rubber washer, it
helps with sealing and also makes it easier to remove should you have to in
John, yes it does have a washer. Maybe part of the problem is that the
whole internal mechanism leans a bit when handle is pulled - you can
see the bottom of the (plastic) cistern "wobble",maybe it opens it up
enough to leak a bit. The flush pipe wiggles too.
Alex, yes I did put the washer on the inside. I've put some silicone
sealer on now - mostly on outside as can't get decent acess inside
without taking it all off the wall and apart. I let it dry for about
five hours, then released the ballcock arm to put the water back on
and seems ok so far.
Grunthos, yes i might have overtightened it. (why don't they say in
the instructions - obviously i'm not a professional).
I think in future it might be better to assemble it as far as
possible, including the flush pipe, before fixing it to the wall,
whiile it is easy to fiddle with.
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