Replacing old toilet siphon. Sealant required?

25 Feb 2003
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United Kingdom
As requested, a new thread :)

I am about to embark on replacing the siphon on a crappy old Fordham Flush Panel (Plumbase say they can order one in for me).

I've already taken out the old one to have a look at it as I was going to replace the diaphragm but the assembly can't be taken apart easily, hence I'm going to get the whole siphon.

On the old siphon there seems to be a ring of sealant where the siphon base joins the down pipe. This is on the inside of the cistern, so it is immersed in the water. So, what is this sealant, should I use it on the new siphon, and what is the exact correct way to apply it?

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I'm not sure that anyone requested that you start a new thread, and I wouldn't even have had to mention it if you'd read the rules before posting :rolleyes:

Anyway, my personal method is NOT to put any sealant on the inside of the cistern, as long as the washer supplied is in good condition.

However, the threaded stem of the syphon is invariable a smaller diameter than the hole through which is pokes - I usually fill the resultant gap with best quality (e.g. Dow Corning) mildew resistant sanitary silicone sealant; then put a poly washer underneath; then the backnut.

The last part all assumes that it's a cistern/syphon that has a backnut - I surmise that yours does.

Does this answer your question?

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