Cistern overflow

[The Medway Handyman]

Working in an 'about to be rented out' flat t'other day & noticed the newly installed WC didn't have an overflow. Held to ball valve down till the cistern was nearly full, no overflow. Old style ball valve & siphon.

I can see a blanking plug at the bottom where the overflow should be.

Problem is the pipework behind the WC is boxed in & is newly tiled. Only adjacent drain is the soil pipe.

If I connect the overflow to the soil pipe, assuming there is an adaptor it will have to go via a trap surely? This doesn't sound like a good idea to me.

The only other easy options are change the siphon to an internal overflow or take a pipe out through the wall.

Any thoughts?

[Grimly Curmudgeon]

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember "The Medway Handyman" saying something like:

A trap to avoid smells, yes; and the flow would have to be visible.

Much easier to fit an internal overflow siphon, imo.

[Andy Hall]

I have seen that done. The hookup was to a special fitting under an adjacent basin on the room side of the trap. It wasn't a thing of beauty. I suppose you could fabricate a trap out of overflow elbows and tubes and drop that to a strap on boss on the soil pipe. There are adaptors from overflow size up to 32mm. For a small drip type of failure, that would probably be OK, but probably not for a catastrophic one. Moreover, there wouldn't normally be a flow of water in the trap and eventually it would dry out. A HepVO trap would avoid that issue, I suppose, but it's all getting rather OTT then.

I would change the siphon. Considering the application of a rented out flat, this is the low maintenance approach.

[The Medway Handyman]

Of course - visible flow - hadn't thought of that, thanks

Looks like a change of siphon.

[Andy Hall]

You can get a tundish for this application, but by the time you've bought and fitted that and a trap and have the resulting ugly solution, it isn't worth it.

[Harry Bloomfield]

Andy Hall expressed precisely :

I have seen botched (flattened pipework) overflows which run under the toilet seat and down into the pan. If the cistern does overflow it is obvious and no need for traps. Is there not a commercial system like this?