Cistern siphon is the internal overflow type,can anyone who has experience
of these please tell me if they can be relied on and are they fitted as
standard on new installations.They are new to me but I am not in the
I've got one in my bathroom and it's been fine. Wish I'd known about them
when I put in a downstairs loo as the only place I could run an overflow was
into the garage. They aren't actually syphons, they just open a valve on the
bottom of the valve and just release the water into the pan. Much better in
I agree, but in the UK, AFAIK these things are not legal. The idea of a
syphonic type is that water cannot continue to trickle over into the pan
without anyone knowing about it, neither can water back its way into the
The type Paul mentions is not, I think what the OP is talking about,
although it does work well. But syphonic ones work well and are ubiquitous
in the UK.
These valves do, in fact have wras approval. Screwfix sell them as do
suppliers of fitted bathroom furniture. I can't see why they they wouldn't
meet the regs as back-siphonage is just as improbable as with a syphon. Just
because syphons are ubiquitous tot he UK doesn't mean that new ideas
shouldn't be introduced. In fact these units give a more powerful flush as
the water gushes much more quickly meaning that you can have a much smaller
cistern using less water.
They should be.
Test it by holding the ballvalve float down so the cistern
overflows at full inlet flow, and make sure the overflow
mechanism can handle this without water spilling out of
cistern via some other path.
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