There's a valve in the 'bulb' on the top of your siphon break. Its
probably leaking because you never opened and cleaned it - the exact
same chemical deposition mechanism that clogs shower heads. Soak the
valve in an 'acid' (vinegar, oxalic, muriatic/hydrochloric, "lime
removers", acid based toilet cleaners, etc.) to remove the 'scale'
that has formed on it; or, simply replace the valve as they are cheap.



.. In article , Geoff
Schultz wrote:

The anti-siphon/vented-loop on my generator decides to leak at random. Quite
often it has no problems, but other times I'm seeing a trickle of water
running from it. The unit consists of a semi-circular stainless steel tube
with a plastic bulb on the top of it. When there's pressure the bulb seals
and when the pressure drops the bulb releases and breaks the siphon. I've
removed the bulb and checked it with mouth-pressure, and it seems fine.
There's no build-up on it.

I can't figure out what is causing this leak. The fact that it can come and
go during a single running session seems to indicate something other than a
particle/salt crystal/etc blocking it open. Are there any ideas as to what
might be causing this? Oh, the impeller on the water pump is new.

-- Geoff