Several years ago I had a wall-mounted boiler fitted to replace an old
floor mounted one. The subsequent re-organisation of the plumbing has
caused a number of problems since, including the production of
'interesting' sounds from the CH system at various points in the
A couple of years ago I noticed, when preparing to drain and flush the
system, some clumps of nasty brown growth floating in the CH header
tank. Thuis has been observed to re-appear at regular intervals.
This phenomena I think is the result of the configuration of the pipe-
work, in that, at the end of the heating cycle, when the boiler and
pump switch off, I've detected hot water going up the cold-water feed
into the header tank, rather than via the expansion/ overflow pipe. I
have recently felt this [hot] backfeed by putting my hand in the
header tank over the outlet to the boiler.
I'm thinking that this has to do with the reduced 'rise' of the
expansion/ overflow pipe coupled with a more powerful convection-
upflow from the boiler.
It occurred to me that I might use a one-way valve device, which I
discovered recently is known as a 'check valve' thus taking away the
easier route for the hot water backfeed and hopefully reduce the
amount of hot water getting back into the tank, although I think some
may still get in via the overflow pipe].
My questions are these:
 How likely is it that fitting a check valve be successful in
stopping the hot water back-feeding up the inlet pipe, and
 What's the best orientation to fit check-valve, horizontal or
vertical ? [there's space for either and I suspect the vertical
orientation will work best].
- posted 12 years ago