Dave Osborne wrote:
wrote:
I'm after a float valve of some sort which will not get damaged if it
is completely submerged. I want to have a tank which is mostly filled
from local sources of water but, if the local sources dry up, then the
float valve will maintain a foot or so of water in the bottom of the
tank from the mains. (I guess there will have to be strict non-return
precautions to conform to water byelaws too)

So, I need a float valve that won't mind being underwater, I suspect
that the 'standard' sort of cold water tank valve with a big spherical
float won't survive being under water.

Would a Torbeck valve be OK, or do they include the flushing mechanism
which I don't need?


As Andrew said, I would be inclined to use an electrical solution.

A float switch like this:

http://www.maplin.co.uk/Module.aspx?ModuleNo=12167

And a solenoid valve from a washing machine.



Oh, just found this: - perfect

http://www.halstedrain.com/Mains%20W...p%20Valves.pdf

Seems to use a washing machine solenoid valve and a tundish for
non-return isolation.

I had a set-up which did *exactly* this, my design was amazingly like
what's described in the above link to a PDF, down to using a similar
plastic box to put it in.

However they don't survive all that long in an outdoor environment,
even in a shed (which is where mine was). The combination of
occasional freezing and our very high mains water pressure soon breaks
something.

(I guess I may have the same freezing problem with any sort of float
valve but at least they're cheaper)

The www.halstedrain.com site is a bit worrying, no indication of
prices anywhere that I can see.

--
Chris Green