Pressure reducing valves - do any work with zero flow?
 

Looking at pressure reducing valves available from Toolststion,
Screwfix and such I note that a lot of the reviews say that the
pressure builds up when there's no flow. I.e. the pressure reduction
reduces the pressure available when running a tap or (more to the
point possibly) a shower but when all taps are turned off the outlet
pressure builds up to match the inlet pressure.

I need to reduce the pressure to some small waterers (as in things for
animals to drink from) which will, if they are working, reduce the
flow to zero. Can one get pressure reduction valves for this sort of
application?

--
Chris Green
·

Pressure reducing valves - do any work with zero flow?
 

On Sat, 1 Aug 2020 12:20:25 +0100, Chris Green wrote:

Looking at pressure reducing valves available from Toolststion,
Screwfix and such I note that a lot of the reviews say that the
pressure builds up when there's no flow. I.e. the pressure reduction
reduces the pressure available when running a tap or (more to the
point possibly) a shower but when all taps are turned off the outlet
pressure builds up to match the inlet pressure.

Not on the one I have here. It holds the outlet pressure at the set
point pretty well. 2.5 bar IIRC with a supply around 4 to 5 bar.
Washing machine and electric shower share the same cold supply, both
can be used at the same time without any temperature changes from the
shower. There is brief pulse in the shower flow as the W/Mc abruptly
open/closes its valve but that is all.

I need to reduce the pressure to some small waterers (as in things for
animals to drink from) ...

Bear in mind that a PRV is spring biased one way valve. If part of
the system freezes the expansion cannot "escape" up the supply, so it
finds somewhere else, pushes a joint apart, splits the pipe...

The one way valve action can also "trap" water hammer pressure
pulses, which may not be producing an audible bang.

--
Cheers
Dave.

Pressure reducing valves - do any work with zero flow?
 

On Saturday, 1 August 2020 12:33:04 UTC+1, Chris Green wrote:
Looking at pressure reducing valves available from Toolststion,
Screwfix and such I note that a lot of the reviews say that the
pressure builds up when there's no flow. I.e. the pressure reduction
reduces the pressure available when running a tap or (more to the
point possibly) a shower but when all taps are turned off the outlet
pressure builds up to match the inlet pressure.

I need to reduce the pressure to some small waterers (as in things for
animals to drink from) which will, if they are working, reduce the
flow to zero. Can one get pressure reduction valves for this sort of
application?

--
Chris Green
·

It depends on the nature of the valve seat.
Metal to metal ones are eroded by the fluid passing through and start to pass on zero flow.

Some have plastic or rubber obturating plate that remains tight for longer but usually they don't maintain as accurate a flow.

What usually happens is the safety valve (downstream of the PRV) lifts and lets the excess away. But they too suffer from the same problem of wear on the seat.