On 26/11/2019 09:15, harry wrote:
On Monday, 25 November 2019 21:36:02 UTC, John Rumm wrote:
On 25/11/2019 16:45, harry wrote:

You seem to have a valve with dual function. These are often two separate valves. Functions a-
1. To reduce the water pressure (PRV/pressure reducing valve)
2. To relieve excess pressure if the PRV goes faulty (SV/safety valve.)
The PRV will have a high pressure inlet and a lower pressure outlet.

The SV will have an outlet to air to discharge any over pressure.

No, the outlet of the valve must not discharge to air - this would be
prohibited by building regulations. See approved document G section 3.

In an operating situation the water released could be at high pressure
and close to boiling point!

The relieve valves (both main cold water valve, and the additional over
temperature / pressure valve), must be piped to a safe location for
final discharge. There must also be an air break (a tundish) visible for
inspection.

A tun dish; ie to air.

No, a tundish introduces an air break (to protect the mains supply from
back contamination) - the water is still contained and it carried by a
pipe for safe disposal from the tundish.


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/