Many thanks to posters for recent help on feed pipe positions for the
new CW cistern. I have now got hold of a copy of the Water Regs Guide,
hence another question.

What are the precise definitions of 'stop valve' and 'servicing valve'
for the water regs purposes (they aren't defined, so far as I can see)?

IME 4 types of valve are on sale viz:

a. Brass units with tap style handles, sold as stop valves which screw
down a washer like standard taps. I suspect these restrict flow
diameter, but mains water pressure is such that it doesn't make much
difference - is that right?

b. Gate valves, which IME allow sepage when closed once they are a year
or two old, & SFAIUI are unsuitable for pressurised systems, but the
gate valve opens to provide a clear straight through bore, that is full
flow. Are these now obsolescent?

c. In-line units sold as service valves - usually with a chisel screw
head for operation with a screwdriver. On these an internal ball valve
is rotated by the screwdriver. Flow is usually restricted because the
internal ball dia is usually less than the connecting Cu diameters.
These appear to be suitable for normal domestic water temperatures and
pressures. Valves for washing machine supply pipes seem to be a
variant of this with a small lever for operation instead of a screw
head.

d. Ball type valves operated by a lever. Otherwise similar in style to
c, the ball diameter is larger allowing full flow at the connecting Cu
diameter. What operational conditions are these suitable for?


So which of these 4 types are suitable for use as a stop valve, and
which as service valves? Indeed what are the correct applications of
the above valves?

A long time ago (mid 90s) a water board inspector told me that service
valves had to be operated by a screwdriver. I can't see that in the
regs, so is it still correct?

A problem I have is that ideally the cistern is on the low side, so I'd
prefer to use full flow valves wherever possible to reduce pressure
loss..

Any info much appreciated, TIA