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

long ironer wrote:

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.

Don't take this as a definitive answer, just the results of my
experience with the things...

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)?

Not sure there is any real difference.

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?

This is your traditional sstopcock type of tap. The do reduce flow a bit
(and cause some water hammer) but, as you way with mains pressure not
much of an issue. They are prone to seizing up if you open them hard
against the end stop (always better to open fully and then close a half
turn)

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?

They can work on pressurised systems. They do have many limitations and
are generally best avoided (they also have a habit of breaking
internally such that the knob still spins by the valve does not actually
move). However they are handy for where you want to regulate flow though
(like balancing zones in a CH system).

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.

You can get these in full bore as well. In fact it is often not worth
buying anything other than full bore.

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.

Yup. If not often used then they can get stiff due to scale in hard
water areas.

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?

I tend to use these (or the similar butterfly valves) as a general
replacement for gate valves. Any place you need to provide a way of
shutting off water for maintenance and pipework alteration.

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?

The tap type is ok as a stop valve, but not usually used for a service
valve.

Gate valves are best avoided unless you just want either a cheap
temporary stop, or a way of regulating flow in a system.

Ball valves for pretty much every other application. I tend to use
screwdriver operated ones where they are partially visible or you don't
want or expect them to be used often (under sinks, drain point on the
CH), and the leaver type for things like the feed from a cistern to a
hot water cylinder, or the shut-off valves either side of a shower pump
or in-line filter on a CH system.

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?

Don't know.

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..

This is for the fill to a toilet cistern or a main header tank? Toilet
cistern I would use a screwdriver operated full bore ball valve. In a
loft/airing cupboard then a leaver operated full bore ball valve.



--
Cheers,

John.

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