Hi


I need isolating valves for the CH so I can take rads off and still run
the rest. I've got 15mm or half inch copper, little room to play with,
and 2-3m of pipe will be hanging off the valves in some locations, so
I'm thinking compression rather than pushfit. Compression would also
make reassembly easier, with egtting everything lined up.

I ask cos Ive heard there are issues with full flow or not - which of
the following screwfixes ok for CH? Whats the difference? I know diddly
about water valves.

13483 79p p290 (I see they have an arrow on, I dont know which way the
water flows).

17447 =A31.20 p290

18796 2.29 p291

19933 2.29 p291

21860 3.19 p291

http://www.screwfix.com/


thanks,
NT

wrote:
Hi


I need isolating valves for the CH so I can take rads off and still run
the rest. I've got 15mm or half inch copper, little room to play with,
and 2-3m of pipe will be hanging off the valves in some locations, so
I'm thinking compression rather than pushfit. Compression would also
make reassembly easier, with egtting everything lined up.

I ask cos Ive heard there are issues with full flow or not - which of
the following screwfixes ok for CH? Whats the difference? I know diddly
about water valves.

13483 79p p290 (I see they have an arrow on, I dont know which way the
water flows).

the arrow is only significant for mains pressure use. The slight
restriction should make sod all difference to CH - these should be ok


17447 £1.20 p290

18796 2.29 p291

19933 2.29 p291

21860 3.19 p291

http://www.screwfix.com/


thanks,
NT

In an earlier contribution to this discussion,
wrote:
Hi


I need isolating valves for the CH so I can take rads off and still
run the rest. I've got 15mm or half inch copper, little room to play
with, and 2-3m of pipe will be hanging off the valves in some
locations, so I'm thinking compression rather than pushfit.
Compression would also make reassembly easier, with egtting
everything lined up.

I ask cos Ive heard there are issues with full flow or not - which of
the following screwfixes ok for CH? Whats the difference? I know
diddly about water valves.

13483 79p p290 (I see they have an arrow on, I dont know which way the
water flows).

17447 £1.20 p290

18796 2.29 p291

19933 2.29 p291

21860 3.19 p291

http://www.screwfix.com/


thanks,
NT

Only the very last of your examples is full bore. You can tell because it
says so(!) and because it is very much fatter in the ball area - allowing
space for a big enough ball to have a 13mm or so hole through it.

Whether or not it matters depends on the size of radiator. The others are
likely to have a bore in the region of 6-8mm - which is ok for small to
moderate rads, but too restrictive for large ones.

It's easy enough to determine flow direction. Water flows *into* the
radiator through the hotter pipe and *out* through the cooler pipe.
--
Cheers,
Set Square

Set Square wrote:
In an earlier contribution to this discussion,
wrote:
Hi


I need isolating valves for the CH so I can take rads off and still
run the rest. I've got 15mm or half inch copper, little room to
play
with, and 2-3m of pipe will be hanging off the valves in some
locations, so I'm thinking compression rather than pushfit.
Compression would also make reassembly easier, with egtting
everything lined up.

I ask cos Ive heard there are issues with full flow or not - which
of
the following screwfixes ok for CH? Whats the difference? I know
diddly about water valves.

13483 79p p290 (I see they have an arrow on, I dont know which way
the
water flows).

17447 =A31.20 p290

18796 2.29 p291

19933 2.29 p291

21860 3.19 p291

http://www.screwfix.com/


thanks,
NT

Only the very last of your examples is full bore. You can tell
because it
says so(!) and because it is very much fatter in the ball area -
allowing
space for a big enough ball to have a 13mm or so hole through it.

Whether or not it matters depends on the size of radiator. The others
are
likely to have a bore in the region of 6-8mm - which is ok for small
to
moderate rads, but too restrictive for large ones.

It's easy enough to determine flow direction. Water flows *into* the
radiator through the hotter pipe and *out* through the cooler pipe.
--
Cheers,
Set Square

FWIW there are 3' x 2' rads with the valves turned down a lot, plus a
bigger one set to full on. I gather there is agreement the 3' rads
should be fine on the cheaper valves, but not sure about the bigger
rad.

I could do with a clue on pipe freezing too, would be considerably
easier than drain the whole thing down. Presumably I'd need to freeze
both the rad pipes, and I'm guessing the quoted upto 35 minutes means
15-20 IRL.

That also leaves the q of the best way to cut the pipes: some of them
are up against the wall, making a hand held rotating wheel thingy
un-fittable-in-there. Angle grinder??


I can see it all going horribly wrong.... the ice plug prematurely
melted by the CH coming on when its not meant to, then the ice plug
shaken out by the angle grinder, the grinder showering live water
everywhere, the inaccessible stopcock being inaccessible, and the
entire system of black sludge being dumped over 2 floors of dwelling.
And the CH constantly filling with air once its all sorted. Heh, can
you tell I've not done this b4?


cheers, NT

wrote in message
oups.com...
Hi


I need isolating valves for the CH so I can take rads off and still run
the rest.


Maybe I'm misunderstanding here because I've already announced to the group
that, to me, central heating is more akin to black magic but why would you
need seperate isolating valves? I've just taken a rad off the wall to
decorate behind it and all I did was to close the wheelhead valve and the
lockshield valve (as per instructions he
http://www.diydoctor.org.uk/projects...a_radiator.htm) and the rest
of my system is running sweetly, keeping the rest of the house toasty warm.

Dave.

wrote in message
oups.com...
.....
I could do with a clue on pipe freezing too, would be considerably
easier than drain the whole thing down. Presumably I'd need to freeze
both the rad pipes, and I'm guessing the quoted upto 35 minutes means
15-20 IRL.

When I used pipe freezer, my main probem was the time it took to thaw out
before I could try the stopcock I had fitted. It is important that you only
freeze a straight run of pipe and that you make sure that the ice plug is
long enough.

That also leaves the q of the best way to cut the pipes: some of them
are up against the wall, making a hand held rotating wheel thingy
un-fittable-in-there.

There are compact pipe cutters, which only need as much room behind a pipe
as given by a normal pipe clip. I prefer them to the adjustable sort, but
you do need one cutter for each size of pipe. Otherwise, use a hacksaw blade
in one of the handles designed to hold broken hacksaw blades. However, the
cut will need cleaning up after if you do it that way.

Colin Bignell

wrote:
.... snipped

I could do with a clue on pipe freezing too, would be considerably
easier than drain the whole thing down. Presumably I'd need to freeze
both the rad pipes, and I'm guessing the quoted upto 35 minutes means
15-20 IRL.

The "professional" freezers are very expensive to hire and I haven't had
any success with them on C/H systems, maybe it's the additives or maybe
it's my impatience.
On a vented system I find it much easier to use a pushfit end cap to
seal the expansion pipe and to use something (wine bottle stopper?) to
seal the header tank outlet; if you let a small amount of water out of
the drain point it's safe to work.

.... snipped

--
Dave S
(The return email address is a dummy)

nightjar wrote:
wrote in message
oups.com...
....
I could do with a clue on pipe freezing too, would be considerably
easier than drain the whole thing down. Presumably I'd need to
freeze
both the rad pipes, and I'm guessing the quoted upto 35 minutes
means
15-20 IRL.

When I used pipe freezer, my main probem was the time it took to thaw
out
before I could try the stopcock I had fitted. It is important that
you only
freeze a straight run of pipe and that you make sure that the ice
plug is
long enough.

that sounds like a problem then... on 2 of the rads I've got just 4" or
so of riser to play with, and thats what I need to cut to put valves
in.

That also leaves the q of the best way to cut the pipes: some of
them
are up against the wall, making a hand held rotating wheel thingy
un-fittable-in-there.

There are compact pipe cutters, which only need as much room behind a
pipe
as given by a normal pipe clip.

I dont have that on one of them, the pipes against the wall. :/ Angle
grinder it is I think. Hacksaws not going to be practical here - but
nors the mess created by an angle job.


Thanks Colin.
NT

Dave Winters wrote:
wrote in message
oups.com...
Hi


I need isolating valves for the CH so I can take rads off and still
run
the rest.


Maybe I'm misunderstanding here because I've already announced to the
group
that, to me, central heating is more akin to black magic but why
would you
need seperate isolating valves? I've just taken a rad off the wall to

decorate behind it and all I did was to close the wheelhead valve and
the
lockshield valve (as per instructions he
http://www.diydoctor.org.uk/projects...a_radiator.htm) and the
rest
of my system is running sweetly, keeping the rest of the house toasty
warm.

Dave.

aha ty, this shows how little I know about CH. I was assuming I'd have
to remove the 2 end valves because on one rad there is no possible
movement of the 4" riser pipes, theyre cemented into the floor.

When those are unscrweed as the link says, do the pipes need to move
sideways at all to get the rad out, or not? That is the key q methinks.

BTW I've got TRVs, can i rely on them to close and stay closed?


Thanks!

NT

BTW I've got TRVs, can i rely on them to close and stay closed?

Not usually. However, there are 3 solutions.

1. Some TRVs have a genuine off position that isn't the frost guard setting.
2. Most TRVs allow you to install a "decorators" cap instead of the TRV
head.
3. Most TRVs allow you to put a suitably terminated stop end on the valve
outlet, so it doesn't matter if they open.

Christian.