Valves: eh?

[bigcat]

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

thanks, NT

[John Stumbles]

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

[Set Square]

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.

[bigcat]

because it

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

[Dave Winters]

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 here:

and the rest of my system is running sweetly, keeping the rest of the house toasty warm.

Dave.

[nightjar]

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.

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

[Dave]

[e-mail] wrote: ... snipped

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

[bigcat]

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.

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

[bigcat]

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

[Christian McArdle]

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.