I need to add a couple of tees to a sealed central heating system.
It is a large one with more than 400 litres of water in it.
I am thinking of leaving some large radiators full of water by closing both valves in each of them and drain the rest of the system. Then cut the pipes and solder.
By leaving some radiators full of water I save time (shorter draining, less venting etc.), water and inhibitor.
Can this be done or will I run the risk of unexpected water ruining the soldering?
I did this a little while ago by freezing the pipes. I looked at the kit you can buy from B&Q and when I had recovered from the shock of seeing the price I had a think and wondered if you could do the same thing with butane. I ended up buying a few tins of butane for 60p each from a cheap shop and then wrapping the pipe in old socks, making a pipe from a length of thin copper tube and injecting the butane into the sock. I have a temperature probe, bought for cooking, and within a minute or two the temperature was -15C. I know it is obvious, but I suppose I ought to say it, if you try this makes sure it is well ventilated and no naked flames etc. etc. It got so bloody cold that I reckon it would have stayed frozen for a couple of hours, especially if it was wrapped in silver foil.
You can probably get cold enough by mixing salt and crushed ice.. its cheaper than butane and probably safer. You need at least as much ice as the quantity of water you need to freeze so don't think a couple of ice cube trays is enough.
Do you have to solder? For grafting bits onto an existing system, I find that a service valve (full bore) and a pushfit fitting of some sort (cuprofit look almost as neat as capillary) will let you cut into a "live" system and not lose more than a cup full of water. You can then extend at your leisure and use the valves to finally bring the new bit online.
is that wise if you are going to then solder the tee's??? I do hope you have some bloody good insurance
By 'live' do you mean full of water under header tank pressure?
Yup, or on a sealed system - just drain a little water from it to drop the pressure before you start. (a couple of litres will normally be enough).
My preferred technique is have the fitting and valve ready assembled, and use a pipe cutter on the offending pipe (close to somewhere like a rad valve so that there will only be water flow from one direction). Once it starts to hiss, cut a bit further, and then give a sharp wiggle to snap off the pipe, placing your thumb over the wet end as you do. Now pick up the prepared fitting, and swap its position for your thumb. Finally wipe your glasses to remove the splashes! ;-)
(Old towel under the work area of course!)
Pretty much exactly what I did when I last added to the central heating, as it was under the (ground!) floor floorboards, spillage wasn't really an issue (Other than the bit that always spurts up directly into your face, of course!)
Toby...
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The only way to do it.
Who dares wins huh?
I'll bear that in mind...
Sure - show it who is boss!
Just don't do what a mate of mine did... needed to get a compression service valve onto a rad feed and return pipes such that they could be split to add a new rad. I had described the technique well enough I thought - I was upstairs when I heard the yell. Came down to find one rather wet looking chap standing next to a rad tail with service valve attached, and a floor and ceiling covered with black gloop! He said, "you can do the other side!". So, cut, wiggle, thumb, pre-assembled valve on and held down to obstruct 85% of the flow, quick turn with a spanner to halt the rest, before finally tightening into final position. While watching he then said, "oh, I see - you put the whole valve on in one go..."
Turns out that having cut the pipe, he then set about sliding over first the backnut, then olive, then valve body, all the time doing the thumb hokey-kokey before finally attempting to get them all together and doing up the nut.
This sort of thing?
That mixture will hold fairly close to 0C but will be pull heat from it's surroundings whilst doing it. It might be able to freeze a pipe provided you can ensuer that it is getting it's heat from the pipe and water rather than the room in general. Certainly wouldn't be as quick as a proper pipe freezer or the butane trick (that's for use in extremis only I think).
This simple maintenace of a a CH system has popped up several times recently. Provided the system is sealed, as in a proper sealed system or a open vented one with bungs in the feed and expansion pipes then as no air can get in no water(*) can get out. Just remember to only have *one* opening at any one time.
(*) Or only minimal like a mug full so still best to have some catching equipment and old towels about.
ROFL, that needs to go in the FAQ next to Expanding Foam. B-)
And that includes NOT flushing a loo halfway through the job, and having the cisten ballcock open and let half a tank of scalding hot water over your wife, who is still upstairs in the other bathroom you left to have a pee..
Depends on the state of the pipe really. Pushfit does not usually care about it being bright and shiny in the way solder does.
I suggest you try it.. It can get down to -8C with ease.
Pipe freezers also get heat from the surroundings, you need an insulated container of some sort, e.g. tape a bag around the pipe and wrap it in cloth to insulate it.
One of the advantages of mains pressure hot water such as combis.
I don't get this. The CH circulating water system is totaly isolated from the distribution of potable water to the places that use it. Surely this is even the case with these new fangled pressurised combi systems that I really know naff all about.
Well, in the end I was right.
I closed both valves in most of the large radiators and let a few small ones in different floors drain.
I selected a point to cut the pipe slightly higher than the drain c*ck.
Sure, there was water coming out of the drain c*ck in spurs, at random intervals, but it had no pressure.
The pipe was dry at the point of the cut, which allowed me to solder without a hitch.
When I reopened the radiator valves the system had still about 1 bar of pressure, without adding any new water. Needless to say that this saved a lot of time and inhibitor.
Pipe freezing , or using push-fit valve fittings, is something that I am well aware of (I have a pipe freezing kit) but I did want to use capillary because the tees are going to be put under a lot of stress and it give me more piece of mind. Being a 22mm pipe, and wanting to solder, made pipe freezing out of the question.
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