Getting hot water into part of a heating system

11 Jan 2013
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United Kingdom
Complex setup- short version, I've put the pipework in for 2 radiators 'cos I wanted to hide the pipework in ceiling and stud walls, there's no boiler fitted and no rads fitted to the ends of the pipework yet (got to finish insulating the ceiling & let BCO have a skeg at it before I board and skim- I'm telling lies there, I'll put the plasterboard up but my plastering is utterly pish so I've got a top chap to do that bit). But I digress.

The joints have been a pain to do (my soldering skills are rusty, double bends to get round timbers, all sorts of nonsense) and they're not going to be easily accessible once plasterboard goes on so I'd really like to give them a near-live test before sealing them up (in a previous life I too came unstuck on a joint that was fine until the system warmed up & then it was drip drip drip).

So I'm contemplating a big fat lashup involving an old galvanised tank I found kicking around the place connected to flow pipe end (which is well above where the radiators will be) via pushfit tap connector (got some kicking around), the return pipe end next to the tank where I can see it, plastic Speedfit loops where the rads will be (or might be easier to temp fit the rads), boil the kettle many times & chuck it in the tank until water comes out of the return, isolate the flow, stick my lethal air pressure tester on the end of the return & pressurise to 4 bar (so air volume will be tiny so any major failure will just be a damp mess)

This is all going to be a massive pain in the bum- does anyone think it'll serve any useful purpose on soldered joints that have already passed a 4 bar air pressure test (and I won't be repeating that having read the many threads on the subject!) or do I really need circulating hot water to check the things properly.

Why copper- solid fuel back boiler is part of the planned system, it'll be connected via a thermal store so copper may be being over cautious but it is what the HETAS installers told me to do so there we go.

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If it's passed a 4bar pressure test. Doing the same test with hot water will not change anything. Unless your solder is made out of chocolate;)
Cheers chap- trouble with this advancing years lark is the old eyesight starts going. Last trip to the opticians I got myself a set of engine mending glasses made (focal length about 6 inches instead of normal reading distance), even using them it's hard to see whether I've got a true solder ring at the top of the fitting or whether it is just charred flux.

And (as in the post) I did get stung years ago- didn't pressure test, filled system with cold, all good, fired boiler, all good for about 30 minutes and then 2 leaks appeared (one at an elbow to the hot water cylinder which had good access & was fairly easy, one at a T next to a joist in the floor which was a complete and utter b*stard, limited access and a slight dip in the run so even after draining there was water in the thing which took a long time to boil off.

On this job so far I've pulled a couple of joints that looked rubbish (the ring didn't have that lovely smooth look) and found that the pipe and fitting were tinned all the way round and all the way to the end so hopefully I'm just being paranoid.

I might give my big blowlamp a go (actually it is fathers' blowlamp, he bought it to put the central heating in their 3rd house. In 1966.)- doing test joints on the bench it seems to get the pipe and fitting too hot too quickly but with the heatsinking effect of long lengths of tube it might be more manageable and with a 30mm diameter nozzle it might give a more even heat than my toy 15mm throwaway butane cylinder thing (fathers' blowlamp still has fathers' 26kg propane bottle on it. Father died in 1978, not sure Calor will want the bottle back but by the weight of it it'll see me out as well :) )

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