DIY Central Heating

[RatRibs73]

Hi,

I'm planning on upgrading my CH system, boiler & 7 rads, this year. Because I'm DIYing everything (apart from connecting to gas and commisioning) I don't fancy trying to do it all at once so I'm planning to complete in stages. My plan is to replace downstairs rads, while decorating then upstairs rads, again while decorating, and then the boiler.

The existing system is corroding in places, two or three rads and also what looks like some very long term leaks from the pipework in the cellar.

My question is: At what stages would it be best to clean and add protection to the system. I know that a full clean is needed before boiler installation but would it be worth doing this before or after any of the radiator changes? There will probably be about 2-3 weeks between each stage of the installation.

Would it be worth getting the system powerflushed if I'm replacing all the rads?

Also is there any reliable way of telling whether I have imperial or metric copper pipe?

Also, also. What are peoples experieces of getting a plumber round just to commision?

Cheers,

Ribs

[Grunff]

I would strongly recommend doing it all in one go, rather than in a staged approach. It will save you a lot of time and effort. Wait until late spring, when you no longer need the CH, and just shut it down and do it in one go. Going by your description, it shouldn't take more than a long weekend.

Measure the pipe OD with a vernier caliper.

We had our (oil) boiler commissioned by an engineer working for the manufacturer (Grant). No problems.

[Andy Hall]

I think that I would adopt one of two strategies.

- Do the whole job at once and avoid the problem

- Add a cheap (e.g. Screwfix) corrosion inhibitor each time and write off the cost.

It would be a good idea considering converting the system to sealed operation.

Then, if you are throwing out the radiators anyway, you can flush under mains pressure as new radiators are installed at each valve.

However, sealed operation may not be possible with the old boiler, so you may need to do this step towards the end when the old boiler has been removed and before the new one is fitted.

Alternatively you can rent a powerflushing machine. If you are capable of doing the plumbing, you can certainly drive one of these. That is unless you feel like improving Centrica shareholder dividends by spending £600 on a powerflush by BG.

Measure with a vernier caliper.

Assuming a gas boiler, it needs to be done by a CORGI fitter. It would be advisable to identify one first and obtain agreement because in effect he is taking some responsibility for your work - e.g. the flue arrangements. Some fitters may be reluctant to do that if they haven't done the whole job or supplied the boiler. Some phoning around may be necessary. Most good fitters do not have a shortage of work.

[Roger Mills (aka Set Square)]

There is very little difference between 1/2" imperial and 15mm metric, and the fittings - even solder - are interchangeable, so it doesn't matter. [I think imperial is *slightly* bigger, but only by a gnats - so metric fittings are a *bit* tight - but will go on].

However, 3/4" imperial is measurably smaller than 22mm - so a vernier caliper is fine for this. For these, you need special solder fittings which are different sizes at the two ends, or special imperial olives for metric compression fittings. Don't even *think* about push-fit!

[RatRibs73]

I was wanting to do the whole thing in Cuprofit and was aware that you can't use on imperial sizes. Looks like JG Speedfit do a converter but only 1/2" to 15mm and not 3/4" to 22mm. I won't have to be breaking into the flow and return in many places anyway as most rads will be staying in the same place. But where I do I suppose I'll just have to use a couple of compression fittings either side of the new tee. No probs with that.

[RatRibs73]

Problem is that I've had to remove rads in the lounge to plaster. The radiator had rusted onto the valve and the only way I could remove was with a hacksaw! We've only got one rad in the lounge and it's brass monkeys in there now. Would ideally like to just fit the rads in the lounge for now as don't want to be without CH at all at this time of year. If I were to do this would I have to clean the system before and and/or after?

Not sure what you mean

I'll DIY it! You can rent one from Brandon Tool Hire for about =A360. So what you're saying is I could replace all rads etc and as long as I give it a good powerflush before installing the boiler It should be OK?

[Andy Hall]

You could as best of a cleaning job as you can now.

Options here are:

- Rent a powerflush machine. Use, then drain and refill with inhibitor.

- Remove radiators one at a time, take outside and flush through. However, in the light of your rusted on comment, that might not be realistic. Take care if you do this because sludge is an indellible dye. Flush at each radiator valve as you go then fill and fill with inhibitor.

- Put in a sludge treatment and run the system for a week, then flush and fill with inhibitor.

- Flush only, get out as much crud as you can and refill adding inhibitor. Since you are replacing the whole lot within a few months, this could be an option. The inhibitor will stop anything getting much worse at least.

When you have all of the new radiators installed, is the time to do a proper and thorough job before teh boiler goes in.

Look for some postings by Ed Sirett and then go the FAQ mentioned in his signature. That explains the principle of sealed systems which are basically to replace the loft header tank with a pressure vessel and to fill the system from the mains. If you have this, you can use mains pressure water to flush rather than just what the tank provides.

Yes. However, if you have replaced all the radiators and switched to a sealed system you can use the mains for flushing. Remember this may not be possible with existing boiler but may be a requirement for some new boilers which will only run on a sealed system. There are others that will work on either. However, if you stay with an open vented system then a powerflush is probably a good idea.

[Roger Mills (aka Set Square)]

Or just use compression tees, with imperial olives in the 22mm parts.

[Lobster]

I agree, I think you could have problems. CORGIs hate taking on someone else's work to complete, especially a d-i-y-er's, and they're all so busy they simply don't need to. All I would say is find someone who agrees to do what you want before you commit yourself to this path - you might just find yourself with a fully-installed system that nobody will commission for you!

I'm in the midst of installing a CH system myself, and it took me ages to find a CORGI who would agree to commissioning it (and he's only agreed because he thinks I've got a non-CORGI but otherwise competent plumber/fitter installing it! And he did say that he would have to lay the new gas pipe from the meter to the boiler himself, he wouldn't sign off anybody else doing that. (hint - eg it's perfectly possible to pass a drop test (ie, no detectable loss in gas pressure during the engineer's test) where a soldered joint has not actually been soldered yet...!)

David David

[Ed Sirett]

The "22mm" pipe will be around 21.5mm if it's imperial. The "15mm" pipe will be a little more than 15mm if it's imperial.

[RatRibs73]

A general rule of thumb I've used with compression fittings before is to hand tighten and then up to about one full turn with the spanners. Would it be the same using a 22mm compression with an imperial olive?

[Roger Mills (aka Set Square)]

There's no significant difference, in my experience, in the torque required - depending on whether it's a metric olive on 22mm pipe or an imperial olive on 3/4" pipe. In either case, you tighten it until it *feels* right. I certainly wouldn't use any rule of thumb involving numbers of turns - because not all fittings have the same thread pitch - so 1 turn is a lot tighter with a coarse pitch than with a fine one.

[RatRibs73]

Yeah, sorry folks didn't explain that very well. I do follow the above but in my (limited experience) it usually takes roughly one turn. I always err on the side of caution anyway. It's better to undertighten and then just tighten more if you spot a leak rather than overtighten and have to dismantle the bugger and start again.