Plumbing question.......

[andrewws]

To the plumbers out there, I hope this is the right forum for this question?

Have you ever used plastic pipework on a pumped indirect water heating circuit? It seems that this is posible if you use copper within 100 cm of the boiler. It would all be in 22mm pipe, the John Guest web site says it's possible. But I am a bit nervous about the extremes of temperature, but to run copper in this particular application will be a real pain (listed building).

Just wondered if you would have the same concerns, thanks in advance for any comment.

[jaybkay]

I get involved with a fair amount of plumbing in NZ. Here you have to have a metre of copper pipe from any hot water cylinder, after that 99.9% of installations now get plastic. All back boilers must have only copper pipes.
With a pumped indirect system the problem would be if the pump failed and the thermostat failed, which is much the same scenario as thermostat failure on a stand alone cylinder. So I would expect the ultimate answer is that it will be legal to use plastic after the first metre, as the metre of pipe will lose a lot of heat so preventing failure of the plastic (which is rated up to 80 from memory, which probably mans it won't fail till near boiling).
obviously make sure that the vents for the water system are correct, no problem if yours is an open vented set up (ie with header tank) as the system can't go over 100

[andrewws]

Thanks, the system will be fully vented to a header tank. I cannot see why it can't be done in plastic in that case, just seems a bit strange using plastic. Saying that who would have thought 5 years ago that most plumbing in the UK would have been in plastic?

[Ferg]

andrewws said:

Thanks, the system will be fully vented to a header tank. I cannot see why it can't be done in plastic in that case, just seems a bit strange using plastic. Saying that who would have thought 5 years ago that most plumbing in the UK would have been in plastic?

Having seen some of the problems with pipework less than 10 years old in domestic installations there is absolutely no way I'd use plastic on even domestic hot water in my own house and I'd try to disuade customers from doing it as well. If you must, then I'd use a crimped system and certainly not Speedfit.

[B17NNS]

'Traditional' plumbers will frown on it for no reason other than they are used to copper.

A lot of new build is plumbed in plastic now. I have just re-plumbed a house throughout in plastic (other than rad tails and within the specified clearance of the boiler.

The product is designed for this purpose and as such you should have no issues using it.

[Ferg]

B17NNS said:

'Traditional' plumbers will frown on it for no reason other than they are used to copper.

I, however, frown on it because it isn't as good as copper and is fitted purely for cheapness whether that be in the product or the labour time.
We're already seeing failures out there less than a decade after it became widespread. Those of us who rely on our reputations will always recommend doing the job properly.
I've not seen many failures in crimped systems, but simply due to the number of them being installed I'm not surprised. Like most things in the building industry these days the end user (at least of the house-basher properties) is seemingly more ready to put up with a 2nd rate job.