Plastic Pipe in a Sealed CH System ?

[self builder 123]

Hi

Noticed that we have 2 runs of 15mm plastic pipe going to a towel rail as part of our sealed CH system. All other pipework is copper.

Primary water temperature could be up to 81 deg C with a running pressure at the boiler gauge of approx. 1.5 bar.

I have read that plastic pipe should not be used in a sealed CH system ?

Any comments ?

 

[corgiman]

then you read wrong

of course push fitpipe can be used as long as it is the barrier type

 

[ChrisR]

It's very widely used indeed. But it's true that at the highest temps and pressures you can get in a sealed system, under fault conditions where stats fail, it doesna hold it, cap'n Kirk.
Some boilers like Mexicos are more likely to cause those conditions than a modern combi, say.
Personally I'm more concerned about the longevity of the O rings in pushfit connectors.

Here's one I prepared earlier...

 

[self builder 123]

Cheers

Read it on the Worcester Bosch website.

 

[corgiman]

you probably read that no plastic pipe should be installed within a meter (I think) of the boiler.

 

[self builder 123]

yes that is right - not within 1m of the boiler.

 

[wishiwascorgi]

The development in plastic piping has come a long way in the last few years and we use hep2o as it is the only one i would recommend on heating but polypipe has now managed to perfect their fitting so it too will be capable of working at hotter temperatures.

If you boiler is running at 80C hep20 has a safe pressure level of 7 bar and most boilers have a blow off valve when the pressure hits 3bar. So the only way that the plastic could leak is if it was not fitted right or a mouse/rat chews through it.

Are the pipe and fittings grey or white?

If white i would check on the pipework as it will tell you information about that the pipe and what the maximum temperature is allowed.

Most systems now will be run in plastic as it is a quicker and a cheaper alternative to copper.

The rad in the bathroom will have been added to the system after installation and the plumber has used plastic for speed.

To be honest I would only worry about plastic fittings and pipework if it was on the gas.

 

[wishiwascorgi]

It's very widely used indeed. But it's true that at the highest temps and pressures you can get in a sealed system, under fault conditions where stats fail, it doesna hold it, cap'n Kirk.
Some boilers like Mexicos are more likely to cause those conditions than a modern combi, say.
Personally I'm more concerned about the longevity of the O rings in pushfit connectors.

Here's one I prepared earlier...

This is an older polypipe fitting which can only go upto 82C and 3bar of pressure so if the blow off valve fails the above picture is the outcome and that is why i recommend hep20

 

[self builder 123]

Hi

The pipe work is now covered up so I am unable to tell how the pipe work was connected, but I do remember that the pipework was blue in colour.

The CH system has a PRV which will open at 2.5bar. The oil fired boiler will trip under a fault condition at 111 deg C.

Should I look to have a pipe stat fitted to the flow from the boiler which would trip the system say at 90 deg C. A second safety system.

 

[wishiwascorgi]

ps hep20 states that the system would have a life at LEAST of the traditional installation of metal pipe and fittings.

It has a safe operating pressure and maximum rating at 7bar of 82C and can operate at 3bar at 114C for a limited period in the event of malfunction of the boiler like chris stated

 

[wishiwascorgi]

if it is blue then i might start worrying as it sounds like they have used mdpe pipe. Never seen blue pipe for heating only for towns main.

 

[self builder 123]

Wishiwascorgi

Thanks for your reply.

I am confident that it was not mdpe. I recognise this as being used for mains water running to the house.

I looked up some old notes.

From what I noted down it is a 15mm PE-80 Oxygen Diffuser Barrier Pipe.

Is this PEX pipe and am I ok ? Finger crossed !!!!!

 

[wishiwascorgi]

Yes that should be good as it is mostly used in industrial. Never seen any on a residential installation and they guarantee it for 50 years