any central heating engineers on here ?

[colin1]

I may be getting a new central heating system. My dilemma is plastic pipe or copper pipe.

On the one hand, plastic pipe is cheaper, can be bent into place so less joins, so less chance of leaks, and faster flowing system.

On the other hand, a trainee british gas engineer, told me that although plastic pipes dont leak water, they do leak air, so it's like the difference between stuff in an empty jam jar and stuff with the lid on. The idea being that rust forms in the radiators more easily, if air can get into the system even if it is dissolved into the water rather than creating airlocks.
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[Al]

The plastic pipe is cheaper and much faster to install but then the fittings are more expensive then copper ones.
I always worry about how well the push fit fittings will last aswell, as they only seal on an o-ring which could surely perish over time.
Copper also looks better if you appreciate that kind of thing. However I can't see you having massive problem with either if you use a decent inhibitor and install some sensibly placed auto air vents.

We normally use a mixture of the two types of pipe with copper on show and plastic where it needs to be fed into awkward places.
But we use a plastic pipe that has an alloy Barrier built in, so it offers the best of both worlds. Its made by 'Valsir' but most of the big companies sell the same type of thing.
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[colin1]

do you know if a type of pipe called hep20 by a company called hepworth has an alloy barrier ?

When you say allow barrier, does that mean the pipe is lined with a thing foil barrier, or that their is a thin foil barrier embedded in the pipe ?

Not heard of auto air vents before. Is that a corner that cheaper companies would cut ?
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[Al]

Hepworth do make a barrier pipe according to google but they also do a non barrier version.
The pipe we use has alloy in but this is just because we mainly use it for underfloor heating and it holds its shape once bent. We always refer to the alloy as the barrier but I think the barrier is normally some kind of resin material, the alloy is sandwiched between an inner and outer plastic layer.
An auto air vent is just a little vent that lets air out but not water. It would be fitted on a high point of the system, you may not need one it would depend on the design of the system. Its no different to venting air from a radiator but it does it automatically.
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[kitty kat]

Any decent company would install copper pipe as standard. Good firms have a lot to loose in reputation if the systems leak also with copper it tends to stay put whereas with plastic it should be clipped at least every meter or less and clipped both sides of fittings. If you look inside a 15mm plastic pipe it only has a bore of about 10mm where copper is at least 14mm giving faster flow and quicker heating and less resistance on pumps etc
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[calyx]

Sorry for the late reply, I missed this one somehow..

I am a building services mechanical design consultant. So I think I can give some advice

First things first; boiler means combi boiler. something like this;

https://www.stonewood.org.uk/imagess/boiler.jpeg


Oxygen barrier pipes will not stop oxygen getting into your system. Barrier helps but I wouldn't trust it that much.
A boiler usually dies in 15 years.
If you use plastic pipes your boiler's heat exchanger will get rusty in 5 years time. As a result your pump will struggle + you will lose heat efficiency because the conductivity of the exchanger will be fucked by rust.
Pump will die eventually. Exchanger will definitely survive but your gas bill might increase up to 25% with that exchanger.

You do the maths now.
Go plastic = 25%ish higher bills after 4-5 years, 2 pumps + Labor in 15 years
Go copper = Maybe 1 pump + labour in 15 years.

BTW REHAU (german stuff) do proper low friction oxygen barrier pipes but they cost almost the same as copper pipes. (less labour intensive than copper though)

I would go for plastic for mid and short term.
For a long term solution copper is the best.

If you need a new boiler too. Go for Viessmann. Proper bulletproof.
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Boris - London

[Robby]

I would be worried about plastic pipe fracturing if I did something silly like hit it hard with the hoover, or shove furniture up against it. It may be fine, but it would be a nagging concern that isn't there with copper. I would go with copper.

One thing I would definately spend a bit extra on is a water softener on the cold inlet before the heat exchanger. I live in a very hard water area, so stuff furrs up quickly. My hot water pressure was quite poor on a 5-7 year old boiler, so I recently took the heat exchanger out and descaled it. Massive difference, hot water is now hotter and higher pressure, so I burn about half as much gas running a bath and it runs quicker. Descaling it was a fairly simply process, removal was easy enough (had drained down the central heating to flush out some flush stuff), then I soaked it for a few hours in coca-cola, and then for a couple more hours in a fairly strong phosphoric acid solution. A bit of rinsing later, refitted, and great success.

A new heat exchanger was £60-120, descaling cost me a couple of fibre washers, a few hours of my time, and about a tenner's worth of coke and chemicals. The central heating is also far hotter after a decent descale and addition of corrosion inhibitor. A some point I'll change some of the rads in the flat single row ones, I no longer need double row rads in smaller rooms like bedrooms. This has the added benefit of less heat loss throughout the circuit, currently the last rad on the circuit doesn't get as hot as the others.

Also auto air valves - you can get auto air bleed valves on radiators too. I have one on my bathroom towel rail (Aladdin one, about a tenner on ebay). Not all that convinced by it, it seems to take a fair while to bleed after a fresh system fill so I just go round with the bleed key once a month to do all the rads in the flat. Rarely get anything out now the system is clean inside.

Doing any of the above would probably kill any warranty/boiler service plan/insurance that you may have in place, but it gives you more efficient heating. If its very cold outside then my heating comes on for about 5 minutes twice a day.

One last bit on simple economics. When I first moved in the flat had no cavity wall insulation, no thermostat, no corrosion inhibitor in the system and lots of crap in the system. I was spending £100/month on gas in the winter and it was still cold. I now have all of those things, and I'm spending about £30/month on gas in the winter and the flat is warm.

[colin1]

[calyx]

Viessmann is Europes best selling boiler brand. Story is a bit different in the UK for some reason...

BTW it has:

-Stainless steel combustion chamber. (very rare in the boiler world)
-Grundfoss pump. (rolls royce of pumps)
-German technology
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Boris - London

[calyx]

[quote="Robby"
One thing I would definately spend a bit extra on is a water softener on the cold inlet before the heat exchanger. [/quote]

This is good advice

Something like this;

https://www.barnitts.co.uk/products/details/10017.html

Before the exchanger, after the strainer.
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Boris - London

[Al]

We install Viessmann boilers and also do the some of the local warranty repairs for Viessmann. They are good boilers, very few faults and simple and easy to work on, the casings are pretty compact yet they still seem to have loads of room inside.
Only part i'm not so keen on is the flue as it doesn't lock together in the same way other manufactures do but that is more of an installer preference.
Viessmann do a 5 year warranty but that drops to 3 years I think if its not fitted by one of their registered installers. I think its a 10 year warranty on the heat exchanger whoever fits it.

Although I'm sure the point about plastic pipe and boiler/pump life is valid, I think there is probably more to it then everything just coming to a grinding halt after 5 years. Plenty of houses have had plastic pipe in for more then 5 years without expensive problems. Lots of new builds are having underfloor heating nowadays which is all plastic pipe, I'm sure the boiler manufactures would claim it invalidates the warranty or something if its was damaging boilers that quickly.

Boilers generally don't last as long as they used to though anyway as they have become more complexed and there is just lots more to go wrong. Combi boilers are worse as they have even more to go wrong. My old heat only boiler with its cast iron heat exchanger is about 22 years which you'd never get out of a modern boiler.
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[kitty kat]

Loads of 15 to 20 year plus Worcesters out and still in use. My partner even knows of some 30 year plus Worcesters.
To be honest the rule of thumb is buy cheap expect to replace buy a recognised name with excellent back up and get years of life.
Also dont forget that Worcester and Valiant are also now German Companies and both also have a 10 year warranty on heat exchangers and a 5 year warranty on all other parts and Worcester/Bosch also use Grunfoss pumps
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[colin1]

Manufacturers warranties are only valid if they are serviced every year, which I think is a bit of a scam, as I believe if anything's going to go wrong, it's going to be in the first few months, or after 5 years. I could be wrong though.

Thanks for all the advice though guys. I'm definitely a lot wiser for your input.
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colin1 is officially faster than god

[st3v3]

You have trouble with your plumbing there Col?


..it's worth the

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