Plastic pipes with pushfit fittings or compression fittings Vs Copper

[ST1300]

I am about to convert a bedroom to a bathroom and vice versa but have a dilemma.
My uncle and father were both plumbers and taught me how to DIY safely & correctly. I have always used copper pipes and fittings for years but never pushfit.

My questions are: Should I convert ? Are plastic push fit trustworthy under floors ? Will plastic push fittings last the same time as copper and be as reliable ? Is it better to use plastic pipe with plastic push fittings or with compression joints (do these last longer / are safer?) I would greatly appreciate any advice.

 

[Ermintrude]

You shouldn't have a mechanical fitting in an inaccessible place. I consider that to be under a floor. Plastic pipe is fine. Use joints above floor. I think that plastic fittings are better on plastic pipe as they are not as likely to come undone through movement of the plastic.

I prefer copper but do have plastic in my own home

 

[Whyme]

Compression fittings are fine on plastic pipe but you need the strengthening inserts to stop the olive crushing the pipe thus reducing the internal bore. it's horses for course's if needs must then yes as a choice not for me.

 

[Best]

Depends really how good you can DIY in plumbing!
If you can't solder really well, or do the odd final brass connection up that will hold weep free for a lifetime, then maybe you should learn plastic.
If you can do copper well, then why bother thinking of doing just one little bathroom job in plastic?
Copper pipe, bent in a bender & soldered joints is the way I prefer.

 

[ST1300]

I have read that plastic is non toxic, lasts longer (as copper is susceptible to corrosion over a long time & furring inside pipes), water flows faster through plastic which is a better insulator & less likely to freeze or burst ?

 

[Best]

I have read that plastic is non toxic, lasts longer (as copper is susceptible to corrosion over a long time & furring inside pipes), water flows faster through plastic which is a better insulator & less likely to freeze or burst ?

Copper has antibacterial properties apparently. I hear that copper (or anything that contains copper, like brass) is excellent for door handles, cooking pans etc, as germs can't survive on it easily.
Plastic is microporous, believe it or not & I wouldn't bet on it not being inhabited by microorganisms.
Plastic is smaller bore than copper because plastic needs to be heavier walled - so flow is reduced that way. Also you can bend copper, but normally have to put 90 degree elbows on plastic in loads of places.
Plastic is more resistant to bursting in frost, but still can, especially plastic fittings.
Mice & rats will chew through plastic fittings & pipe.
UV rays will damage exposed plastic.
On the point of copper corroding, - yes, it can in certain regions due to some water. Plastic would be good there and recommended. However, on heating systems copper is best.

 

[TheWombat]

Plastic looks like a bodge job

By this I mean that it doesn't look right. If it's concealed, so what, but if you have to look at it you won't like the appearance. Or perhaps you will. Either way, here are a few observations.

First off, plastic push-fit seems pretty secure (I use Polyplumb, FWIW, because I was told they were okay when I started and have never had reason to change). But you have to make the joints properly. RTFM! They've introduced plastic stiffeners recently, but I stick to the stainless steel when I can get them.

A few gotchas:

First off, people will tell you that you can buy the pipe cheap in convenient coils. Well, yes you can but the coiled pipe doesn't just unroll to straight lengths. This matters more than you think - as well as the pipework looking wonky, you really want to make sure that the joint is made square and not under strain. You're probably better off buying the 3m straight lengths.

People will tell you that you can bend the plastic pipe easily. This is partly true, especially with 15mm if you're sweeping it around a large radius. I tend to use a bit of bent copper for anything tighter. The plastic will happily bend to get things in line on a long length in relation to the diameter of the pipe (the 22mm is a lot stiffer).

I'm NOT comfortable, at all, using copper compression fittings on it. Some say this is okay. If I need to go to a copper compression fitting I use a straight coupler and a short bit of copper to go in to the copper fitting.

Some say that the bore is reduced by the stiffeners so the flow is reduced over copper. I say this doesn't take in to account the friction of copper vs. plastic, or the reduction the number of elbows as more bends can be swept more easily in plastic.

Plastic is certainly more expensive to buy than end-feed copper, but it's a heck of a lot quicker and I think it's more reliable for anyone who doesn't make solder joints on a regular basis (i.e. gets them right every time).

 

[ST1300]

I have a Vaillant combi boiler only (no tanks or cyclinders) to service the central heating system with 10 rads and one bathroom & shower. What size pipes should be used ?

 

[hammers4spanner]

Black iron

 

[ST1300]

Prefer to use ferrous ferric oxide myself

 

[TheWombat]

I don't want to sound borish or unhelpful, but your you should really RTM for the boiler and use the size of pipe the manufacturer recommends. You haven't even said whether your radiators are sealed or open vented. If you can find an honest and helpful local plumber and pay them for advice and sorting out the tricky bits while you rip up the floors and lay the pipes you could be saving yourself a lot of grief.

As to the size of pipe, we'd normally use 15mm for the radiators, and definitely copper, at least where the pipe is visible. If with ten radiators you might need some of the pipework in larger diameter - 22 or 28mm. Or are they little domestic radiators? Plastic pipe is technically suitable for most heating systems (possibly not close to the boiler). The manufacturers have tested it properly and say so, and I'm happy to take their word for it. But it can look awful and doesn't support components mechanically. Of course, you shouldn't be relying on the connecting pipe to fix a component down. Yeah, right!

Some people like 10mm radiator pipe because it's easy to lay (smaller holes, easy to bend &c). The consensus seems to be that 10mm is too narrow once it's been furred up a bit (empirical evidence is patchy), and 15mm valves and other fittings are a bit more standard anyway. Others may disagree.

But as I said, if you're asking about this kind of stuff you're possibly more out of your depth than you realise. Ten radiators is a lot of water if they're large, so how are you going to distribute it? If you're choosing between copper, steel and plastic pipes, have you considered adjacent building materials attacking the pipework? A good plumber or engineer would know all this, and could tell you what's needed very quickly, but only by being on-site. Messing up the flow through a boiler can kill the boiler, and be potentially dangerous. Paying a plumber or engineer for a couple of half days for advice and the tricky bits could save you a great deal of money and grief. (Calling in a professional for a "free quote" would, of course, be rude; but you'd only get a salesman turning up anyway).

 

[ST1300]

It is a sealed system (no tanks or cylinders as I said) with a Vaillant combi with a built in pump. I understand the pipework for the boiler but its whether to use 15mm or larger to service the radiators as there is only 15mm presently for normal domestic double rads. I wouldn't use any other than copper for the heating system.

 

[ST1300]

It is a sealed system (as I said no tanks or cylinders) with a Vaillant combi with built in pump for the heating system. I know the size of pipes for boiler but querying what size pipes 15mm or above for the large amount of double domestic sized rads with TRV's should be used. I would only ever fit copper on heating systems.

 

[Duker996]

It depends how many btu's the rads require as to how you size the pipes. Much like a 2.5mm cable won't be suitible for a 10.5kw shower!

 

[ST1300]

Oh no another job to do .........