Replacing cast iron with plastic or copper?

My central heating system is cast iron (old house) in parts its leaking so i am planning on replacing it room by room. I was going to use copper as i have used this before - but someone suggested using plastic as its easier to fit and is just as good, so i did a little research and i have come across a lot of pro's and cons to using plastic, from bowing pipes under high temp to mice chewing through pipes.
Is plastic the way to go?

well i was gonna have my usual rant BUT i can't be bothered

Rant away kev, but if its more than a page long i'll av to do you in with you own wrench.
Also i know that you can't have plastic to within 1 metre of your boiler but what about immersion heater is it advised to adhere to the same principle in regards to this.

personally i wouldn't have the stuff within a metre of the house

then again i am a old dino
as for the immersion it can't do any harm

I'm a little bit dinosaur but not quite as extinct or fossilised as Kev

I use Hep20 quite frequently and have no problems with it, however I dont like using it on any pipework that is on show or is not likely to be boxed in.
If vermin were an existing problem then I would also rule it out.

I dont like Speedfit with the exception of their stop end fittings.

Other makes of plastic come under the category of 'crap they sell in the sheds' I only ever use said crap in an emergency.

Everyone has their own philosophies, experiences and practices and this is just mine. Hep fittings come with instructions and if you follow them and use comon sense then you should have no problems. The same could well go for other makes of pipe but I just never go there.

Hep20 came out in about 1979/80 as 'Acorn' fittings The idea was that you used just the fittings on copper pipe. The plastic pipe was not available for a while after the launch. [I still have a leaflet for them kicking about here somewhere.] This in itself made life a lot easier for me and I suggest you consider this method if you are looking for a compromise.

Around about 1991 I fitted my sisters heating system on a budget with the now re-launched and re-coloured Hep20 in microbore using second hand radiators and a ferroli boiler. The same system is still going strong today even though I was supposed to go round and change a leaking PRV over 2 years ago.

Top tips
Use the proper cutting tool for the plastic pipe.
Ditto for copper.
Dont forget the inserts. Develop a routine so you dont miss any out.
Dont expect the fittings to grip on chrome pipe.
If you have any doubts about whether the fitting is on properly TAKE IT APART TO CHECK
Check each fitting has all of its components and is correctly assembled before you use it.
Dont use pipe that has been kinked or fit it in an overstressed position or against anything where expansion and contraction can cause the pipe to rub and wear.
READ THE INSTRUCTIONS

My experience and preferences are almost exactly the same as Sbdc's.

Copper tube is nicer to look at, but plastic pipe is much quicker to install.

Like Slugbaby, I use only Hep2o pipe and pushfit fittings. Occasionally, on basins, I use John Guest tap connectors, because they allow the pipe to turn and have luvverly big brass nuts to get a spanner onto.

If you use push-fit fittings, then, as Slugbaby said, check every fitting for missing parts, and get used to the feel of how they push onto pipe - very occasionally I find a faulty grab ring (aka grap wedge).

Before installation I don't allow my Hep pipe to come into contact with anything other than Hep pipe, softwood, or a plastic bag - if it gets scratched then I discard it. Many people aren't that careful, and I don't think it's a coincidence that I've never had a leak on an O ring.

Never, ever, omit the insert on plastic pipe.

Some people point out that plastic can't cope with the high temperatures that could result from a boiler thermostat failure. There's an easy answer to this, which is to fit a thermostat on the boiler flow and use it as a safety cut-out; this is something I've considered doing but not done yet.

With regard to bowing when hot, if you follow the MIs wrt pipe clips then there won't be problem.

I wouldn't fit plastic in the loft with a thatched roof - the mice would have a heyday.