Basic plumbing connection questions for bathroom suite

[muffking]

After 2 years of my MFi bathroom suite living in the spare room still in their boxes I have finally got some time off work to be able to fit it, but have some queries now that I've stripped the room.

1) The hot water from my Combi fed the bath tap via a 22mm pipe which T'pieced off to a 15mm to also feed the sink tap. Do I need to retain the 22mm feed to the baths hot tap (bearing in mind that the old pipework was designed for a very old back boiler system) or can I split the 22mm hot water supply to two 15mm pipes?

2) If I have to use a 22mm feed for the bath can I fit an isolator inline without reducing affecting the flow rate?

3) Unless it comes down to personal preference, should I use copper pipes to join the mains & boiler copper pipe supplies to the batroom suite? Also, should I join the pipes with push fit or compression joints?

4) If bath taps & sink taps have standard thread sizes, what are they as I need to get these.

 

[lagunaglen]

1) 15 mm is best from combi to all outlets, so if possible replace all 22mm with 15 mm pipe.
2) just use a 15mm inline isolation valve
3)personally ,for a diy job use plastic pipe, but you must use pipe inserts on all plastic to plastic connections, plastic to copper does not req inserts and plastic to chrome is a definate no no as the fittings wont grip and can blow off.
4)bath taps 3/4" ,you can get a 3/4"-15mm tap connector or flexi
all others are 1/2", so you req a 1/2"-15mm tap connector or flexis.

 

[muffking]

That's perfect, cheers lagunaglen.
When I fit the rads with chrome pipes (i'll go plastic to chrome) 'll be using compression elbows, but am interested to know why plastic inserts are not required when push fitting plastic to copper?

 

[powell30]

Because copper is rigid. Plastic for instance softenens with heat and are liable to slip the grab rings when under pressure. Copper won't

 

[muffking]

Because copper is rigid. Plastic for instance softenens with heat and are liable to slip the grab rings when under pressure. Copper won't

If the plastic pipe softens under heat, why would it not need an insert even when coupled to a copper pipe though?

 

[seco services]

you should use a insert on any plastic pipe, if its going into pushfit, brass fittings etc.

 

[Blasphemous]

seco is right. Use an insert on ANY plastic pipe whatever its going into. You could end up regretting it big time if you don't!

 

[muffking]

I've bought a pack of JG inserts with the rubber rings to go in the plastic pipe which will be push fitted into a 22-15mm reducing coupler and then along to the push fit tap flexis.
I will also use the inserts for the compression elbows where they go to chrome pipes for the rads.

 

[seco services]

if your using compression on chrome pipe copper olives are better.
but i have used either and they have been ok, and jointing compound.