Adding new radiators and water / 22mm or 15mm

[danbr]

Hi,

I built a house approximately 2 years ago. We went for the Grant Vortex outdoor combi boiler 26kw.

The plumber at the time has done 22mm runs for hot water and then 15mm reducing tees to the shower, taps etc. Reading the grant manual it says that it all be done in 15mm. At the time, i asked him to run pipes to upstairs for when i convert the upstairs to a living space.

So upstairs i have 2 x 22mm pipes for hot and cold water, is it better to reduce this to 15mm at the earliest point upstairs?

Also, according to the user manual the radiators should be in 22mm and then 15mm to radiator tails. He has run 2 x 15mm pipes to upstairs for flow and return, should i increase this pipe to 22mm at the earliest point upstairs?

This is all in copper

Many Thanks in advance

 

[danbr]

What i'm trying to say simplified is:

The flow and return pipes are 22mm copper, when the pipe goes vertically through the internal wall to upstairs it has been reduced to 15mm. Should i increase back from 15mm to 22mm at the nearest point upstairs, or will this not make a difference as there is a section of 3metres in the flow and return that is 15mm.

 

[AGAS]

Running 15mm flow and return pipes for the 3 meters is completely adequate the only
differance would be price,
concerning the hot and cold, 22mm pipes would give you better/more flow to say shower and bath, so leave in 22mm as far as you can.
also leave the heating pipe in 15 mm, it won't make much differance looking at the distance to rads.
Cheers
paul

 

[danbr]

Thank you for your reply.

So running mostly 22mm for the shower and sink basin won't affect pressure too much? Also is it normal with a combi boiler that if the shower is running and then the kitchen hot tap is opened that the shower goes cold?

 

[slapper]

When you say "We went for a Combi", was that your decision ?

 

[danbr]

Yes it was my decision. Wanted as little space in the house taken up by water cylinders and plumbing pipes.