Advice on pipe sizes to run to new shower?

[nick99]

I am trying to work out what size pipes to run to my new shower valve.

The existing balanced cold supply is in 15mm.
The existing hot supply is in 22mm.

The shower valve has 22mm connectors for the water supply (its a fancy thermostatic one with a divertor to provide fixed shower head and also a handset shower).

I just had a new heating system (system boiler and ariston unvented cylinder, no tanks in loft, all high pressure) fitted. Also I live in a high pressure water area.

Is it ok to just extend the existing pipes and connect them to the shower valve (with a 15>22mm adaptor in the case of the balanced cold)?

Or is it wrong to provide a shower valve with different 'volumes' (as in size of pipe) of supply in this way?

If so should I get the domestic hot down into 15mm pipe first too so it matches the bal. cold?

Cheers in advance for your help. Apologies if this is a dumb question, but I only want to do it once

 

[Softus]

Is it ok to just extend the existing pipes and connect them to the shower valve (with a 15>22mm adaptor in the case of the balanced cold)?

Yes, but I would point out that you can't have a "balanced cold", unless it's balance with something else; like the hot. Just a question of nomenclature - not a big deal.

Or is it wrong to provide a shower valve with different 'volumes' (as in size of pipe) of supply in this way?

Not wrong - different diameter is usually irrelevant - only flow rate is important.

If so should I get the domestic hot down into 15mm pipe first too so it matches the bal. cold?

No.

 

[nick99]

Great, thanks for your help.

 

[Softus]

Or is it wrong to provide a shower valve with different 'volumes' (as in size of pipe) of supply in this way?

Not wrong - different diameter is usually irrelevant - only flow rate is important.

I should really qualify the above answer.

The usual reason for the hot service being run in 22mm, where the cold is in 15mm, is that stored hot water has a more tortuous path than the cold, and the flow rate would be too low if 15mm were used.

Having said that, where 'tank' services are used, I would always run 22mm for both hot and cold.

In your case this is now academic since you have a mains pressure system.