Pipe diameter and isolating valves for combi shower

[chrispy33]

Hi, will be installing a shower next week and will be using a thermostatic mixer(combi compatible) which has 15mm inlets for hot and cold.

I presume that I'll be ok using 15mm pipe throughout to plumb this in but someone advised me that I must use 22mm pipe as per bath or flow will be poor.

If this is the case, do i need to use 22mm pipe and then fit reducers at the mixer? Can't see that this would make any difference though. From what i can gather, 22mm is necessary when using a gravity fed system.

Also, i presume that it is a good idea to fit isolating valves on the hot and cold supply to the shower. Is it best to use inline or gate type valves?

Many thanks, Chris.

 

[John506]

These will do.

15mm will be fine.

 

[slowboatshanghai]

A straight 15mm for both hot and cold feed is sufficient. Combi boiler should provide adequate pressure. Be selective with your shower head. Some shower head specify higher bpi.
Shut off/isolation is a good option on both feed. This will make any maintenance work a lot easier. In-line value will do the job.

 

[Adrian80]

Depending on your water pressure or flow rate, you might want to think about paying extra for full bore isolators. cost a couple of quid for 15mm ones. opposed to 69p

 

[chrispy33]

Thanks for your advice everyone Did notice the full bore isolators in the screwfix catalogue so will use those.
Cheers
Chris

 

[gas4you]

These will do.

15mm will be fine.

These only give about 6-8mm bore through them when open