Supply pipes for Shower

[hawkeye]

I am installing a new shower (Aqualisa Axis Digital) that incorporates a small pump and requires 15mm supply pipes. I have received conflicting advice regarding hot water supply and would appreciate advice on the following:-

1) The simplest solution appears to be putting a branch in the HW vent pipe, close to the cylinder. This is 28mm so is it OK to fit a 28/28/15 tee?

2) Is is better to fit either a Surrey or Essex flange to take water direct from cylinder (although I can't see real benefit in doing so)?

3) Is there another option?

Many thanks

 

[ChrisR]

1) certainly not, it would suck air down the vent.
2) yes
3) not really. We see all sorts and sometimes it works better than others if a short cut is taken.

 

[namsag]

Most manufacturers recommend essex/surrey flanges as first choice. But also say if you tee into hot water draw off on top of cylinder providing you do it a minimum of 6 inches below the open vent tee it should work ok. And in the majority of cases it does. keep cylinder temp at 60c as temps above this can cause air bubbles to form in shower pump when working (cavitation)