Installation of new digital shower - hot water connection

[RHD]

I have always done my own plumbing but have stopped at installing new connections to the hot water cylinder. I have just moved to a new house and looking to install a new digital shower in an ensuite bathroom. Unfortunately my plumber has let me down. The system is gravity fed.

My question is what is the best method to connect this digital shower to the existing cylinder and pipework? The hot water cylinder outlet from the top is a ‘t’, although unsure if this incorporates a surrey flange. The first tee solely supplies the existing digital shower (Mira mixer/processor in loft) in the family bathroom, which has an expansion pipe into the loft tank. The second tee supplies the hot water to the remainder of house, including a twin pump for the old ensuite shower which I have removed as well as an expansion pipe into the loft tank.

The new digital shower (aqualisa) will be located in the loft, so to share the first tee with the family bathroom shower would be simple but this would not be a dedicated supply. Would this mean both showers could not be used at once? Would there be a danger of the shower pump not in use running dry? Would a non-return valve prevent this? Would this affect the flow?

Alternatively, would a spur 12” above the second tee directly from the expansion pipe – running off horizontally before going up in to the loft – be feasible? Would 12” below the tee be better?

Is an Essex flange perhaps the answer? I would rather not tackle this myself however. Can this be installed if a surrey/york flange is also present?

I have an electrician obviously installing the electrical connections required.

Any advice would be greatly appreciated.

Thanks
RHD

 

[Radioman]

Aqualisa are very specific on the supplies to a digital shower. Eg they must not be significantly affected by use of other outlets on the system (quote from installers handbook) so you would want a dedicated first draw on the hot and a separate supply from the cold storage tank to comply with warranty. Definitely no joint supply. Essex flange would work but you will lose the top section of hot water in the cylinder. A Surrey flange would also work. Minimum cold water capacity requirement is 50 gallons, maximum hot water supply temp is 65c. Avoid long pipe runs, processor must not be in frost risk area, must be accessible for service, if using plastic avoid lots of 90 deg elbows and use pipe inserts, make sure processor control cable can be removed after installation. It's a great product with a fantastic warranty.

 

[Unregistered]

Many thanks Radioman, very helpful. What constitutes a dedicated supply? As i already have an existing digital shower which has its own sole hot and cold supply, the other tee from the cylinder feeds the other taps in the house. Can you have 3 supplies coming from a single cylinder? If so, what is the best method? Would sharing a hot water supply with the taps in the house be sufficient or would that also invalidate the warranty. Thanks again.
RHD