Hot water system plan

[Devisham]

Run the vent pipe to tundish - drain.
Make sure the CWSV overflow is screened.
Put a screened breather on the CWSV.
Consider TMNT/TMV to reduce scalding risk at outlets.
Remember check valves for backflow.
Consider localised pipework isolations to outlets/HWSV/POU to aid potential future works/repairs.
Consider HWSV destrat and/or HWS return pipework to aid HWS circulation.
Consider immersion min. DD HWSV instead of D HWSV.

 

[Knappers]

Lost me at 'DD HWSV'!?
But yea I like the idea of mains element min, think I'd loose the instantaneous htr as high maintenance and run mains immersion at say 40 with solar 'topping up'. Could drop mains supplied temp in summer and raise in winter.
You'll want atleast 22mm pipework for good flow (I'd go all the way to bath) and you'll get 0.1bar for every meter above outlet. Bear in mind that taps min working pressure is often the absolute min to get any water out so look for ones with 0.1/0.2bar min WP.
Also not sure how effective scale inhibitor would be in that position? I'd be inclined to put before instantaneous heater if you use one

 

[Learning Plumber]

Thank you Devisham, that's really useful detail. I'm going to google some of those acronyms now! I do my own maintainance work and it's always easier when the original install has been done with that in mind.

Run the vent pipe to tundish - drain.
Make sure the CWSV overflow is screened.
Put a screened breather on the CWSV.
Consider TMNT/TMV to reduce scalding risk at outlets.
Remember check valves for backflow.
Consider localised pipework isolations to outlets/HWSV/POU to aid potential future works/repairs.
Consider HWSV destrat and/or HWS return pipework to aid HWS circulation.
Consider immersion min. DD HWSV instead of D HWSV.

 

[Learning Plumber]

Thanks Knappers, I'll extend the 22mm runs. Had wondered about the scale inhib. position. Sounds like I might get away with a 3 metre height on the cistern with the right outlets - loft space won't allow much more and I don't fancy the headache of adding a pump. I went for the inst. htr option for flexibility, as there are low demand days, but a sealed complex unit like that does have obvious drawbacks.

 

[Learning Plumber]

I'll start updating my drawing and post back. Responses really appreciated.