Unvented below sink water heater- PRV drain

[4xpaws]

You want to use a 10 litre unvented heater to run a bathroom?

Dan you've miss read...Its to supply a sink in a 3rd floor bathroom. ie just the one hot tap. (The shower's electric)

The size of the incoming main has little bearing on what happens after the heater with regards the safety discharge.

To sum up what I originally asked... The size of the pipe going into the PRV, be it 15mm or 22mm, does not affect the size of the discharge pipe on the PRV outlet? The PRV supplied has 1/2" inlet & outlet.

I don't think you quite understand how all this works do you?

I realise the vent will need to carry scalding water and steam. I'm thinking if you can have vents in CH DW vented systems run in PEX, why not this vent too? From the beginning, I didn't know whether the spec of PEX pipe could deal with this installation. Hence my original question.

So a 3m run off is needed (slate roof, cast iron drain), although the tundish has to be visible. I guess positioned up in the loft isn't 'visible'. Or does visible mean not boxed in? Looks like a long run of 28mm to get it to a hopper it is then.

Thanks for everyone's help to date.

 

[Dan Robinson]

That's alright then... I thought for a moment you wanted to run a bath off it..

 

[Doctor Drivel]

DD the man doesn't need a thermal store;

The water heater is a 15 litre sink heater I believe. So a thermal store is out.