Hi all...

I'm replacing the boiler and DHW system in my 3 bed semi-d that I'm
renovating.. so far so good - thanks to all the regular posters! I've
putting the boiler and DHW cylinder in the loft (attic) space to save
room downstairs. Hoisting the boiler up was fun!

Anyway, I've run into one issue which I haven't seen covered here
much. I live in Dublin, where the mains water supply / pressure can
be quite erratic, especially during summer. That pretty much rules
out a mains pressure system. The local water bye-laws also mandate
cold water storage for cisterns, showering, etc. I guess this is to
stop our mains distribution system getting overloaded at peak times.

So I can't get rid of tanks in the loft, and if I want a pressurised
(power) shower I'm going to have to use a pump. The two options seem
to be either (a) regular vented / unpressurised system where the pump
is on the appliance side of the DHW cylinder or (b) use a pump to
pressurise an unvented cylinder from a cold water storage tank.
These diagrams illustrate what I mean:

a - http://www.lycrisbyrne.com/images/combination1.jpg
b - http://www.lycrisbyrne.com/images/glasslined2.jpg

All the kit will be in the attic, so if I go with (a) I'll need to use
a combination cylinder to get a positive head to feed the cylinder.

Has anyone installed (b) the pumped unvented system?

As far as I can see the only pro is that I can have a larger DHW
cylinder as I don't need the cold water directly overhead, but with
the drawbacks that I will have pump noise on any hot water draw off,
no hot water if the pump fails, and more complicated pipework.
Advantage combi cylinder?

Thanks for any input...

Regards,
Niall