On Feb 12, 10:56 am, fred wrote:

Hi all...

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

I suppose the advantage with b) is that the pump is simpler (single) and so
may cost less, but the twin pump is a standard retrofit for those wishing
higher pressure so economies of scale may have eliminates the price
difference.

Good point, although the difference in costs between the two types
pumps is unlikely to sway the decision much either way as I'm doing
all the labour myself.

Bear in mind that with a) you can use the cheapest (pressure) grade of
cylinder available whereas with b) you may require a more expensive one,
plus grade 3 (lowest) cylinders are on the shelf in every plumbers'
merchants.

Now that is likely to be more of a cost differential. I do have to
get the combi made to order though as I need a short squat one.

Remember also that in a) there is no requirement for the hot and cold
tanks/cylinders to be co-located, the cold could be a coffin tank high up in
the apex of the roof or elsewhere.

Yeah, its probably easier to go with a combi cylinder though in my
particular scenario

Interestingly I rang Stuart Turner technical dept and they said that
even with option (b) you need some head over the pump (he said at
least 1m) to prevent cavitation, etc. So given that, I'm probably
almost definately going with option a. Until I change my mind
again. That has to be the worst bit about DIY, too many options!

Niall