Hot water cylinder on a vented system 900mm high by 450mm diameter, direct version. manufacturer advises capacity 117 Ltr.
Trying to work out if a pump installed via a flange to the tank and giving say 12 Ltrs a minute at the shower. Assume 8 Ltrs per min is hot water and the rest made up from the cold rising main.
What is the real capacity of useful hot water from such a cylinder. I guess say 64 Ltrs so eight minutes shower at most.
Does this sound somewhat optimistic.
Eddie
I would have said it was better than that. I reckon that the actual water capacity of the cylinder should be nearer to 130 litres - even allowing for a raised bottom. Maybe the manufacturer's figure is for 'useable' capacity? [I'm assuming that you're right about it being a *direct* cylinder - with no heating coils inside.]
You shouldn't get too much mixing of the incoming cold water as it displaces hot water out of the top - but you may need to adjust the hot/cold balance a bit towards the end of the shower.
By using a flange which picks up its water (say) 200mm below the top of the cylinder, you are reducing the effective capacity by about 22% - but you should still have at least 100 litres available.
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