On Wed, 6 Oct 2004 00:40:02 +0100, "John Aston"
wrote:

Many thanks to Andy Hall and others for their help earlier this year on the
design of my new plumbing system (http://tinyurl.com/3pwck etc.).
Unfortunately, thanks to a few months illness, I'm still at it - with a few
issues to resolve.

A question regarding an unvented domestic hot water system: Cambridge Water
tested my incoming main supply and informed me that the pressure = 2.8 bar
and the flow rate = 25 litres per minute. Is this sufficiently high for an
unvented supply feeding a family home containing two power showers, a bath,
five sinks, three toilets, a washing machine and a dishwasher?

My feeling is that it isn't. At worst, I would guess that only one shower
and the bath would be running concurrently. Even so, a power shower consumes
15 lpm and a bath consumes 20 lpm.

I think that it's marginal. The static pressure is reasonable but
not exciting. Flow rate isn't brilliant but not at a level where the
supplier is likely to do anything for nothing.

You could put flow restrictors on the feeds to the bath to protect the
flow to the shower, and if you don't mind reasonable pressure but not
high shower flow, you could do the shame with the showers and perhaps
cut them to 10-12lpm.

At these levels I think I'd try to do something about it.


Is there any way around this problem? A pump and hydraulic accumulator
sounds expensive. Due to a loft conversion, there is not any convenient
space for a cistern, although I'm thinking that I may have to create some...

Don't forget that there are tanks available in different shapes and
sizes from Polytank and that one can always link more than one
together if it helps with the nature of the space available.

About the only other option is to look into having a larger diameter
service pipe installed from the road main into the house. THis can
be disruptive and not inexpensive of course.



[For information, the hot water will be heated indirectly in a 250 litre
tank by a condensing boiler. The mains supply pressure will be reduced (to 2
bar?) by a water softener, although a "high flow" softener, such as the
Kinetico 2020c HF, will be fitted to minimise this problem.]

Certainly a high flow type should be used..



Presumably the central heating could operate as a sealed system, even if the
hot water tank is vented?


Yes it can.



TIA



..andy

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