On Wed, 06 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.

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...

[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.]

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

Given that you want to soften the water I strongly think that a pumped
storage cistern approach will be best. I'm really surprised that 2.8 bar
static on 32mm (25mm inside) MDPE pipe gives only 25lpm.
This implies that the supply in the road is somewhat restrictive. Did the
Water Company section in the road get replaced all the way to the main? or
just to the meter? or just to the property boundary.

How was the 25 lpm derived?


The are all sorts of tanks for using the eaves and apex of roof spaces if
that is an issue.

--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html