Low flow rate - Combi boiler?

selc_83

Hi there,

I am doing some renovations to my house including putting in central heating and moving the bathroom upstairs. We have had some people round to quote who expressed concerns that our water pressure may not be good enough for a combi boiler.

We therefore had the water company out who said the the pressure was within legal limits of what they had to supply but the flow rate is a bit low. They also said that it is only us who is having the problem and the water pressure is good at the mains stop tap and therefore it may be a problem with our supply pipes which are on our land and therefore our problem. However, he also said that we 'may' share supply with our neighbour and they could share the costs of installing our own supply (i.e. they pay for the stuff out in the road and we pay for the pipework up to the house).

Shouldn't they know if I share I water supply or not?
Does anyone know what pressure/flow rate is ok to have a combi boiler with?
Would it be more expensive to pay to our half of the work for a new water supply or pay the extra £700 or so to have a tank system put up in the loft?

I am confused as to what to do for the best.

Thank you for any help.

gas4you

You ideally need a minimum of around 12 l/m cold mains flow rate for even the lowest powered combi that will give about 10 l/m hot water output.

You could replace the pipe from your external stop tap to the internal one. This will need to be at least 25mm these days, larger if you can afford it.

You could dig the trench etc and lay the alcathene pipe yourself, then get the water board to connect it up.

The water mains needs to be a minimum of 750mm below the surface.

PasturesNew

I had low flow rate, how this manifested itself for me was that if I went to the loo I had to wash my hands before I flushed ... or wait until the cistern had flushed before I could get any water out of the taps.

I had a combi and the measure came out at 12 litres/m when the little man measured.

The little man said to me 24-30 would be a good figure to aim for.

I was going to replace the pipe from my meter to my house, but never got round to getting quotes. It was "just me" so I lived with it. Most of the work is digging the trench, technical bit is changing the pipe. Then there's filling the trench in.

roger196

You need one of these to measure the pressure at the tap www.screwfix.com part no 82412. It fits onto washing machine tap. A vaillant combi needs mains water pressure of 1 bar for max flow rate. Minimum flow rate of 2.7 litres/minute at a pressure of 0.3 bar. It is likely these figures will vary for different makes/models of boiler so check the manufacturers instructions ( about 50 pages download from their website). Water flow meter (weir gauge) is at www.bes.co.uk part no 11491 and and water pressure gauge is part no 11711
Ask you neighbours if you can check their water pressure. If much different to yours you know you've got the problem. To check shared supply, turn off supply in road and see who does not get water....MUST Confirm with neighbours that OK to do so. You will need a stopcock key screwfix 71652.