[Emma]

Hi - can anyone help?
We've just had our water supply pipes (from mains to meter and from meter to stop-cock) changed from lead to 32mm blue poly pipe, in anticipation of fitting a heat bank/ thermal store.
For most of the day the flow has improved dramatically - although my plumber's flow-cup only goes up to 17 litres a minute, the flow is well over that and my rough tests of timing the filling of a 12 litre bucket make me think we now have around 30 litres a minute.
However, at peak times (particularly between 7 and 8 am - when we need it most) the flow dies down to around 15 to 16 litres a minute. Pressure also falls, from 4.75 bar for most of the day, to 3 bar at peak times.
What I need to know, is whether 15 litres a minute will be enough if we go for a mains pressure system like a heat bank. We have a big house, and once all our work is finished it will be three-storey with 5 bedrooms and three bathrooms (One shower room, one with shower over bath, and one with separate shower and bath). The likely peak needs are a shower, bath, washing machine and dishwasher all going at the same time.
We were thinking of going for a Gledhill Boilermate (probably Boilermate BMA225), with the heat bank positioned on the ground floor, in the utility room next to the boiler.
However, if the flow is not going to be good enough, I think we're going to have to put in a conventional system. We have a crappy combi boiler (Saunier Duval!) at the moment, which is on it's last legs. There is room for a couple of cold water end-to-end coffin tanks in the lower part of the attic (higher front part of the attic is being converted and will have a shower room, so we would need a negative head pump), and the hot water tank could go where the heat bank would have, but all the pipework will be an extra hassle.
Any thoughts, recommendations, preferences?

However, at peak times (particularly between 7 and 8 am - when we need
it most) the flow dies down to around 15 to 16 litres a minute.
Pressure also falls, from 4.75 bar for most of the day, to 3 bar at
peak times.

I'm intrigued that you can have 3 bar static, but only manage 15lpm through
32mm MDPE. Perhaps you are measuring at a particularly narrow bodied kitchen
mixer tap? Otherwise, the only explanation is that you've still got some
sort of restriction in the pipework, probably on the supplier's side.

Christian.

Christian McArdle wrote:

I'm intrigued that you can have 3 bar static, but only manage 15lpm through
32mm MDPE. Perhaps you are measuring at a particularly narrow bodied kitchen
mixer tap? Otherwise, the only explanation is that you've still got some
sort of restriction in the pipework, probably on the supplier's side.

In a quest for enlightenment (prior to purchasing a new boiler) I
checked the l/m in our bathroom.

We have 3 bar static, but the thermo-mixing shower gives a mere 14 l/min
as does the cold tap on the bath, but the hot & cold tap turned on
together give 21 l/min.


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[Emma]

Originally Posted by Christian McArdle

However, at peak times (particularly between 7 and 8 am - when we need
it most) the flow dies down to around 15 to 16 litres a minute.
Pressure also falls, from 4.75 bar for most of the day, to 3 bar at
peak times.

I'm intrigued that you can have 3 bar static, but only manage 15lpm through
32mm MDPE. Perhaps you are measuring at a particularly narrow bodied kitchen
mixer tap? Otherwise, the only explanation is that you've still got some
sort of restriction in the pipework, probably on the supplier's side.

Christian.

Thanks for that Christian
I am measuring at a kitchen mixer tap, which (apart from the washing machine pipe) is currently the only water outlet on the ground floor. There is also approx 6m to 8m of 15mm copper pipe between that tap and the end of the 32mm poly pipe. Should I get the flow cup back from my plumber and try measuring the first floor bathroom and sink taps? (there is probably less 15mm between them and the end of the 32mm pipe , but they are obviously one floor up). Also, another poster indicated that turning on both the hot and cold taps on the kitchen mixer might make a difference to the flow.

Many thanks
Emma