DIYbanter - View Single Post - low pressure problem

wrote:

Doctor Drivel wrote:

"Roger Mills (aka Set Square)" wrote in message
...

In an earlier contribution to this discussion,
Stevethefootycoach wrote:

This sounds like a good idea.

Is it just a case of fitting a single impeller pump in line with the hot
water cylinder outlet? That would (presumably) boost the hot water
pressure to all taps in the house. Or should I fit the pump in line with
the feed to the bath/shower?

This is an alternative to the twin-impellor pump which I suggested
earlier, and involves less plumbing, but doesn't give equal hot and cold
pressures - which may or may not matter.

If you read and understood Christian's post this would all be clear. Using
one in-line pump on the DHW draw-off of a low pressure cylinder and the cold
to all taps via the mains can give equal pressure at the taps for mixing.
You install a 22mm pressure equalising valve after the pump, then both hot
and cold lines are at equal pressure. You could fit a few 15mm equalisation
valves on a few lines rather than a 22mm valve.

Assume: the pump gives out 1 bar, the mains 2.5 bar. When you turn on the
cold tap 2.5 bar is there. Then you turn on the hot and the cold drops to
the same pressure as the hot that is flowing through the equalisation valve.
If someone flushes a toilet and the cold mains pressure does not drop below
1 bar, then no affect.

The idea is not to have an adverse effect on the shower mixer, the most
critical part of the water system. If a separate shower en-suite shower and
someone turns on a bath tap then the pressure is going to drop along the
pumped DHW line. It mat be best to take the bath from the top of the
cylinder and the rest of the taps and shower from a Surrey flange. Then the
bath will not affect the pumped supply. If the bath water from the mains
then fix a low pressure hot water mixer on the bath

As far as location is concerned, you can choose how many of the hot taps
you wish to boost, and put it in an appropriate place to achieve this. The
pump will probably be heard throughout the house - which may be a
consideration.

The Grundfos single impeller Booster pump is quiet, and cheap (about £80)
its selling point.

[The normal way in which these pumps work is that they have a flow switch,
which detects (gravity) flow when you open a tap, and switches on the
pump. When you close the tap, the flow stops and the pump is automatically
switched off].

Thanks for that IMM and Christian. This Grundfos pump sounds a god
alternative to a big power shower pump. Another post to be saved.

What for? Half the information is totally wrong.

Regards
Capitol