increasing hot water pressure to kitchen taps

Hi guys, I have a gravity fed hot water system from a normal hot tank ch in the upstairs bedroom (a long way away from the kitchen tap) and the hot water takes ages to run, what's more is there is not enough pressure to let the new spray tap work properly. Cold water is not a problem.
can I fit a small pump to increase the hot water pressure?
If so where should I put it? I have two sinks one in the utility room (ie the old kitchen) and one in my lovely new kitchen in the extension.
The hot water stop valve turns all hot water to taps off, so if I put it near there it would increase the pressure all round.
Are there any items I should be wary of with the increase in pressure ie hot feed to washing machine, hot tank bulging? CH hot water system becoming upset?
what pump could I actually use?
thoughts and advice please,
(or could I get a spray tap which works better with low pressure hot water?)
thanks in advance dedics
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The pump would be between the tank and the taps, most likely near the valve you mention. It won't cause problems behind it and will only come on when water is called for. It will be fiddly to fit and a potential surce of leaks and breakdown and will be noisy. OTOH you'll get pressure!
A good make and something which would (probably) be quieter than the usual shower pumps might be:
http://www.inspiredheating.co.uk/acatalog/GRUNDFOS_HOME_BOOSTER.html
The fact that the "new spray" tap doesn't work indicates to me it is a pressure problem in taps designed for high pressure operation, rather than a flow problem. Were it just a flow problem and were all the piping done in 15mm, you might improve things by going to 22mm - if you do that, remember that the volume goes with the square of the radius (or diameter) of the pipe but the flow rate goes with some power less than this. This means you get more flow but it takes longer to run hot.
HTH
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Bob Mannix
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Please note - although this looks like a central heating pump (and, in fact, is one with some bits added) it is very likely that it MUST be mounted as the picture shows, or the flow sensor won't work (actual central heating pumps can be mounted anyway round, as long as the motor shaft is horizontal). This may make a difference to the ease of fitting!
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Bob Mannix wrote:

ok thanks for that, so it's the same size and shape as CH pump, I'll have to see if I can actually find space to fit one.
I was hoping there would be a smaller sized solution more the size of a washing machine pump.
dedics
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That was one example, there may be other shapes but not many smaller IMHO. Clealry this one is made by a central heating pump manufacturer so they have modified what they have. It won't give a huge pressure but probably good enough but should be quieter!

Well you might get a small one but it's unlikely to last as long. Your choice!
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Ian & Hilda Dedic wrote:

Basic physics is your foe here Ian, a washing machine pump really doesn't develop much head, and it would probably end in tears if you gave one such a task.
Compared with the expensive engineering from Monsoon, which purrs quietly in my garage to supply bath and shower, this Grundfos is tiny and cheap.
Does your tap have a pull-out spray, or simply a spray nozzle? I guess even if you can find a new tap, it could easily cost more than the suggested pump.
Chris
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Chris J Dixon wrote:

it is a new tap, that seems to be the problem....
it's a franke pull out spray jobby....
we only really need a bit of a boost in hot pressure to this one tap, the other mixers in the house seem fine so I wonder if looking at the inner workings might be a possible way to go.
tap experts anyone?
(Definition of an expert:-)
an unknown quantity under a lot of pressure!) dedics
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Ian & Hilda Dedic wrote:

I had the same problem, after buying an Ikea pull out spray type, which is probably the most unsuitable tap possible for a low pressure hot water system! I bought the Grundfos home booster pump, and while not perfect, it was a better solution than buying a new tap as I had already fitted it to the sink!
Without the pump fitted, although the hot would run (very slowly), any amount of mixing with the cold forced cold water backup the hot pipe and back into the hot water cylinder. This is because of the pullout spray nozzle meaning the mixing is done within the tap body rather than having separate hot and cold channels exiting at the end of the tap. So, in addition to the pump I fitted a single check valve to the hot pipe under the sink. This was not without problems though, as this restricted the flow too much so the pump did not trigger automatically! I removed the return spring from the valve, and all is well.
The pump is totally silent in use, the only problem is that when you want to run the hot, or mix with cold, it works best if you switch on the hot to full until the pump comes on, then close down the flow and/or mix as necessary. Luckily when I fitted the kitchen I installed mains sockets in the back of every cupboard just for this type of eventuality, and so I installed the pump in the cupboard under the sink.
Cheers, Ben
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In an earlier contribution to this discussion,

I assume that the cold comes straight off the mains, and so is at mains pressure.

Yes.
It depends where the stop valve is! If it's between the cold header tank and the hot cylinder (as is often the case) *don't* put it there 'cos it will pressurise the hot cylinder, which is *very* bad.

Put it close to the hot cylinder's hot *output* - then it won't pressurise the cylinder but will boost *all* hot taps. It won't upset the primary circuit used by the CH and by the coil inside the HW cylinder. It shouldn't upset the washing machine - but you may have swap a low-pressure inlet nozzle with a high pressure one. Read the washing machine manual!

You need a pump designed for this purpose - with a built-in flow-switch so as to turn on as soon as you open a tap. It probably needs bronze internals since it is dealing with constantly changing oxygenated water - unlike a central heating pump which is simply circulating the *same* water (hopefully containing corrosion inhibitor) all the time.
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Cheers,
Roger
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