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Sosh 04-15-2005 10:56 AM

Hot water boosting shower pump

I'm from the UK, and this seems to be a US based forum, but hopefully our plumbing methods are simlar.

I want to install a shower downstairs. Problem is our cold water is directly fed from the mains, wheras the hot is vented and gravity-fed from a tank in the atic. I think that if I fit a mixer I will have problems with pressure differences. I know you can get pressure equalisers, but these take the higest presssure of the two down to the level of the other. Our hot water pressure isn't that great, so I don't really want to do this if possible. Has anyone come across a device that uses the mains pressure of the cold to force the hot through (bit like a car turbo), euqualising the pressure, but taking advantage of the high mains pressure? I've heard rumours about something like that, but can't find anthting.

Any info appreciated.


Teetorbilt 04-15-2005 08:37 PM

Must be Euro. I have never heard of a split system as you describe or understand a reason for it. Why the 'open' hot water heater?
I can certainly understand the problem.

Sosh 04-16-2005 05:12 AM

Hi Teetorbilt,

Most older houses in the uk have both the hot and cold gravity fed. I think there are a few advantages over a closed/mains fed system: You get a least some water during a mains failure, they are quieter than direct mains systems because of the lower pressure, and there's less chance of contamination through back-syphoning. Main downside is lower pressure.

Most newly built houses now are using mains for both hot and cold. Probably due in part to the availability of non-return check valves, and partly the lack of loft space in new houses (no room for tank).

Unfortunately we have a mixure of the two, so have a problem with different pressures. I take it the US mostly uses closed systems then? If so probably no one has needed to come up with a solution to this problem. Thanks for your help anyway.

Teetorbilt 04-17-2005 09:52 PM

Most homes here are on closed systems.
In answer to your problem; you need to find your 'end use flow' which means the amount of water that can flow through all of the hot water faucets/heads in typical use. Here, typical flow for a showerhead is 1.5 - 3 gallons per minute@50 PSI. The booster pump that you choose should closely match the PSI of your cold water system, go a bit higher if there is any question. You will have to determine the amount of flow.
Let's say that you are conservative and have 1.5 GPM showerheads. If you want to take one shower at a time, you can get by with a pump that puts out 1.5GPM@50PSI. However, if the missus decides to do dishes using the old 5GPM tap, your shower is going to get pretty cold.
With a 10 GPM pump, you can run 2 1.5 showerheads plus the 5GPM sink faucet.

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