Questions about putting a pump on a gravity feed hot water supply

14 Jan 2010
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United Kingdom
I need to change a bath mixer tap to a bath mixer tap with a shower hose attachment to make a shower that runs off the mixer taps.
The house has Mains cold water and gravity feed hot water. The house is electric only and it has a Direct economy 7 immersion Hot water tank (with the cold water feed tank sitting directly on top of the hot tank)
The Hot water tank sits on the floor of the airing cupboard, same floor as the Bathroom.
The house belongs to a housing association and I'm waiting for permission to carry out the alterations.
As the shower hose attachment would be slightly higher then the top of the cold water feed tank do I need a negative head Pump, or because the mixer taps are below the cold feed tank should it be a Positive Pump?
I really don't want to put a Essex or surrey flange on the tank just in case I damage their property, can anyone recommend a Pump that doesn't require these fittings as part of Manufactures fitting guide?
Was hoping fitting a pump to the gravity feed hot water would also increase flow to Kitchen sink hot and bathroom sink hot too?
Many thanks for reading
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Fitting a surrey or warwix flange is straightforward and tightens into the normal top tapping, so shouldn't cause any damage with that and is best practice as far as putting a pump on the hot supply is concerned. Only an essex is where you need to cut into the cylinder. You can use the pump to feed the whole hot water circuit but I'd recommend you fit a high quality, brass impeller'd, continuously rated pump if you're using it beyond just pumping the shower.

If the shower head, in normal use, will be in line with or above the cold supply cistern then you'll need a universal (negative) pump. You will also need to balance the cold mains feed in line with the pump output pressure.
Thanks for the reply.
When you say balance the cold mains do you mean just at the shower mixer taps or at the main stopcock? As for Pump, any recommendations? It is a One bed house with only one person living there, upstairs Bath, sink and toilet and downstairs kitchen sink that has a mixer tap on it. No Boiler, all electric.
Something I forgot to mention is the mixer taps with shower attachment will just be a normal set, they will not have a thermostatic mixer valve, does mains still need to be equal pressure?
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You would look to balance the supplies only to avoid any issues with backflow or resistance, especially if you plan to pump every hot outlet. pretty straighforward, just add a Pressure reducing valve to the incoming mains and roughly match the incoming pressure to the output of the pump.

Stuart Turner all day long. One of the monsoon variants are the best IMO, not cheap though.
About the negative/positive head situation. Yes the shower head running off a hose from the bath mixer taps would be level or slightly higher then the cold tank feed but mixer taps would be about a meter below. As there seems to be a big difference in Pump price between Positive and negative would the shower head work OK with a positive pump if the mixer taps was opened and set to correct temperature first then plunger opened on taps that sends water to shower head?
Also I have uploaded photos of the cylinder, it is a direct cylinder with the 2 immersion heaters in for day and night rate. I see the mains cold water going to the top tank and the hot water coming out near the top side of the bottom tank, I can also see the white overflow coming out of the top tank. There is another pipe opposite side that in covered the thermo molded jacket that I presume is the cold supply from the top tank to the bottom cylinder.
What seems strange to me is that the hot pipe doesn't have an expansion (vent) pipe going back up to the top cold tank, is that normal?
Also as you can see from the photo the hot pipe outlet on the cylinder looks like it will be a real pain to try and put a surrey flange on because it is a bit hard to get to, and as there is no vent pipe how would a surrey flange work?


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Hey ho... I started a thread about them myself...

Came across this product whilst looking for something else on Google the other day...

I remember seeing the inventor on Dragons Den. I don't think it went to well but I don't trust contrived TV productions personally, I know how they work!
The product looks good and the science behind it is feasible in my limited understanding!

Has anyone on here ever fitted one for themselves and or a customer?

If so, any good? Did you start specifying them to further customers? Would you?

I'm intrigued but would want to get one on trial and test it out on a family Guinea pig first (n)

FFS how do I link to an old thread?
Many thanks for replies, I will look into this pump.
What about the No expansion/vent pipe, is that Normal?
Any expansion in a combination cylinder would normally be handled internally by the feed pipe. There would also usually be an incorporated internal vent pipe.
Any expansion in a combination cylinder would normally be handled internally by the feed pipe. There would also usually be an incorporated internal vent pipe.
If it has an internal vent pipe does that mean I could connect a pump to the hot outlet feed without needing a surrey flange?
The standard feed would normally be below the top of combination cylinder. The only issue is that ideally you want to give the pump it's own dedicated feed to avoid any other hot outlet opening and reducing the flow to the pump. With a cylinder that you cant access or it doesn't have a top tapping then an essex flange would normally be fitted.

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