Shower pump for hot only

[billplumb]

Maybe Chris, u have got a **** water supply an applys everywhere else, BUt unfortunatly thats not the case here

 

[billplumb]

and who are u to tell me to use the edit key Chris

MOD 2

he didn't i did

 

[kevplumb]

the cost of a electric supply or new 22mm supply to to pump plus the cost of the pump seems to balance the costs

if it does the spark is working for nix

why not just take a cold feed from the head tank

 

[corgiman]

but bill there is no way even the largest most power electric shower would give the performance of a thermostatic mixer and a pump!!!!!!

I think that you are wrong and the advise you have given is also wrong. but feel free to show me this electric shower as, if it exists, it will make a lot of my clients very happy

and chris was not commenting on costs and neither was masies dad they were talking about performance and whether pumping the hot water against the cold feed would be acceptable.. which I dont think it is and dont think it would work but chris seems to think it would be ok, and seeing some of his past posts I would be inclined to give it a go.

 

[billplumb]

obviously corgimann u have just agreed with me which makes it 2 to 1

 

[corgiman]

Stuart, you won't get much in the way of flow from an electric shower. Your original idea of pumping the hot only and mixing with mains cold, although not approved, will give much better performance.

I really wasnt agreeing with you bill I was agreeing with that ^

 

[billplumb]

This will not give you performance at all and nothing but trouble

 

[chrishutt]

....whether pumping the hot water against the cold feed would be acceptable.. which I dont think it is and dont think it would work but chris seems to think it would be ok...

Let me explain how I think it could work. Firstly let's say that we have mains pressure of 2 bar on the cold side, and on the hot side a tank fed supply boosted by a pump to give say 2 bar pressure. Result - a perfectly balanced set-up.

It makes no difference to the shower valve whether the water comes via a tank and pump or directly from the mains, providing the flows are adequate and the pressures are roughly balanced. In fact some shower manufacturers specify that hot and cold supply pressures can vary up to a ratio of 1:6, e.g. 5 metre head of hot and 3 bar cold!

Of course you have to consider the extent to which cold mains flows and pressures might be affected by other taps being operated, but a PRV could be fitted on the cold main to stabilise pressures. Also appropriate check valves should be used to comply with water regulations.

One proviso for the above set up is that when the shower valve is operated the initial hot flow is sufficient to trigger the flow switch on the pump. Since the initial unboosted hot flow would be competing against the cold mains pressure this cannot be assumed, but providing the mixing valve can restrict the cold flow enough the hot flow should be sufficient. A thermostatic mixer should do this automatically.

 

[corgiman]

thats good enough for me chris

also i suppose you can pop an adjustable PRV on the mains side and get it down to 2 or 1.8 bar couldnt you?

 

[chrishutt]

Yes, an adjustable PRV on the mains side would allow the pumped hot pressure to be perfectly matched, whatever it was (unless it exceeded the mains pressure!). The point is that all the shower valve "knows" is what pressure and flow is available at each inlet.

 

[kevplumb]

sounds good to me