Water pressure problem, gravity tank + shower booster pump solution?

[laike]

I just bought an upper 2-floor maisonette flat and upon taking my first shower realised there is no cold water pressure from the shower head, only hot. The bath nozzle has some (weak) cold water pressure. Please see the attached diagram.

I think the explanation is that the gravity cold water tank in the airing cupboard (no loft access, it’s fully insulated and blocked off) is below the shower head, measurement ‘x’ in the diagram. This would explain why the bath gets some cold water as it’s below the tank, measurement ‘y’ in the diagram.
What is the best way to resolve this problem?

One solution I’ve designed is attached. I wonder if I piped the cold water tank down to the lower floor, into a shower booster pump, and back to the upper floor shower – would that give me additional cold water pressure? Notice it would have to pump beyond the height of the cold tank to reach the shower head, distance z + x. Would this mean I’d require a negative flow pump? If the height of x is about 1m, could a standard pump do the job?

Thanks for your help.

existing system:


proposed solution:

 

[Alanc]

Where does yor hot water come from, combi ?

 

[laike]

yes, hot water from combi boiler. But because this is the only water in the shower, the temperature has to be set very low at the boiler so that it's comfortable to shower in - as there's no mixing with cold at the shower! Really crap design, what a disappointment on day 1.

 

[SimonG]

Somebody was lazy when fitting the combi. Do away with the cold tank and hook it into the mains.

 

[Whyme]

Very strange to have a tank in the loft and a combi ?????? do as simonG says..

 

[laike]

Even if I hooked the mains cold to the shower - I'd get no additional pressure than what I have now, correct? The pressure is bare minimally acceptable as it is.

This is a 1960s built ex council flat, 3rd (top) floor.

 

[SimonG]

Even if I hooked the mains cold to the shower - I'd get no additional pressure than what I have now, correct? The pressure is bare minimally acceptable as it is.

This is a 1960s built ex council flat, 3rd (top) floor.

How do you work that out about the additional pressure. If you are saying you have poor mains cold water pressure then a combi should not have been fitted.

I think there is a little confusion over pressures. What you really need is somebody in to have a look at the problem and test your water pressure. It would work out cheaper than fitting a pump.

 

[laike]

mains cold pressure is not bad, good advice on testing it - i'll give it a go.

i was confused that as the combi is hooked to the mains to supply the shower, i didn't think adding the mains back to the shower would increase the pressure (since they're both mains fed!). but i think the combi probably doesn't provide full mains pressure as it needs some time to heat up the water, so combining the combi + mains cold should probably increase pressure.

yeah i'd like to get a plumber in but i posted the job and nobody responded! how do you hire a plumber in london that is of reputable quality?

 

[stevetheplumber]

where in london are you ?

 

[SimonG]

It's just that in your first picture you show the cold feed to the shower from the cold water tank in the loft.

 

[Reg Man]

Meassure your mains pressure and volume. Best solution as said previously; both hot and cold to the shower fed off the mains water. This is the only simple method of ensuring equal pressure to both feeds.

 

[laike]

where in london are you ?

dalston, east london. i see you're also east? i have a big job to be done, all that has been mentioned so far plus installing the pipes for central heating (floors are concrete, not sure how to run the pipes). also complete toilet room refurb.

It's just that in your first picture you show the cold feed to the shower from the cold water tank in the loft.

yes that is the case. i didn't realise that hooking the mains up to the shower would increase the pressure as the combi is mains fed. but i think i get it now.

Meassure your mains pressure and volume. Best solution as said previously; both hot and cold to the shower fed off the mains water. This is the only simple method of ensuring equal pressure to both feeds.

got it, will measure pressure and configure the pipes as you say. thanks all!

 

[Reg Man]

Your welcome.:winkiss:

 

[stevetheplumber]

pm me a phone number im that way saturday probably afternoon

 

[laike]

hi all, just a quick update - I measured the pressure at the washing machine point on the lower floor and it's got 1.4 bar. Not spectacular by any means but do you reckon it will be sufficient for the solution we've agreed? (removing tank and joining mains cold to shower)

had steve the plumber round and he reckons it'll prob be alright, tho a bit of a gamble

 

[Dotty]

Had steve the plumber round and he reckons it'll prob be alright, tho a bit of a gamble

Steve knows his stuff, I'd go with his advice.