mixer shower for low pressure in flat?

diyplumber1980 · 20 Apr 2016

Hello, I would be grateful for some advice from those with experience working in high rise flats.

The tenant currently has a bath mixer tap in a flat 11 floors up. Its one of those mixers with a lever in the middle that you pull up to switch to the shower function. They have a tank system, and the cold water cistern is probably only about 80 centimeters above the hot water cylinder. Now when they pull up the lever on mixer tap, it drops down as the pressure does not seem enough to hold it up.

That tap will need to be changed but could someone advise on a suitable tap? Pressurr is probably around 0.1 bar on hot bath tap. Would a deck mounted thermostatic bar shower mixer do the job? I have seen a couple which say suitable for 0.1 bar pressure

Thanks in advance

dilalio · 20 Apr 2016

It's going to be rubbish without a pump! The only thing you can do is measure the flow and pressure and hunt for a suitable product!
But the higher you raise that shower head, the worse it will get!

Will.. · 20 Apr 2016

Electric shower off the mains is another option?

Madrab · 20 Apr 2016

If electric isn't an option then you will get LP 0.1bar mixer taps with shower attachment. You won't get the best shower from it but I guess that's what they had previously. If a deck mounted mixer says it will run on 0.1 bar then if it doesn't it goes back, simples.

Wonder why the pressure has dropped though if the lever won't work correctly now, unless their current tap needs serviced.

diyplumber1980 · 20 Apr 2016

Apparently the previous tenants used a bucket and jug to wash as the shower mixer tap was rubbish!

I may go ahead with the deck mounted thermostatic mixer tap, the tenant isnt too fussed about high pressure, he just wants to be able to shower. Will keep u guys posted on outcome.

copea · 20 Apr 2016

Clothes peg on the lever to keep it up.

diyplumber1980 · 27 Apr 2016

Hello

I purchased the 0.1bar deck mounted thermostatic mixer bar and fitted it today, sadly it only made a slight difference/improvement but not enough to be able to have a proper shower. I've added photos of the layout of the hot water cylinder and cistern, and the pipework under the bath.

I am thinking of getting a pump but not sure if i should get a twin impellor or single. The cold water pressure seems ok so I was thinking maybe just a pump fitted on the hot pipe under the bath may be sufficient?

Could someone please advise and I would be grateful if you could recommend a make and model?

Hello

Madrab · 27 Apr 2016

1st Issue, avoid using flexi pipes on a LP system, you want 22mm right to the tap.
Don't use PTFE on the threads of the connections, if fitting is weeping then replace the olives or if needed, wrap the olive not the fitting.

If you plan on a pump then you need to confirm that the bath is fed from the cylinder and the tank, then it's time to get rid of the tatties and pots. Twin impeller pump would live on the floor beside the cylinder, no more than a1.5bar pump (Stuart Turner) given the cold cistern size & some careful system planning required.

diyplumber1980 · 27 Apr 2016

Madrab thanks for the reply. Can i not fit a single impellor pump to the hot pipe going to the bath shower mixer?

Yes the cylinder is feeding the bath, the bath is directly on the other side of the wall to the cylinder.

Madrab · 28 Apr 2016

Is the cold water cistern feeding the bath too or is it on the mains? Yes you can just pump the hot though for a mixer to work correctly it really needs a balanced supply - hot and cold at the same pressure/flow. So you need to know what's feeding what to start with.

diyplumber1980 · 28 Apr 2016

i cant remember 100% but the pressure does seem quiet a bit higher so I think its coming off the mains.

If its coming of the mains can I fit the single impellor pump onto the hot pipe to the thermostatic mixer tap?

Madrab · 28 Apr 2016

You could yes but ideally you would find out what the cold pressure at the mixer is and try and match that with the pump output, it is a bit of a fudge though.

diyplumber1980 · 4 May 2016

Hi been looking into the pumps a bit more, and am a bit unsure over the positive and negative pressure issue. On the system im working on, the shower outlet will be about 50cm above the outlet from the cold water cistern to the hot water cylinder. It say online that a negative head pump is required, but what happens if i fit a positive head pump?

Madrab · 4 May 2016

If it's within a negative head area (little or no natural gravity flow at the shower head) the pump will not start. Positive pump requires flow to activate the switch, if that flow isn't present,then it's no switchy onny.

That being said, if there's access to the flow switch connections then they usually can be manually bypassed.

diyplumber1980 · 4 May 2016

I see. So in my scenerio what pump would you recommend? There is very little flow when the shower head is held about 1.5 meters of the ground

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mixer shower for low pressure in flat?

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