High 0r Low pressure taps?

[PeedOftec]

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Ok, I think I have an issue with a new basin taps that were recently installed.

The tap has a really low flow rate on the hot but the cold flow rate is ok.

The other point is that the tap is a mixer tap and when put half and half it appears to mix ok but switching back to HOT the tap runs COLD WATER.
There is a DHW loop that feeds the hot which is fed from an open vent cylinder. (therefore header tank pressure)

(don't know if the cold is forcing back along the hot pipe, but then it wouldn't be mixing on half half surely? Or is it the coldness of the taps metal cooling the hot water, but it is cold mains cold and runs cold for some time. The leg from the DHW loop is about 10m!)

The cold is fed directly from the mains.

Question.... on a mixer tap do you go for high or low pressure taps when the hot is on gravity and the cold on mains.... or are mixers out of the question?
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[JohnD]

if you have a mixer tap, you should not supply it with high-pressure (mains) cold and low pressure (tank) hot

If you do, it is pretty well impossible to control the mixed temperature

Consider fitting separate taps, or providing a new cold water pipe from the tank. It is possible to get a pressure-reducing valve you could put on the cold pipe, for £30 or so, but I am not convinced they are all that good. I have one on my guest-room shower, and it sometimes jams closed.

Mixer taps (especially one-hole ones) usually have small pipes and waterways and do not deliver much water at UK low pressures. They work much better in Italy where a lot of them come from.

 

[PeedOftec]

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Mmmm... the tap is a single hole lever mixer, monobloc I think....

http://www.gwsupplies.co.uk/bathrooms/p/6892/hansgrohe+talis+e+basin+mixer.htm

The model is a Hansgrohe Talis E2 with pop-up lever. After looking on the 'net it appears the taps are available in high and low pressure ones but I'm not sure which the plumber installed.
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[JohnD]

if you have a mixer tap, you should not supply it with high-pressure (mains) cold and low pressure (tank) hot

If you do, it is pretty well impossible to control the mixed temperature

still true.

BTW as you have a pop-up waste, it will in time leak

sorry.

Fashions vs. function.

 

[PeedOftec]

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if you have a mixer tap, you should not supply it with high-pressure (mains) cold and low pressure (tank) hot

If you do, it is pretty well impossible to control the mixed temperature

still true.

BTW as you have a pop-up waste, it will in time leak

sorry.

Fashions vs. function.

Dooh... The shop we got the wetroom fittings from is sending something through for the fitter to fit. Apparently it should have been fitted in the first place??

Will keep you posted.
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[dextrous]

Presumably a pressure reducing valve - may improve the situation.

 

[PeedOftec]

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BTW as you have a pop-up waste, it will in time leak

sorry.

Fashions vs. function.

Typical eh, the taps that were installed when the place was built in 1965 are still working fine, maybe the odd washer change...costing pence..... and the plug works fine, maybe that has been changed once in a while... again pence...

Fashion victims.....I hate it!
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[PeedOftec]

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Ok, the shop sent a different aerator for the mixer tap...... somehow I don't think this will resolve the issue, do you?

Incidentally, I was going to fit the aerator myself but when I unscrewed the existing "high pressure" aerator I found the filter behind it was clogged with all sorts of rubbish, scale, filings, etc... I left it on the side for the plumber to see when he comes to fit the new aerator..

I also downloaded the installation instructions for the taps and it states in there that the hot and cold pressures must be equal.. among other requirements.
See instructions below:-

Important! The fitting must be installed, flushed
and tested after the valid norms!
Assembly
1. Flush through the supply pipes.
2. Place the mixer including the sealing washer
in position on the basin.
3. Slide the fixation piece including the washer
over the threaded pins and tighten the nuts.
4. Connect the supply pipes to the isolation
valves; cold right - hot left.
5. 31612000/31613000/31622000
Connect the pull rod to the pop-up waste.
The hot and cold supplies must be of equal
pressures.
Operation
The mixer is activated by lifting the lever handle.
Turning to the left = warmer water,
turning to the right = cooler water.
Technical Data
This mixer series-produced with EcoSmart®
(flow limiter).
Rate of flow with EcoSmart:
7l /min 0,3 MPa
Rate of flow without EcoSmart:
12l/min 0,3 MPa
Operating pressure: max. 1 MPa
Recommended operating pressure:0,1 – 0,5 MPa
Test pressure: 1,6 MPa
(1 MPa = 10 bar = 147 PSI)
Hot water temperature: max. 80° C
Recommended hot water temp.: 65° C
If the continuous water heater causes any
problems or there is not enough flow of water, the
EcoSmart® (5a) located behind the aerator must
be removed.
To adjust the hot water limiter on single lever
mixers, please see page 8.
No adjustment is necessary when using a
continuous flow water heater.
Spare parts (see page 2)
1 handle 31692000
1.1 screw cover 96338000
2 flange 97406000
3 nut 97209000
4 cartridge cpl. 92730000
5 aerator 13912000
6 pull rod 96657000
7 fixing set 96016000
8 connection hose 3/8“ 97206000
9 connection hose Ø 10 96321000
Special accessories
X special tool set 58085000
(order as an extra)
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