no hot water from mixer tap and pump

[catnipsta]

I have recently installed a kitchen mixer tap (shower head type) and have not been able to get any hot water out of it.

I tried to solve the problem by installing a single pump (Contract Twin 50) to boost the hot water supply to the tap. Unfortuntately, it seems that the pump cannot be activated when the tap is connected - I think the low pressure drawn by the tap is too low. Without the tap's flexible tubing and turning on the flow at the isolation valve, the pump works fine.

Apart from getting a low pressure or perhaps a negative-head pump, what else can I do to resolve this problem?

many thanks in advance

 

[AdamW]

If you remove the pump, can you still get the hot tap to work by removing the flexible connector and just using the isolation valve? I suspect you will.

Did the hot water work work before you changed the tap? Did you make any changes to the pipework up to the flexible tap connector?

From what you have said it sounds like the problem rests squarely with the tap or its installation.

A different problem you need to address: A Contract Twin 50 is, as its name would suggest, a twin impeller pump. That is it boosts hot and cold supplies. You must not use it to boost just the hot using one side and leave the other side dry. And with your kitchen tap you should be using mains cold water (tanked cold water is not suitable for drinking) which must not be fed through the pump.

 

[catnipsta]

Yes AdamW, I get hot water from the just the isolation valve both with and without the pump. The flow is not great, however this was to be expected since I live in a flat, and the cold water tank is only at head height.

But as soon as I attach the flexible tap connector (not connected to the tap) the flow is reduced considerably...probably to be expected due to its smaller diameter ?? I tested the same tube with the cold mains supply, and works fine.

Once the flexible connector is connected to the mixer tap ( extendable shower head type) the flow stops completely from the tap.

The make and model of the pump shouldhave been New Pearl NP55, a single pump and not the Twin50 I mistakenly quoted..sorry.

with regard to the mains water flow back, I have installed a non-return check valve on the mains supply to the tap.

I thought of adding a negative-head unit to the pump, but some how I do not think that would increase the flow to activate the pump. Am I right ?

 

[oilman]

If the flexi pipe came with the tap, the problem sounds like it's the wrong tap and that you have a high pressure tap, whereas with your tank height you need a low pressure tap. You might be luckyenough to find a restrictor which you can remove, but otherwise it's another tap.

 

[catnipsta]

I have a feeling that even if I was able to locate and remove the restrictor within the tap itself, the problem will still exist, since the pump can not be activated once the flexi pipe is connected....even without the tap itself.

I guess oilman is right.....a new low pressure tap is needed.

 

[masona]

I guess oilman is right.....a new low pressure tap is needed.

Is there a way of telling the difference between low and high pressure tap by looking at it ?

I also have a poor flow tap mixer in the kitchen on the hot side.I looked under the floorboards and noticed 22mm pipe from the cylinder approx 2m then reduce to 15mm to the kitchen tap approx 9m run.What you lots reckon ? a new tap or have a 22mm pipe to replace the 15mm for better hot flow ?

 

[catnipsta]

I have finally rectified the problem...well not properly ...but at least I managed to get the pump to activate.

I changed the hot water flexi tubing to one of those copper version ( 15mm at one end and the other end is tapered to the same size as the flexi tube to screw into the tap). This allowed enough flow to activate the pump, but only when the tap's extendable hose end was about the same height as the tapered bit of the new connector. When the hose end is placed at its normal position in the sink, the flow gets reduced too low to activate the pump...BUT I am managing to get the pump activated by turning on the cold water for 2-3 seconds followed by a rapid turn to hot...I guess the syphon affect of the cold water draws enough of the hot water to activate the pump...problem solved...albeit it unconventional...but cheaper than than any other option I had planned.

Masona...if you also have flexi connectors I think you should also look into getting hold of these copper connector tubing them....I guess maybe it is because the tube is tapered which minimises the flow reducing affect.