Mixer tap not working

[sHighlander]

Hello to all DYIers and experts

I had separate taps in my bathroom for hot and cold water. I replaced them with mixer taps but it does not work as expected.

The reason is that cold water comes from the tank in the loft therefore there is difference between pressure/flow and mixer tap does not mix rather cold water is pushed back towards the tank.

I have Modena 80 e gas boiler and I set it to the lowest temperature setting, however it is still to hot for the kid at full flow. I am ok with it.

What options do I have to fix this problem?

I am thinking of calling gas boiler engineer to adjust hot water temperature so it can be used for shower at full flow.

Any suggestions will be greatly appreciated.

 

[footprints]

Two options fit a thermostatic shower mixer tap, or fit a TMV (thermostatic mixing valve) under the bath it blends the incoming water to limit the temprature.
Standard kit for care homes etc.

Lots around just one example here.

http://www.screwfix.com/p/franke-thermostatic-mixing-valve-22mm/47922

 

[sHighlander]

Thank you for prompt answer, I think I will go for tap, the only concern I have that both tank and bath are upstairs so there may not be enough pressure for the tap to work.

 

[mogget]

Make sure you get a tap that is suitable for low pressure supplies (not all are).

 

[sHighlander]

Thank you guys,much appreciated.

 

[stardanny]

Your cold feed need to be from main cold feed for mixer taps to work correct.

Reason is why your taps not working as should is because your boiler is combi and the hot water is high pressure and the cold feed from tank is low pressure. It will stop cold coming in even you turn on a little on hot water.

For the taps to work, the cold feed need to be from main cold water.

Thermostatic mixer need equal pressure to work correctly.

Daniel.

 

[sHighlander]

Well someone is wrong here, I ordered thermostatic mixer - that is another expense I went through and after that I did more reading and even asked questions on the site where ordered it in a chat room.

So hot water comes from combi and there should be 1 bar pressure. Both cold water tank and bath are on the top floor. there is not much elevation there max 1 m therefore wont't be more than 0.1 bar.

That is 10 times difference, should I be going through the trouble of fitting it only to find out it does not work.

I did read about other troubles that can happen when fitting thermostatic mixer with combi.

Is there ANY way to make this work or should I just give up?

Your input will be greatly appreciated, it would be nice when giving advice to cite if you have any hands on experience with these problems - I still appreciate everyone's input.

Thank you in advance.

P.S The following site states that thermostatic mixer can work on up to 10:1 pressure difference:

http://www.bathroom-association.org/pdf/Consumer Advice TMVs.pdf

I also have the option to reduce the flow of hot water by adjusting the valve in the kitchen. Just I don't know how much of shower would I have on the top floor.

 

[stardanny]

Really the cold feed should be from main water and storage tank removed when the combi was put in so all outlet have equal pressure.

You can try it but I doubt it will work correctly.

It is a easy job to change from tank fed to main fed is remove tank and run new pipe from main pipe that supply the tank to cold feed that came from tank.

Pressure bar, it could be 1 bar or 3 or 8 bars depend on your main water pressure. Mine is 8.5bars. How dou you assume it is 1 bar?

Daniel.

 

[sHighlander]

Just read somewhere and it may not be correct info. I have no skills to replace the tank so I would need to employ someone to do it. I did not know it is that easy.

What was the purpose of fitting the tank anyway if you don't mind answering.

 

[stardanny]

Possible there used to have a hot water cylinder fed by water tank in loft before being taken out and a combi fitted, changing from low pressure to high pressure hot water and the installer didn't bother to remove cold water tank. You might be able to see if there is 2 outlet from tank at bottom, one feed bathroom the other one is capped somewhere.

Daniel.

 

[sHighlander]

Well trying to send you PM but it does not work coz you only allow friends messages, may need some help with.