Low pressure to bathroom cold tap

[MD1180]

Hello,

I am quite new to this and have recently installed a thermostatic mixer tap to my bath, the hot pressure coming from the combi boiler is fine but the cold tap direct from the mains flows quite slow (it is on a 15mm pipe but then has been converted to 22mm - is this right, it seems to be defeating the object to convert the pipes up like that ??).

I assumed that this was caused by the ancient taps that were there previously as the cold tap would only turn half a turn and therefore not opening up properly.

However even with the thermostatic tap the temperature fluctuates quite badly (I assume due to the difference in flow) - I have lowered the pressure on the combi-boiler (well under 1) to try to match the pressure from the cold, this made it slightly better but still far from perfect.

The rest of the cold taps run off a different mains line and I have checked that the stopcock is fully open which it is.

Any help, advice or suggestions would be much appreciated.

 

[chr15]

Hello,

I am quite new to this and have recently installed a thermostatic mixer tap to my bath, the hot pressure coming from the combi boiler is fine but the cold tap direct from the mains flows quite slow (it is on a 15mm pipe but then has been converted to 22mm - is this right, it seems to be defeating the object to convert the pipes up like that ??).

I assumed that this was caused by the ancient taps that were there previously as the cold tap would only turn half a turn and therefore not opening up properly.

However even with the thermostatic tap the temperature fluctuates quite badly (I assume due to the difference in flow) - I have lowered the pressure on the combi-boiler (well under 1) to try to match the pressure from the cold, this made it slightly better but still far from perfect.

The rest of the cold taps run off a different mains line and I have checked that the stopcock is fully open which it is.

Any help, advice or suggestions would be much appreciated.

Are there isolation valves on the supplies to the mixer tap,and if so make sure the cold one is fully open.
What is the flow like coming from the cold tap on the basin?
Are you sure the cold supply is not coming from a storage cistern in the loft or elsewhere?
If the cold flow elsewhere is ok then it has to be a partial obstruction,or coming from a stored supply or the mixer valve is faulty.

 

[MD1180]

Thanks Chr15,

There are no isolating valves anywhere on the pipe that I can see.

The basin tap comes from a different mains pipe and is absoltely fine as is the kitchen taps (is it normal to have 2 different main pipes coming into the property ?) This pipe from what I can work out is only connected to the cistern and the cold bath tap.

I should have mentioned that the property is a ground floor converted victorian house.

I did think that the poor flow may be down to several people in the building running off the same main but there doesn't seem to be any fluctuation in the flow at different times of day which I would expect if other people are using their taps at the same time.

I will try to establish if this pipe goes up to a communal storage tank in the loft tonight - do you know if this is normal in a converted flat - it seems odd as I do not have access to it.

 

[chr15]

It is not unusual for a bathrooms cold water to be fed from a cold water storage cistern which is ok but if you are feeding a mixer valve or tap it is likely to cause problems because of the difference in pressures,you need to trace that cold feed and see if it goes back to a storage cistern.
Mixer valves work best with equal pressures.