Persistent loss of cold water in bathroom washbasin

[Bob2153]

Hi All,
Would appreciate some advice. I have just had my cold water storage tank in the loft replaced and after 2 to 3 days I lose all pressure in the cold water supply to the mixer tap in the wash-hand basin. The plumber who did the job said it was an airlock and back-flushed the open cold connection using the supply from our power shower. After a day the flow began to diminish again and on day 3 it became a trickle only. Plumber returned and back-flushed again and the flow was reinstated but the same has happened again after 2 to 3 days but this time the is no cold water at all. He has recommended that we have additional work done by tapping into the cold water feed to supply the washbasin and toilet. All other cold water taps in the house are working OK and the problem is limited to the cold water supply to this one mixer tap. This is the first time I have had this problem and the back-flushing seems to only be a temporary solution as the pressure drops of over the next couple of days. The plumber says it is not related to anything he has done? Any suggestions as to what may be causing the problem and is his recommendation of connecting direct to the cold water feed the right thing to do? Appreciate any feedback.

 

[Chuck]

The plumber who did the job said it was an airlock.

Unlikely unless the pipe that feeds the problematic tap rises above the level that it leaves the tank at. This shouldn't be the case if the new tank was installed properly.

If that's not the problem, you've either got a faulty mixer tap or (less likely) a foreign object somewhere the pipe that is moving into a position where it's blocking the flow or interfering with the tap opening. Does the mixer tap valve feel 'normal' when you operate it?

A few photos of your pipework and new tank would be helpful.

 

[jtsplumbing]

Cold tap on hand basin should be on mains supply ! if not you could be cleaning your teeth with contaminated water be surprised what gets into roof tanks

 

[Bob2153]

Unlikely unless the pipe that feeds the problematic tap rises above the level that it leaves the tank at. This shouldn't be the case if the new tank was installed properly.

If that's not the problem, you've either got a faulty mixer tap or (less likely) a foreign object somewhere the pipe that is moving into a position where it's blocking the flow or interfering with the tap opening. Does the mixer tap valve feel 'normal' when you operate it?

A few photos of your pipework and new tank would be helpful.

 

[Bob2153]

The mixer tap feels normal. After it has been back flushed it flows good but starts to decline over time (2 to 3 days) until it becomes a trickle or stops altogether? Unfortunately the loft access has been resealed so it is not possible to get easy access to take some pictures. Could do that once the plumber returns. I just find it strange that the flow diminishes over time that would imply a gradual ingress of air if an airlock is causing the problem and back flushing does not cure the issue permanently. Has me baffled as to what could be the possible cause, especially with the loss being gradual and being limited to the one tap, everything was OK until the tank was fitted and the main supply turned on. It sounds from the other post that having the supply direct from the main supply would be advisable for health reasons? Was just trying to avoid the additional expense for the extra work if the root cause could be readily identified and fixed without the extra re-plumbing.

 

[Bob2153]

The mixer tap feels normal. After it has been back flushed it flows good but starts to decline over time (2 to 3 days) until it becomes a trickle or stops altogether? Unfortunately the loft access has been resealed so it is not possible to get easy access to take some pictures. Could do that once the plumber returns. I just find it strange that the flow diminishes over time that would imply a gradual ingress of air if an airlock is causing the problem and back flushing does not cure the issue permanently. Has me baffled as to what could be the possible cause, especially with the loss being gradual and being limited to the one tap, everything was OK until the tank was fitted and the main supply turned on. It sounds from the other post that having the supply direct from the main supply would be advisable for health reasons? Was just trying to avoid the additional expense for the extra work if the root cause could be readily identified and fixed without the extra re-plumbing.

 

[deg]

Repipe the mains to the cold tank supply in the roofs pace. Job done

 

[Bob2153]

Repipe the mains to the cold tank supply in the roofs pace. Job done

If I've understood correctly, to connect the mains directly to the tank supply line, does that mean I didn't need a replacement tank in the first place? My understanding was the tank is needed because it gravity feeds the hot water tank? Apologies for my ignorance.

 

[deg]

Yep you would need to keep the tank to feed your hot water cylinder. Changing your cold water to mains would save a lot of flapping about. As long as you don't have a mixer shower as this would give you different pressures and this would not be good.

 

[Bob2153]

Yep you would need to keep the tank to feed your hot water cylinder. Changing your cold water to mains would save a lot of flapping about. As long as you don't have a mixer shower as this would give you different pressures and this would not be good.

We do have a mixer shower that is supplied from a branch from the tank supply line? The plumber recommendation was to take two separate branches from the main supply line and connect to both the washbasin cold feed and the WC cistern feed. Would this be the best way to go? The existing feed to the Washbasin and the WC are branches of the main existing cold supply from the tank.