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Cold water keeps getting an air lock following cholorination of cold water tank

As part of landlord regulations I had to get cold water tank chlorinated. I used local recommended plumber. The tank was cleaned and had an air lock straight after which they fixed. 3 months later the cold water stopped - another air lock. The plumber came back out and fixed it. When they left the tenant advised the hot water was running cold when she returned home. The plumber claims air locks are a known issue following cleaning the cold water tank (which had not been mentioned previously). They also claimed the hot water was working (clearly I believe my tenant). The plumber says they will charge if they come out again and I should have the cold water connected to the mains to avoid the air lock issues. I now have to get another tradesman out to look at the hot water tank as water is still not hot. Any advice? Is the plumber correct? There have been no issues in past 5 years with water, only post cleaning of the tank.

1 Answer from a MyBuilder Plumber

Best Answer

When the CWST was cleaned debris could have gone down one of the feed pipes partially blocking the cold water supply to the outlets in the bathroom also slowing the cold feed to the hot water cylinder.
It depends also if the hot water supply is not as powerful as it used to be. If it is the same the flow should not be blocked.
You may still have a air lock in your cold pipework.
Best place to clear it from is either the bath or toilet due to them being low down on the system. Suggest using a wet vac/hoover to suck out the air. Works for me usually.
It could be coincidence the that the heating element in the immersion heater in your hot water cylinder has blown and will need replacing.
Hope that helps.


Answered 4th Apr 2019

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