# Possible airlock in hot water cylinder ?



## Deejay100six (Nov 24, 2007)

Hi, :wave:

I have a somewhat dated hot water system consisting of a gas fed Baxi back boiler serving the central heating system and hot water storage in a dome topped copper tank. I also have an electric immersion heater in the tank.

My problem is that when the water is heated with only the electric immersion heater, the tank gets hot at the top but remains cold at the bottom leading me to believe that there is an airlock in the bottom of the tank which may have been caused by my draining the system off to remove a radiator at some time. The strange thing is, (and to me, this defies logic) that when I turn on the gas boiler so that the water is being heated by that and the immersion at the same time, the tank gets hot from top to bottom. 

Indeed, when my home was owned by the local authority (council), the service engineer demonstrated a way to remove such an airlock by removing the thermo coupling from the boiler allowing the boiler to actually boil. This seemed a little drastic to me but it has worked a couple of times in the past. Last time I tried it however, it didn't work and also I've noticed that the immersion heater elements only last around 12 months and the last but one that i replaced had corroded to such an extent that it had bent itself double ! I only just managed to get it out through the hole.

I'm hoping there are some plumbing guys here who might have one or two suggestions.

Thanks. :grin:


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## SABL (Jul 4, 2008)

I know very little about your heating system but evidence points to air in the system. The electric element in the top of the tank is not fully immersed in water and causing a short service life. How is the water replenished after loss of water due to maintenance??


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