Possible Airlock in cylinder coil

13 Aug 2019
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United Kingdom
Hi all,

I have an indirect heating system (boiler in kitchen, storage tank in spare room). Recently turned off the mains water and drained the hot water tank to change a tap in the bathroom. Since then we can't seem to get any hot water at all. The CH works fine but the coil IN pipe is sort of lukewarm and the coil return pipe is ice cold.

Does this sound like an airlock? any ideas on what i can do?


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Are we talking about 2 different things there. The Coil flow and return heats the water in the cylinder. The supply to the cylinder goes in the bottom of the cylinder and the hot water comes out the top.

Are you just getting water out of the hot taps, it's just that it's cold?

Draining the hot water cylinder to change a tap (didn't need to do that BTW) shouldn't have affected the central heating system water that runs through the coil to heat it up, they are 2 completely independent systems. If the water in the central heating system was drained/interrupted then air could have been introduced into the supply to the hot water coil. If not then look to the system control/valves.

If there is air in the system then there should be a bleed point on the pipe that comes out of the top of the coil, that needs opened to bleed the air out.
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Hi guys l have the same problem, change my taps in the bathroom and now no water coming out of the hot water taps, l though it maybe an airblock so l contact a flexi to the cold water and hot tap and turned it on to clear any air that maybe trapped, but l then checked the fortic cylinder tank though it maybe the ball valve and changed it the valve was okay the feed in the tank is not turning of and is filling up the cold water tank would this be a coil problem??

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