What could be causing an airlock in hot water?

[Vondaz]

Hi

We bought an old house approx 20 months ago and have made no changes to pipes or tanks or cylinders etc. For the last 4 or 5 months we have been experiencing problems with no hot water in our shower caused we think by airlocks in the hot water taps (upstairs and downstairs).

We know how to cure the airlocks (feeding the cold mains into the open hot tap in the kitchen). But, the airlocks are a recurring problem - every day. And it is the cause that we are trying to uncover.

I have drawn (rather crudely) the set up in the loft. I have also included measurements, because I wonder if the problem might be water being drawn from the hot water cylinder faster than it can be replaced by the cold water storage tank (possibly due to the pump) thereby creating an airlock?

But if that was the case then it should've been a problem ever since we moved in and not something that has developed over time.

Alternatively, could the air be getting in from the cold water storage tank i.e. the water is being drawn from it faster than it can be replaced from the mains pipe? Could it be the ball cock in the cold water storage that is causing the problem?

Any thoughts would be appreciated.

 

[ecowarm]

I would say air is being drawn in to the system by the shower pump through the open vent.

Is the connection to the cylinder from the pump just "teed" in or is it a surrey flange Deva Pumps D-SF022 22mm Surrey Flange. - TrueRooms.com


Eco

 

[md68]

Got to agree. If it's just 'T' in then either get a surrey or essex flange fitted.
My personal preferance would be for the essex flange.

 

[Vondaz]

Hi thanks for the replies. The top of the pipes is a T rather than a surrey or essex flange. That said, the first thing we did (because it was easiest for an amateur like me) was the replace the ballcock in the cold water storage tank. The old ballcock was full of scale so it was due replacement.

This seems to have cured the airlock.

However, now we have water pouring out of the cold water storage tank's overflow pipe ONLY when the boiler is heating the hot water. I.e. it does not overflow when the boiler is not heating the hot water - so by association, the new ball cock should not be faulty(?).

Is it possible for the water in the hot water cylinder to push the feed from the cold water storage tank back up into the cold water storage tank - and thereby create the overflow?

 

[traineedrip]

you may have a hole in the hotwater cylinder coil. hot water leaking into the cylinder forces water up into the loft storage tank?

Is there a decent capacity in the cold storage tank? Showers can use loads and if the tank gets low it can drag air in.