Repeated airlocks?

Hi everyone, I'm hoping someone might be able to help me here....

I have a servowarm central heating system (elite 50 I think), cold water tank in the loft, hot water tank in the airing cupboard.

I have a recurring problem with airlocks in the hot water system when I come home after being away for a few days. I don't have a thermostat on my system so I tend to leave the heating on for a couple of hours each day when I'm away in the winter. When I come home, water runs through the hot taps at first then slows to a dribble. Each time I can sort the problem by turning on the hot water at the kitchen mixer tap and holding my hand over it while I turn on the cold tap. After doing this the hot water starts to flow again (and is usually very hot) albeit coughing quite a bit with air mixed in the water.

Can anyone help with why this keeps happening? My only guess is that the water in the hot water tank might be getting too hot, creating steam and therefore air in the tank, should there be some sort of cutoff to stop this happening though?

Happy to answer any other questions, this is my first post and I'm a plumbing novice (oh and I'm also a girl so be gentle )

Jen

Have you considered the possibility that you might have a dead animal partially obstructing the cold feed to your hot water cylinder?

No I hadn't, I take it that would be in the cold water tank so I'd need to get up there and have a look?

That could explain why it only happens when I go away, presumably whatever it is would settle and sink when the tank's not being filled cause the water's not being used...

It's only a revolting theory - worth a look and a pair of marigolds though.

Yep, definitely worth a look, thanks for the suggestion.