Help possible airlock in hot water shower pump Salamander ct50.system

[Simon O]

Good evening everyone.

I am after some advice with regard to our hot water system before I call out a plumber if necessary.
So about 3 times since Easter we have had what looks an airlock.
I have done the trick with a mixer tap which seems to fix it eventually, usually left overnight.
I am trying to get to the bottom of why it has started happening.
So we have a standard hot water cylinder with 3 cold water tanks in the loft that feed both the cylinder and the shower pump Salamander ct50.
The cold water is fed into the bottom of the cylinder and the top of the cylinder feeds both the shower pump and the rest of the hot water system via a standard flange.
Not sure how air is getting into the system and how we can vent it as I can hear it in the taps at times.
I can provide diagrams if necessary.
looking to understand if it is an airlock and why it takes all night to clear and why this has started happening and what I need to do to fix permanently.
Many thanks
Simon

 

[Deleted member 120897]

Have you checked the float valve(s) of the cold water storage cisterns in the loft?

 

[Simon O]

Have you checked the float valve(s) of the cold water storage cisterns in the loft?

There are 3 tanks shoehorned into the loft space. The nearest tank is the one that fills and also I believe outputs to the shower pump. The furthest tank is the one I think fills the cylinder. No way of getting to this and I don’t believe it fills except through the other tanks in daisy chain.
We have noticed some air inside the hot water but never been a problem.

 

[Simon O]

so the mixer tap trick didn’t work overnight so not sure what to think at present.