Air in water pipes

[Collywally]

I have always got air in mainly the hot side of the system
changed submersable pump twice already because they failed
However think its a problem on the truma boiler system does anyone had the same problem ?

 

[jumar]

Yes...been a problem for a while....thought I had cured it by fitting new pump, but it returns frequently...my submersible pump has a non return valve...I was told that, this is the culprit...however...the problem continues.