Yup had a large receiver and inline filter in the line, by air leaks I meant minimum that we could find, the pump was really working hard. The new project is in a mould with very flat surfaces to seal and I think we could almost get to the stage where there is no leaks( if that is really possible ) And I worry that we may almost lock the pump hence my question of introducing some form of electrics to control the pump.

Thanks for advice though and I will look up your recommendations