I was thinking of changing to a pressurised system for our fully-pumped CH/DHW system, in place of the existing feed and expansion tank which I suspect doesn't give enough static head to prevent occasional air into the system.

The only problem is that our incoming water pressure is very low, I don't think it would be sufficient to charge up a pressurised system.

Are there other ways of providing the required initial pressure?

Thanks in advance, Tony S