What do I do to sort radiators that need bled weekly?

[Swannykazoo]

This might be a Piglet john issue
Our house has 2 circuits for heating - one for upstairs, one for downstairs, and hot water completely separately. Its gas if that's helpful, built in the 70s. One radiator upstairs and one downstairs need bled weekly to stay hot as they just fill up with air. None of the others have anything significant in them. Its an L shaped house so I'm not sure how to bleed the radiators in order - which I've seen suggested on previous threads.
Presumably air is getting in somewhere, there's no evidence of water dripping/leaking out anywhere in the open. How on earth can this get fixed without someone taking up every carpet and floor to look for leaks?

Are the radiators that get air in them the closest to the boiler feed?
If it's that, it could be that the boiler is losing water pressure and drawing it out of the radiators
You'd need to top up the water, whilst bleeding the radiators
I'm just normal woman though :o

Downstairs - definitely not - unless the plumbing goes to the far away one first and has radiators in series after it. Upstairs - unlikely - as its across the hall and there is a bathroom and bedroom right above the boiler cupboard. I suppose I need to wait by the radiators as the heat comes on don't I to work this out! That would be great if that was the problem...ta!

I'm guessing it's an open vented system? (F&E tank in your loft which tops up the system)

You need a heating engineer to install a couple of Auto Air Vents on the system. These will automatically dispel the air and the system will top up from the f&e tank.

Brilliant! I will inspect at home today but that sounds much better than what I'd imagined