Air in returns only when using solar heater

[geepur]

I am getting a lot of air in the returns, but only when pumping through a roof mounted solar heater, which is on the outlet side of the filter. No bubbles at all when pumping direct with no solar.
Can't detect leaks anywhere.

[sleepless]

I reciently seem to get a constant bubbling noise in my roof when using the roof mounted solar heating. Any ideas?

[ninpoolman]

Listen to the pipes going up and down to the roof. If you hear more noisefrom the pipe coming down then your trouble is that the water is coming down faster than it is going up and it is grabbing air from the air relief valve at the solar panels. If this is a new problem it might be that you need to clean the filter and or baskets to restore the flow up the roof to match the flow coming off the roof. You may have a ball valve on the down pipe and if you very slowly turn it towards the off position just enough to slow the water coming down or building just enough back pressure to slow it so it stops grabbing extra air from the air bleed at the top of the panels.
Barry