Why not just use foam rope?

[hzz]

I have the same setup as you. I never blow the main drain line out. I just put the foam rope into it and then cap it off.

I lower the pool level to just below the return jets. Never had a problem yet here in Toronto.

[cbridges]

Thanks for the confirmation. Just can't understand why more people don't do this!

[Poconos]

I guess being able to use the rope would depend on the plumbing configuration. Access, bends, etc. If I had a main drain you could bet I would have access to the pipe where it goes straight to the drain.
Al