We've just bought a 50-year old home with baseboard hot water heating. I know how to bleed pipes and radiators to release air blocks, but I can't find any bleeder valves in the "usual" places at either end of the copper pipes.

Sounds silly, I know...

Would they be located anywhere else along the pipes? Below the floor? Is there another way to get air out of the pipes if they don't have any bleeder valves? Would there be one valve for the entire system--that I just haven't found yet? (How many questions is that?)

I've always been told to bleed them at the beginning of every heating season.

Many thanks!

Ellie