Well I did a trial run today to see if my 4HP compressor had what it took to blow out my MD, it did. Our plumbing consists of two main drains (both drains are connected to one 2” line), two skimmers (each on their own 2” line), two wall returns (both returns are connected to one 2” line) and two floor returns (both returns are connected to one 2” line).

In the process of blowing out the main drains and floor returns I wasn’t getting an even amount of bubbles from each drain or return line. When I was blowing out the drains most of the bubbles were coming out of only one drain. When I was blowing out the floor returns most if not all the air/bubbles were coming out of the return furthest (shallow end) from the equipment pad. Is it fair to say if I’m seeing large bubbles coming from at least one main drain and one floor return I should be ok as far as getting enough water out of the lines to winterize the pool?

If you have multiple main drains or floor returns on one line it is most likely that there is a T in the ground. Since the air you are blowing through will take the path of least resistance most if not all air will come out the closes return or main drain. Even with our blowers we will see more air coming out of one main drain than another when connected with a T. Regardless if you are getting a good amount out of at least one you are way below the frost zone and you are fine.