Kevin:
This question comes up a lot. I feel that there are several factors that play into whether or not a compressor will be efficient enough to accomplish the task of blowing out all the lines properly. It is not pressure that is needed, but more volume.
...The distance and size of your plumbing to each return, skimmer and main drain are items to consider.
... Lowering water below the skimmer and returns make a huge difference in blowing out these areas. If water is lowered, one can literally vacuum most of the water out of the lines first and then blow the remaining water out.
... Having the appropriate shut off valves in where one can isolate each section is important as well.
... Where you are blowing the air from and if the elevation of the area is higher or lower than return jets and skimmers.
Below, please find a thread (Post # 10) which describes the experience a member has had with a pancake compressor.
Closing: blosing out lines, water level and then some
From speaking with the manufacturer, the Cyclone produces about 5 psi, and with the resistance of the water, the return jets are at about 90 cfm and main drain about 30 cfm. Under no pressure, the unit produces 130 cfm. The bubbling effect of the main is real powerful.
I would assume that an air compressor that can produce 10 cfm may be sufficient to move the water below the frost line. There is also a difference of the hose involved. The 1.5" hose creates a lot more air than your standard air compressor hose.
Please take a look at post # 15 and this describes the amount of CFM needed and for what. If one can isolate each area when closing, the task is accomplished a lot easier. This also assumes 2" plumbing, which creates less resistance. Some pools have 1"-1.5", which may require more cfm. The information is from another member on the forum, but I can not recall who wrote the post as it was copied.
Problem blowing out pool lines
