Many people argue that they have "blown out my RV water lines for umpteen years, and never had a problem" Using an air compressor to blow out your RV water lines vrs winterizing with RV antifreeze. Mind if I ask where you found your are the cold and hot water line drain lines with shut off valves? It’s also important that you blow out as much water as you can from your sprinkler lines, especially if your system uses pipes with smaller diameters. I much prefer your method of … Mike goes on to say that if your system flows 20 GPM of water at 30 PSI, then you divide the 20 GPM by 7.5 to get the CFM necessary to adequately blow out your lines. Next, open the manual drain valve at the end of that zone (if equipped). Screw the Blow-Out Hose into your RV's city water inlet, then connect your air compressor quick-connect hose. Then, connect the air line to the blow-out port as shown. Unlike other blow-out systems, this system leaves your hands free to open faucets and flush out water lines without assistance. Maybe also how long it takes to blow out the main drain. Or put antifreeze in the lines would work too. I have a 2013 Big Country and for the life of me can't find the external water lines with valves that will allow me to drain and blow out the lines. ShopVacs are not made for pressure, but for volume. If they sink back down, you don't have enough volume available to hold them up. It is volume that is more important than PSI. This is an accessory to your normal winterizing procedure. Personally I have had bad luck blowing pipes out. For if you don’t, the pipes or the hot water tank could expand and burst from the ice. Darcy it all depends on the plumbing in your equipment and distance run to the pool and what you are trying to evacuate water out of ie skimmers, return jets, waterfalls, water supply lines to slides etc. The volume flow rate really does not matter. Just to check that theory, You can blow the water out, Let the compressor come back up to pressure and try it again. Tell us how it works out and what settings you have it on. Then turn off the water supply and set the system timer to open just one zone. Water can easily flow back down the pipe to the low spot after you stop blowing air through. Set the compressor air pressure regulator to a maximum of 80 psi for rigid PVC pipe systems, or 50 psi for flexible black polyethylene pipe. You could also use a wet vacuum cleaner and suck the water out. Blowing out sprinkler lines with a compressor is one of the most effective means of winterizing a sprinkler system. Blowing out lines first just means there is less chance to have the antifreeze diluted with water. Every winter before it freezes, it’s important to winterize any trailer that has running water capabilities.