Oh boy, Im supposed to remember this kind of thing from when I served my apprenticeship. I believe, that you are limited to 32 feet with a a pump that relies on atmospheric pressure to do the lifting. It takes 1/2 lb of pressure to lift water one foot so 14.7 psi X 2 = 29.4 feet. Thats pretty close. There may be some effects of the pump creating a partial vacuum that I dont remember to make up the extra 2 or so feet. <br> If you only have to pump a maximum of 20 feet, I see no problem.