Why my pool pump gets air whenever I open the main drain line?

Question

Why my pool pump gets air whenever I open the main drain line?

Answer 1

I think it's because of a vacuum inside the pump pool. When you open the drain line, it creates a shift of water between both these open vacuum spaces and causes a shift in water and air. So I guess the air shifts to your pool pump.

I've had the same thing happen to my backyard pool in my Atlanta, Georgia house.

Hope this helps.

Answer 2

could be either a leak in the main drain line is letting in air,OR the main drain is clogged and the pump runs dry from lack of water OR a combination of the two.

A way to test is have BOTH the skimmer and main drain open and see what happens...air in pump is leak,no change is probably clogged line...if the main drain IS clogged,the additional force of the vacuum may be revealing an air leak from somewhere else

heres a few more tips: http://www.swimming-pool-information.com...