On my first install, I am learning the strange relationship with air and water. I have six growbeds on a 4x8' table. I thought I could drain the three beds on one side of the table in a common pipe and the three on the other side into one and Tee them before draining into the sump. When I did this, as one growbed siphoned & drained, it created a ripple effect & caused all the beds to drain even tho they were not filled to the top of the standpipe. I presume my return pipe is not large enough? Do I need to drain each bed seperately into the sump. I will be adding another table soon with six more beds. That would mean 12 different pipes returning to the sump?
Any help is much appreciated!
It is creating a universal siphon in the one pipe because it is probably not large enough. You could simply put a T in the single pipe and come up to a level above the grow beds to suck air reduce the siphon effect on the other beds. Or just put an oversized pipe in as your main drain line so there is always air.
Larger pipe for combined drains is always a good thing. Also, vents as Jonathan notes (the T with a pipe going up above the bed height) can reduce the siphon effect of one bed siphon kicking in and causing the other beds to siphon at the same time. I've used a combination to keep combined drains from being a problem.
you could also run your drain pipe from your bed in to the line going to your sump with a small air gap between to prevent the siphon you could build an air gap like this cheap