There was some discussion in this thread about whether or not a main drain is necessary;

http://www.poolforum.com/pf2/showthr...-flow-reversal

My pool has a main drain; I've never seen an IG pool without one so I just took it for granted we needed one when we had our pool built.

After reading that thread, I greatly reduced the flow the main drain to see what would happen (our setup has a valve that can be closed to shut off the MD). It does seem the skimmers are performing better, but it hasn't been very long and it could just be we just haven't had as much debris in the pool this past week.

So far I've not noticed any negative affects, though I do notice that when I reduce flow from the MD the filter pressure drops. Does this mean I'm not getting as much flow out of the returns?

For reference my pool has 2 skimmers, 1 MD, and 3 returns (4 if you count were the pressure cleaner hooks up).

I look forward to reading other's input on this topic.