BigEyedFish
In my opinion, having two separate sumps - not connected sharing common water - and running one overflow to each of these individual sumps will result in one or the other overflowing.
The overflows - if each is the same height in the tank - will do what they do - drain water.
The separate drains leading to each sump will take the water that drains.
The two return pumps do what they do - and pump water at some fairly fixed rate.
None of the equipment, pardon the phrase, "knows any better" and will just do what it does.
Problem is that there will eventually be a difference between the two sump levels. Could be a quick change you notice right away, or the level(s) could creep up or down over a period of time.
Up or down - neither one is too good a thing to happen.
Wet floor or burned up pump - or both.
Now if you were to use acyrlic tanks, or plastic containers, and connected the two sumps with bulkhead fittings and a length of pipe - it would work fine. The water will seek it's own (same) level in both sumps, being equal, no matter if one drain is dumping more into one sump than the other, no matter if one return pump is pumping more. But you'd have to make this connection line pretty good size relative to the changes that could occur.
A quarter inch tube may not be a good connection line size, something larger I'd imagine.
All sort of depends on the total rate of water moving up and back down, and the rate of change that would occur between the two sides.
If the rate of change between the two sumps was very small and did not occur quickly - a smaller balancing line would work.
If on the other hand, the rate of level change happend fast, you'd need a larger diameter pipe connecting both sumps - to make up for this faster rate of level(s) changing.
I think that's right.
