2 Tank Sump

I swear I have seen people with a two tank sump systems.  How is this accomplished to remove the possibility of over-flowing?  How do you control the flow in both tanks?

I have a two tanks with a single sump.  One tank is a 75g frag tank and the other is a 150g display.  I did have both running off of a single return pump but due to the distance and head I had to run, I now run 2 return pumps but am planing on returning to a single return pump once I buy the correct fittings again.  On my system with a single return pump, I used valves to control the amount of flow going to each tank.  However, as I said I had a big distance to go, so I only slowed down the flow to the frag tank because it was closer to the pump and I needed the extra pressure to get the water up 25ft.
As far as overflowing, you just need to make sure your sump is large enough to hold all the excess water from the multiple tanks in case of a power outage or equipment failure.  Even on a single tank and sump setup, you want to make sure you have enough room to accommodate the water when something bad happens.
If you're ever in the Kaysville area you can come take a look at my system...

Sitaga, its really simple to have a two sump system. I have plumbed many before and plumbed one just the other week. I usually will put my equipment in one to keep stuff clean in that sump then have one for the client if they want a fuge. My last two sump system was just under 200 gallons. with a 110 gallon fuge to help the tank stay clean. I have switched over to a Sulfer reactor to control No3 in fish heavy tanks as well but this still works good. I will get you some pictures sometime in the next week. But you can control them easy it all depends on what you would like to plumb. This last one I did. I had one overflow going into the fuge and the other overflow going into filter socks. If you drill both tanks and have at the same level as each other and have the same plumbing to the pump you will be fine and will find out the water is suction out of both sumps evenly. Then when power is off they will drain into each other giving you a nice big area to empty into.

Do you want both sumps plumbed or two tanks plumbed?

So you want to drill your sumps together. The tanks abouve will drain into them without a problem. You will need to put ball valves onto the pump to control how much flow goes into the tank so you don't have a flood. If you drill your sumps together at the same height and have a level pipe, and floor the water in the sumps will be the same. The pump will only suck out the same amount that is going in do to pressure. I have a two sump system that the majority of the water goes in one sump 80% and then the other sump is a fuge and only 20% of the water goes in there but both are the same level. You have to have your plumbing in line and make sure that you are equal in both pipes till they run to your pump. It sounds like its hard but it isn't. If you didn't live so far away I would come up and help you.