Can you use two sumps running separately on a dual overflow system?

I don't know how you can say this. This statement is completely inaccurate. If you have two separate sumps with two separate returns from the same tank then inevitably one overflow will allow more water to drain than the other - OR - one pump will pump harder than the other - OR - both and you'll have one sump eventually run dry.

Additionally, if one pump blows then you can overflow a sump. Not a good idea unless the two sumps are plumbed together to equalize the levels.

 

He has two outflow. 2 Drains. Not one drain, not one sump. They are not running in parallel, but independently. There is no difference between running a single sump in this case, vs. the 2 he was asking about.

It is irrelevant that one sump may have a higher flow rate than the other, they have no link to each other besides being a portion of the same DT.

Either way if they run independent the returns will equalize the flow out of the tank, resulting in balance once again. True that if one pump was to fail then he could have an overflowed sump, but this is handled the same as any other sump set up, with back pressure floats and stand pipes.

If I understand what you are saying correctly, then you are assuming he is jumping one sump off of the other by means of a secondary pump resulting in this type of chain DT>sump1>return1>sump2>returned to DT. This would be impossible, but if each drain deals is separate from their other, this is not the senario being presented.

 

NO, it won't, there is no way to guarantee that both sumps get the same amount of overflow as the return pump is pumping.... And there is no way to set the ATO... You will end up either flooding or running a pump dry if you try this. You have to have the two connected in case of the emergency that is basically guaranteed to happen.

 

I think there is miscommunication on what is being asked. I don't believe he is referring to a tank with a single overflow box and dual outlets from said box, but rather a tank with dual rear overflow boxes each with a single line out. In which case they need not be balanced with one another, only with themselves independently.

Such as this tank



Each overflow will work completely independently.

 

the sumps would need to be connected in some way I think, And i personally would trust using two pumps for returns, I'd do one sump, with one return pump.

 

The two sumps do need to be connected. If each can handle the overflow independently, one or the other would otherwise run dry (if they cant independantly handle the overflow, there would be a spill). You could handle it with ball valves, but it would be very hard to adjust.

It is easy to link the sumps though. It's as simple as filling a hose with water then, with both ends capped off, putting one end under water in each sump. The result is a u-tube siphon that will balance the levels. Some PVC pipe, some elbows, and a way to suck the air out of the piping accomplishes the same thing.

 

I think the confusion comes from this, I fell for the same error initially. They are actually dependent though since they both drain from the same body of water. Picture them at equilibrium with no water draining but excess water in the sumps. One sump has a 100gph pump, the other, 10gph. When you turn them on and run for an hour, 110 goes in then drains 55g into each sump. In the next hour, the bigger pump drains 55g in a bit over 30 minutes then runs dry (in reality, this is more on and off sputtering and air bubbles, but it's easier to think about this way) while the other ends the hour with 45g still to pump. Ultimately the return rate settles at about the return rate of the smaller pump.

 

It is completely relevant and there is definitely a link - it's called the display tank and the water level in the tank.

I can't tell you how wrong you are here. Look at an extreme example:

Let's say in one sump let's say you have a 450 gph pump because it is working great, but in the other it is clogged and running at 150 gph

Now let's say you have two equal drains because they are new, have no obstructions and are at the same level. Because the pumps are putting 600 gph into the tank, they drain at 300 gph each.

Do you get the picture now? One drain is putting 300 gph into a sump that has a 450 gph coming out of it - it will eventually run dry.

The other drain is putting 300 gph into a sump that has only 150 gph coming out of it. It will potentially overflow.

 

Even if you could possibly some how run two sumps and return pumps, why would you want to? It would cost more money and just complicate things.

 

I can't express how much I disagree with the notion this will work. I am positive it's going to end in disaster. There is no confusion. There is no way to make them independent. Gravity just doesn't work this way.