DIY Sump and filter?

The trick is to use an overflow of some sort to return water from the tank to the sump. This can either be a simple overflow through a hole drilled in the tank, or a more elaborate syphon system. Either way the level in the tank is controlled by the overflow, more water pumped into the tank, more runs out the overflow into the sump. Once the level in the tank drops a little then the overflow stops.

Within reason the pump size doesn't matter, and the sump just needs to contain enough free space for the extra water in the pipes to run back into the sump.

Ian

regarding the pump size, you have to match the overflow pipe with the return pump. the bigger your overflow tube is the higher the flow. also, you should maximize the head or the difference in height between the overflow inlet and the outlet as this has a direct effect on the flow rate. you could also add more overflow pipes if you want to increase the flowrate. the size of the pump depends on your tank and the turnover rate you desire. you just have to design the overflow to handle the volume. it also depends on the size of your sump, when the pump is running, the water level will drop because the tank level will naturally rise to feed the overflow. you can not just top it off while its running because once the pump stops for any reason, the sump will overflow unless you have an overflow in the sump as well.

when i built my sump. i installed an overflow on it but i also built in a device to top off the sump automatically. similar to what tou find in a water storage tank or water closet.

what size tank and what size sump? Is it a drilled tank with overflows? Basically the return has to be sized in accordance to your drain if you pump water up faster than it can drain is where the problem of overflowing the main tank will come into play. So if you can drain faster than you can pump water up there will be no issue because then the drain will only go as fast as water is pumped up.