Wrong overflow level?

[Water Dog]

That would be a nice temporary failsafe to use a float switch to kill your return pump if the water level eats too high while you work on redoing your plumbing.

 

[toads74]

Don’t rely on emergency shutoff switches, check valves etc. eventually they will fail, get blocked etc.

Properly setting the maximum amount of water in the system will ensure such overflow disasters can’t occur, short of something actually breaking.

run The system for a few minutes with the overflow drains at the desired height relative to the weir (Where it’s quietest). Then take out small amounts of water until the return pump starts sucking in a little bit of air. Shut off the return pump, wait for the tank to stop draining. This is your minimum water level. Mark it on the sump.

next, we need to set the upper limit. This is the lesser of what the tank can hold under a worst case blockage of the drains, and how much the sump will hold when the return pump is off.

being very careful of course, block all the drains from the tank to the sump. Let the return pump empty the return chamber of the sump until it is sucking air. Then, keeping the return chamber empty and pump running, add some water, making sure not to overfill the overflow box. Check the sump level by shutting off the return pump and unblocking the drains, let it drain back until it stops. It may also drain via the return line in addition to the drain, this is fine. Repeat this process adding a little water at a time until either the sump or the tank is as high as you feel comfortable with. When satisfied, shut off the return pump, wait for the tank to stop draining. This will be your maximum Water level. Never fill above this.