oops - morning floods on the floor

on the bottom

 

Ok, so then you'll just need a small hole in your return hose just below the surface of your DT. Usually in the lock-line.

 

This is not a reliable way to create a siphon break.The small hole can easily be clogged or blocked by algae or a snail,I've had it happen several times.The safest way to have a siphon break is to position your return nozzle close enough to the surface so that it runs out of water before your sump can overflow.To guard against a DT overflow simply set your overflow so that yout tank can hold the extra water volume should the overflow stop working and your return pump section of your sump is pumped into it.The only other concern would be your ATO,if that were to continue to add water to the now low return section that water will be pumped up to the tank as well.There are several solutions to that problem.Some people use a controller and high water sensor that shuts down the return pump.I use a Tunze nano ATO,it has it's own little control module that shuts it down after 45 seconds should it continue to run that long.That equates to about 1/2 gallon added to the system.It also works should the ATO reservoir become empty so that the little pump does not continue to run and possibly burn out.My sump has been functional for about six months now and these three things have worked to keep all water where it belongs.You're going to love having a sump once you get it set up and see how everything works.