I want to put a sump tank into my system. I have no installed weir as well as no holes drilled. It’s not practical to drill without disrupting the whole tank. I’m considering the Tunze Overflow Weir but unsure on the water return pump. My question is, if you get a blockage on the weir what stops the return pump from continuously pumping to the point it over fills the main tank. Hopefully what I’m asking is clear and any help would be greatly appreciated.