You can seal that existing sump pit by removing any existing lid and getting a square of plexiglass bigger than the pit and drill a hole for the pipe and cord and then screwing the plexiglass to the concrete floor with a bead if silicone under it to make the seal.
We don't cut it round. We get a square in the size we need from the hardware store and then use a holesaw for the hole for the pipe and cord. We pre drill some holes for screws and put it down and then mark up the holes on the floor. Then we remove it and drill the concrete. We put a thick bead of clear silicone around and put the plexiglass back down and screw it in. Admittedly you likely will not get it off again to replace the pump because of the silicone but so far we have not had to remove one. We have only done it that way a few times when radon was an afterthought and we ran the pipe up and out the sidewall in the basement. We don't have radon codes here in the plumbing book but they are working on it since its only in the construction book and very vague.And you can see through!But I bet it would crack when trying to cut it round.
No. I was wondering the same but thus is how I was told to do it and the fan is rated for outdoors use so I take it that it might have an internal design directing the water safely past the motor. The man who signs my paychecks told me to do it that way so that is how it went in. If I felt it was safety issue or something really totally hacked then I would object. Just because I would personally prefer a different approach does not mean I have good grounds to stand on for objecting. The luxury of having the final say is reserved for the boss not the employee. The end of this year or beginning of next I will have that luxury myself.
But I bet it would crack when trying to cut it round.
