Layout Tank Inlet Hole Location
Then I can mark my center point for the inlet hole.
I marked this location this way so I could use standard 45 degree elbows to connect the pipe to the surround wall. I tried to position this hole as high up on the tank as possible. Not so high that it would not run into the thread lip where the lid screws on.
Drill Tank Inlet with Hole Saw
You don’t get a lot of second chances drilling holes in a big tank. So I took my time planning and thinking this through.
I used a large hole saw for the inlet and overflow pipes. On the slow setting, I drilled until the pilot bit pierced the tank, then clicked the drill in reverse to cut the big hole. This keeps the hole saw from grabbing. And this worked really well.
A rubber grommet fits in the hole and the pipe expands the rubber to make the seal against the plastic watertight. Then I push in a short piece of pipe. It’s tight and a bit of soapy water helps.
Make a Calming Inlet Pipe
So that water entering the tank does not stir up sediment, I’ll run a pipe to the bottom with two elbows to create a calming inlet.
This will keep the water from splashing as the tank fills. I glue up a 90 and 45 fitting and attach it to one end.
Then add a 90 to the other end.
Then set this in the tank and attach it with a stainless steel screw. In case I need to remove it at any time later.
Now, I can drill the hole for the overflow siphon.
Drill the Tank Overflow Hole
It’s just slightly lower than the inlet hole. And I needed it to rotated around this access hatch wall so it didn’t run into the inlet pipe.
Then a short piece of pipe is convinced strenuously that this is it’s new home.