if you remove the bulkhead then you are left with a chamber with a hole at the bottom. Place a bucket under the hole, place a pump in the bucket with a hose going to your sink. Get your garden hose and run water into the chamber, then continuously pump the water from the bucket to the sink. Run water continuously until clean.
You can use a long handle brush to clean the bottom as water is running through
the black sch 40 bulkheads are pretty flimsy, but so much cheaper. Just had to replace one meself. Anything that would be disasterous if it broke, ie pump/pressure/return side, go for the sch 80 and avoid the nightmare.
This sounds like a plan. Now, if I just had your long arms (I was going to crack a primate joke here but let it go), it would be really easy.
I'm also wondering, since I'm replacing one bulkhead, if I should just bite the bullet and replace the return bulkhead as well.
I'm also now considering whether I should hard plumb my return pump. I like the idea of getting the heat out of the water column but it does add to the footprint in the stand. Then again, that's a fun decision to work on (as opposed to the stupid leak).
Most likely your leemar tank is drilled for sch 40 bulk heads. You will not be able to fit sch 80 bulk heads in you overflow. Sch 80 bulk heads are used for closed loop systems or big nasty tanks like Elliott's. In an overflow box there is only pressure of 4 or 5 gallons so there is no need for sch 80.
IME 99.9 percent of bulkhead leaks come from one grain of sand under the gasket. I would do as Elliot suggested and clean that overflow first then clean the bulkhead gasket and try again. If it doesnt work you have to get another bulkhead. Just FYI ocean floor carries both 40 and 80 bulkheads. But i dont see a reason for 80's ever even in mega systems.
Dang, I'm going to need more flow. Thanks for the input.