My plumber did replace the old seal w/ a new one and all the rubber seals on the lid appear good.. it's only 4 yrs old so how can you test them?

Is the lid and seals slightly recessed into the floor? If so just pour a few cups of water on top of the lid. If the seal is good the water should just stand. No seal is 100% perfect so slowly draining off over several hours is fine. Are you getting any odors?

Great advice Bob! And if then lid isn't depressed put a little liquid detergent in some water and paint the rim. No bubbles and you're cool. Good luck, Tom

You really shouldn't need to worry about the seal on the lid because the pump should keep the water level in the tank down far enough so that it won't be under any pressure.You should just make sure the pump is always working properly.Usually the seals last longer than the pump.

Plumb382: lid has to be sealed to prevent sewer gas from escaping the pit.

I agree with Milo. Plumb382 fails to recognize that it's the sewer gas that the seals contain.
Back to Plumbing 101 for you Plumb382.
Cheers, Tom

I agree guys. Oh man, a fualty seal on a sewage ejector pit can stink a place up in short order. The water test is great advice, however, if you aren't getting any smells, I think you are good to go.