Hi,

Last week we had a clogged main. The main pipe access is down at the sump pit in the basement and the plumber couldn't open the caps (very old pipe, never opened before). Eventually he just drilled a hole on the cap to get the snake in and cleaned. After that, we just kind of use a plastic bag to cover the hole. Do I really need to seal the hole with something? I don't smell any odor from the hole and somehow I think it is a good idea to leave it like that because if the next time it backs up again, the water would come out from the hole which is in the pit which can hold probably 20-30 gals of water instead of backing up from the toilet in the basement like last time which made a mess... Or am I wrong? Thanks

How big is the hole? You could possibly tap it with a 3/4 or 1" pipe tap and thread in a plug. Or, put in a pipe nipple and a cap.

Let me see if I understand your problem. By cap do you mean the cover on a clean out tee and instead of removing the cover he simply drilled through the brass cap? Is that correct? Please explain "caps".
One things for sure. You can't leave the hole open. But before I tell you how to repair and cover the hole I have to know exactly where he drilled it. Please post back with more details. Tom

The cap should be and can be completely removed. By putting a plastic bag over it your sewage will be all over that room if it backs up again. I would remove all of the old cap and replace it with a new one from the lumber yard about 4 or 5 bucks.

Hope the pics work...
There are two caps (openings) to the main down at the pit... I think it is a U? The guy spent an hour and couldn't open the cap, so he actually cut (sorry, not drill) a hole and then cleaned it and I am not sure if I should get it sealed or it is OK to just cover it with a plastic sheet or bag... people say there could be sewer gas or something?

http://i44.tinypic.com/2mh90z6.jpg
http://i43.tinypic.com/2qk6mv6.jpg

http://i43.tinypic.com/2qk6mv6.jpg

The cap should be replaced or the hole sealed. If there is a hub, you could buy Jim Cap and install it over the hub. In any case, the hole cannot stay the way it is now and has to be sealed. Milo

Looks like a threaded cleanout plug to me. I would remove the rest of the plug and use an expansion plug of the correct size in its place. An expansion plug of the correct size will seal the cleanout nicely, and also be much easier to remove in the future for snaking.