3/4" x 3/4" x 1" Tee?

I have a leak in a threaded PVC plug with a 1/2" thread. The plug is in a 2" diameter 90 degree PVC elbow in a pool skimmer line (See attached pictures).

The existing thread in the elbow has play and the plug can't be tighten.

One way to fix it would be to enlarge the 1/2" threaded hole to 3/4" and use a 3/4" plug. Can anyone tell me how to drill a larger threaded hole? I don't know what tool I would need to do that.

Are there any other ways of fixing this leak?

Thanks
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I would like to fill a hole in my basement floor with concrete in order to prevent ground water from running up through the hole when we get heavy rains. My house sits at the bottom of a hill so when it rains heavily this hole fills with water even though my sump pump is keeping up on the other side of the basement. Here is the hole in question: [url]http://i.imgur.com/nRPQIRa.jpg[/url] Here is a close up of the hole: [url]http://i.imgur.com/UWtsV7M.jpg[/url] This is 180 degrees from the hole: [url]http://i.imgur.com/Fu4tL6p.jpg[/url] The orange cap on the PVC pipe slips on and off easily. I can't tell where the pipe goes but I'm guessing it connects to that larger pipe there against the wall. In any case, we don't plan on doing anything with the plumbing fixtures in the basement any time soon so our greater concern is preventing water leakage. We have been in the house for three years and the only time water leaks out of the hole is during extremely heavy rains so it is not common but we want to put a little entertainment area in the basement and don't want our furniture getting wet. So my question is: Before I fill up the hole I would like to bring the pipe above the floor. Can I just use a 90 degree joint or should I dig down a little farther and use a P-trap? Are there any other things I should take into consideration prior to filling with concrete?