[stewartlong]

I have an old air compressor with a tank that does not have a drain plug underneith.

It was a replacement tank from 20 years ago.

How can I drill, tap and install one so it doesn't leak?

Or is it time to just junk it out all together?

 

[Fix'n it]

you would have to have a bung welded on.

 

[joecaption]

Time to junk it.
It's not legal to drill or weld on a pressure vessel unless you go have it static tested some place.

 

[woodworkbykirk]

junk it or take it to a local authrorized air tool repair shop

 

[md2lgyk]

Compressors aren't very expensive any more, and there are lots to choose from. I wouldn't put a dime into one that's more than 20 years old.