Just got home and went to check if there is water in the basement from all the rain and the pipe that comes down from where the toilet drains into the floor upstairs is slowly leaking. It is a large (6 inch?) pipe and it is dripping all down it, mainly, it seems from where the joints are. Our house is 60 years old and this appears to be original. Do I need to call a plumber or can I fix this myself, and what kind of things should I expect to hear from a plumber if I do have to call one in? (costs, etc... ) Any info would be greatly appreciated!

First lets find out what type of pipe your working with ? Im guessing cast iron. Does it leak only after toilets flushed. Is there water in the toilet bowl ? Does the toilet run constantly ? Post back and let us know also a picture would be great if you can post one.

AC101 correct, you have to first determine where the leak is occurring.

Turn off water to toilet. If it is a drain leak, the dripping should stop shortly there after. It doesn't sound like a drain leak to me. If dripping does not stop the leak is in the water supply line. You must find a way to turn off water to that line. If the dripping continues after you turn off the cold water to that bath, turn off the hot. The leak will be in that wall but it could be a line to the sink or tub. Water will run along the bottom plate of a wall until it finds a way down.

What type of water piping do you have.

The pipe that is leaking is cast iron. The ceiling in the basement is open and you can see where it connects to the toilet, and there is no moisture around the wood there and the pipes from the tub and sink are not connected to the toilet pipe, they are all separate and visible on the ceiling in the basement, and are made of copper by the way. Could this be condensation? It has been extremely humid here (southern Ontario) and it was suggested to me that it could be condensation. I have never noticed this pipe "sweating" before however, but maybe I missed it. The toilet has been acting up and I wonder if there is a jam in it. Sometimes it runs and sometimes it won't fill. It is a newer kohler toilet so it should be working fine, but we do have three little ones flushing wads of paper down it daily so who knows. I guess my question is, if this is the large cast iron pipe leaking what must be done to fix it? Do we need to replace the pipe? Is there a way to stop the leaking without replacing it? How much would/should a plumber charge (roughly) for replacing it? Do these pipes usually need replacing after say 60 years usually? What would it be replaced with, pvc? Thanks!!

You get condensate on cold water pipes, not so much on drainage. With lead and oakum joints sometimes with age they will shrink and have to be recaulked, (see image). This does not mean that the joint will have to be poured again all the plumber would have to do is take his inside and outside caulking irons and recaulk the leaky joint. A 15 minute job. Good luck, Tom