I have been seeing water in the basement around the base of a very old vertical cast iron drain (soil) pipe. I have found several fine cracks in the pipe and so have tried to seal them by fiberglassing the pipe. But I got to thinking there must be standing water in the pipe and my effort to seal the cracks may be unnecessary. The toilets always flush properly but I'm thinking if I flush them (2) in rapid succession, I might get an overflow. I envision water standing in the pipe and then gradually going down so the leaking occurs when the water is standing and then subsides. In other words, the leaking is caused by a partial clog. There is a tee with a horizontal port just above the concrete basement floor. I am thinking I should remove the cleanout plug and check. What do you think I will find and will it be possible to remove the partial clog if one exists? I will drill a small pilot hole near the cleanout to check for standing water before removing the cleanout plug. Please, may I have your thoughts on this? Thanks very much for your advice!

 

No, do NOT drill a pilot hole. Then you've got a hole in your drain pipe. That's what the cleanout fitting is for and has a removable cap/plug that you unscrew.

You don't need to fill the pipe for it to leak. Just like how a window or your roof can leak without your house being totally under water. Water can seep out through cracks or leaky joints just by water flowing past.

It is possible you have a partial clog. Your test idea could tell you but you may need more water. Run the sinks and tubs for a minute or two then flush the toilets. Or, you can just snake out the drain line without the test since it won't hurt.

 

The pilot hole would be to check for standing water. A 1/4 inch hole would produce a forceful stream that could easily be caught in a pail as opposed to a flood with the cleanout removed. I'd then remove the cleanout plug. I'd then tap the pilot hole and plug with a brass or stainless machine screw with a rubber washer. I sincerely appreciate your comments! Good to know the pipe could leak without standing water. Did not remove the plug but did fiberglass the pipe using epoxy resin (to avoid the smell) and mat. Seems to have worked. (The pipe is original- house built circa 1920!) Thanks again.

 

My thoughts are that you have an older home probably built before 1950 and that cast iron stack has done it's job well over the years, but is nearing the end of it's useful life. How much water are you seeing on the floor? Is there any tracking down the vertical stack? Has the cast iron stack been painted? I believe I'd use a wire brush in a corded drill to clean the areas where the leaks appear to be and patch them using a thin layer of epoxy putty. I've heard leaks of this type referred to as boils and have found they are quite common on 70+ year old cast iron stacks.

 

I think you need to do some budgeting for plumbing repair/replacement. Resin and glass cloth are great Band-Aids but that's all they are. A temporary Band-Aid to something old and need of replacement.