How to locate leak in low-pressure 4" cast iron drain pipe

[vintshave]

I have a 110 year old Philadelphia 3 story house. I've been noticing a persistent pool of water in the basement near my water heater. It never gets large and it never goes away. All of the upstairs waste water drains through that original 110 year old cast iron pipe - 2 tubs and 3 sinks. I felt along the pipe in the basement and could find damp spots, but couldn't identify the source. So I turned on the tub and went back downstairs. I saw trails of water flowing down the pipe. The bad news it that I saw the water flow coming up from as far as the basement ceiling, so it must be originating from above the floor. Directly above the floor is a 110 year old floor-to-ceiling plaster "box" around the pipe. I have to figure out where along the pipe the leak is and repair it. I assume that entails smashing plaster to get to the pipe.

How would I accomplish this with the least amount of destruction done to my house and what would you recommend as being the most economical way to repair it? I have a budget of a couple of hundred dollars, but I'm a very handy guy, own a sledgehammer and am willing to get my hands, arms and face wet and dirty.

John

 

[havasu]

We're going to need pictures in order to help you.

 

[vintshave]

Here are some photos of the areas concerned, with notes on them.

 

[vintshave]

Are those photos helpful? The show everything I can access

 

[havasu]

Yes, they are helpful... somewhat. The problem though is that everything is encased, so nobody can really help you except to say that water only travels downhill (normally) so you need to excavate to the point that everything is dry. I'm hoping that someone with experience will chime in soon to help you.

 

[phishfood]

I would remove the plaster box, and whatever of the ceiling that you have to, and replace every bit of the cast iron pipe that you can get to. It is 110 year old metal pipe that rusts, and it has started to fail, it is way overdue to be replaced.

 

[vintshave]

Yes, they are helpful... somewhat. The problem though is that everything is encased, so nobody can really help you except to say that water only travels downhill (normally) so you need to excavate to the point that everything is dry. I'm hoping that someone with experience will chime in soon to help you.

My guess is that since the ceiling isn't wet, that the leak is somewhere on the vertical section of the pipe. Regardless, not terribly good news. Cutting into walls is never fun (unless you're getting paid for it and you don't have to clean up the mess). Cutting into plaster is the square root of the normal fun of cutting into a wall

 

[johnjh2o]

My guess would be that if it's all the original plumbing the tub trap is lead and that is were the leak maybe coming from.

 

[vintshave]

What's the best way to get to the tub trap without causing significant destruction? Also, how would I repair it?

 

[johnjh2o]

Open the ceiling under the tub. Replacing a lead trap is not a DIY job. Call a plumber.

 

[vintshave]

In this project, where are the pipes in the ceiling likely to be? I know exactly where the 4" waste pipe is, but what's the best way to approximate the location of the tub, toilet and sink piping?