Hey fellas (ladies too),

I've got a small ranch house with 4inch cast iron waste pipe. When we bought the house, the inspector said the pipe would need replacing "soon". We've been in the house about a month now with no escaping sewage.

What are some tell-tale signs of cast-iron pipe being just about to rot through? Anything visible from the outside of the pipe?

Spots of rust and weeping will be your first sign. That or the pipe will clog because it has collapsed under the floor or outside.

As cast iron ages, it flakes off. If you knock on it, it should sound solid. Take a hammer and gently tap on it in one place. You will feel if the hammer bounces off like from a piece of healthy metal or from piece of pipe that is in advanced stages of deterioration.

We call Milo's test PLINKING. If you hear a nice plink with the hammer you are OK, if there is little bounce and more like a thund you have some work to do.

All right, some sections have a nice ringing "boink" sound when tapped, others have a hollow knocking sound. These sections have some visible rust and these funny little... well... nipple-looking things hanging off the bottom of the pipe.

I think you are a candidate for a replacement line. Most of us would recommend PVC but this may be more than a DIY job. Get 3 bids from plumbers and then decide if you can do it yourself.