I know this is really old, but I can't not say this. Supply lines are not and will not be made of clay. As someone posted earlier those are sewer lines. Tree roots make their way into clay sewer lines all the time. Yes, they can be lined to prevent storm water and roots from making their way into your sewer line, but the point of this is to keep the non-pressurized waste water flowing OUT of your home and not backing up into your floor drains or elsewhere. If a tree root somehow made it's way into a supply line (the water coming IN to your house), you would have quite a mess in your yard as the 50+ psi in the municipal water system would shoot water all the way up to the surface of the ground and out. It's very unlikely that you could be unaware that the main water supply (service) line into your house has broken. I've never heard of a tree root breaking through a metal supply line. They do break, but typically not because of roots. They fail because of corrosion, bad fittings at the city shut off valve (b-box), freezing or the earth shifting underground and shearing the pipe. Sewer lines get clogged with tree roots all the time and our country is full of clay lines that have cracked/separated/collapsed/failed over time. Nowadays various forms of plastic are a more typical material to use for installing sewer lines because they are not expected to degrade the way that we now know that clay will. I too am interested in whether it's possible to clean out clogged galvanized lines without replacing them, but it doesn't seem like a reliable method of doing this exists. I'd like to know what the original poster ended up doing.

So after 3 more hours of digging last night, I found the root of the problem...yes, roots!!! Also, I found that the beginning of the pipe that comes out from the foundation is 4 inch cast iron, it is then connected to a thicker concrete-like pipe. The first piece makes a 90 degree turn and then each piece is about 3 feet long, the outside diameter is about 5.5 inches and each connection has some roots going into it. My plan is to install the clean-out next to the cast iron, and then replace the next 3-4 sections of concrete with 4 inch PVC based on your advice using the no-hub clamps. My problem now is, how do I connect between PVC and the concrete pipe? I'm not sure how to attach pictures here, but I uploaded 3 pictures on my website, so you will get a good look at the situation. http://www.geocities.com/fcandreasson/ Thanks again! Here is a link that might be useful: Sewer Pipes

Try Baking soda and vinegar. dump in the baking soda and follow it up with the vinegar. should clean it right out. Also read the article linked to at Mother Earth News. Cleaning drains without chemicals. They also ran an article recently on cleaning products without harsh chemicals. Here is a link that might be useful: clean drains without chemicals article

You could enclose them in a decorative column (floor to ceiling) painted to match other trim in the basement.