Cleaning Out Galvanized Water Pipes

By David S. Lawyer.
November 2007, Jan., Mar. 2008

When old galvanized pipes in your home build up rust and calcium deposits inside, water flows slow. One solution is to replace the pipes with copper (copper repiping). There are also strong chemicals that have been tried. A third way, an alternative to copper repiping, is to physically remove the rust and calcium (pipe deposits) by using an electric drill to rod out (drill out) the deposits. How to do this is as follows:

I did this for my home and the water now flows almost twice as fast (in gallons per minute). Here's how I did it. I first made a long drill bit about 22 ft. long by buying a 3/4 inch drill bit with a 1/2" shank and also buying a 21 ft. length of 3/8 inch galvanized steel pipe. Using a hammer and a block of wood so as not to damage the tip of the bit, I drove the drill bit shank into the pipe. The result is a 21+ ft. long drill bit suitable for drilling out scale from a long 3/4" straight galvanized water pipe.

Now I put this long bit into a 3/8 " electric drill. To do this, use a 3/8" to 1/8" reducer coupling and a short piece of 1/8" pipe a couple inches long. The 1/8" pipe (OD is about 3/8") fits nicely into the electric drill chuck, but it's best to file 3 flats on the 1/8" pipe so that it will not slip in the chuck during high torque.

So then with this 22 ft. bit, start drilling out the scale inside your old 3/4" galvanized pipes. It's a good idea to provide flowing water for both lubrication and removal of sediment when drilling. I used a faucet which was on the sprinkler system and thus didn't get shut off when I shut off water to the house. Using a hose and a special hose coupling I fed water thru the 3/4" pipe in a direction opposite to which I was drilling. This continuously washed out the deposit fragments busted up by the drill. But make sure you don't drill into the hose. For example, use a short length of clean pipe with one end connected to the end of the hose and the other end coupled to the end of the pipe you're cleaning. When the drilling gets too easy, you're at the end of the clogged pipe.

Don't let the drill stall. If it is about to stall, back off some (pull it back) so that it'll speed up and then go forward again. Of course a 1/2" electric drill would have been better but I didn't have one. Also, for pipes you've removed for drilling out, you obviously need to use a pipe wrench or vice to keep them from rotating when you drill them out.

Luckily, I have enough unions under the house so I can remove all of the 3/4" pipes that need removing so I can run the drill bit thru them. Elbows and tees can be cleaned out with a short drill bit and a screwdriver. Removing some exterior faucets allowed drilling from the outside without removing pipes. If you don't have enough unions to be able to remove pipe that needs to be removed, you could install unions. To do this, saw the pipes, rent a pipe threader, and install unions. A long straight run of 40 ft. could be drilled out (without removing) by drilling from each side.

For 1/2" branch lines I used a 1/2" snake made for sewer lines. The 1/2" pipes were not as badly clogged as the 3/4" pipes so this worked OK. None of the 1/2" pipes needed to be removed and were rodded out in place.

Then, after the job is done, turn on faucets to flush out the system. You may need to also open angle stop valves, since clogs of sediment may form behind them. In my case, I had to pound one with a hammer to free a clog. But even after flushing, the water may appear a little rusty. Flushing certain lines after a week or so helped. If it's only iron oxide (rust) and calcium, drinking this stuff shouldn't hurt you, but we drink purified water stored in glass jugs so it didn't affect us.

The rate of drill feed is at least a few feet per minute with a 3/8" electric drill so most of the working time is spent removing and reinstalling those pipe sections that need removing.

Buried pipe would be hard to do. But some buried pipes for watering landscape may not be too clogged up unless they've been heavily used. The long drill bit is somewhat flexible and might work on buried pipes if you dug a long, gently sloping, trench down to the buried pipe. But it may be better to use chemicals or to just dig up the buried pipe and replace it with a larger diameter pipe (say 1 1/4 inch galvanized) so that it it will take a very long time for it to clog up. Replacing it with copper is another possibility but then corrosion may form at the galvanized-to-copper union, even if it is insulated so as not to pass electric current. Such an insulating union might also impair the grounding of your house's electric power supply if it is grounded using water pipes.

You will find that the amount of scale build up is roughly proportional to the amount of water that has flowed thru the pipe over the past years. So the heaviest scale build up is in the line where the water from the meter enters the house.

They used extra strong 1/2" galvanized pipe to supply one of our bathrooms. This pipe is also extra small in inside diameter and thus clogs up easily. I removed some scale from it by pounding on it with a hammer while the water was flowing. My wife observed the rusty appearance of the water flowing out the faucet so she could tell me when further pounding was futile.