At the turn of the century, the first indoor plumbing involved the use of lead pipes. These were replaced later with cast iron and by 1940 galvanized plumbing became the standard. Galvanized plumbing is made of steel with a galvanized interior, which makes the pipe more resistant to corrosion. It has now been replaced by the use of copper and plastic pipe.
Galvanized plumbing has a life expectancy of about twenty years depending on use and maintenance. After about 30 years, galvanized pipe with an interior diameter of half an inch can be reduced to a very small opening because of corrosion and buildup of lime, scale and rust.
Rust is easy to recognize in water quality. It turns the water a shade of red, orange or yellow. If leakage, rust or low water pressure is evident, the galvanized pipes are corroding internally and should be replaced either with copper or plastic pipe. The most effective way to establish the condition of the inside of galvanized plumbing is to remove a sample of pipe. By cutting out a small stretch of pipe it is easy to see how the interior walls are holding up and how much buildup there is. This is usually done on a horizontal stretch of pipe where water has an opportunity to sit stagnant. Vertical pipes are generally in better interior condition because gravity tends to keep them free of still water and debris.
Dark stains on the outside of the pipe do not necessarily indicate internal corrosion. Condensation around the pipe can cause flaking or staining, but is less likely to corrode the pipe from the outside in. Homes built before 1970 with galvanized pipes can expect to be in need of replumbing. Galvanized piping is still available but is seldom recommended for use.
Another tell-tale sign of wear is the presence of compression patches. Often when the pipe begins to rust out the leak is patched rather than replacing the pipe. A compression fitting is two pieces of metal with rubber seals and screws. They are tightened around the leaking pipe. It is easier to fix a leak in galvanized plumbing in this manner than to try to cut out the leak and replace it because it is almost impossible to create a threaded joint on a rusting pipe.
When galvanized pipes are connected to each other the joints are screwed consisting of threaded ends and couplings. Galvanized plumbing can be joined to plastic or copper pipes. When copper is used, a bi-metallic fitting is necessary. Brass is the most frequently used fitting because it is neutral to both copper and steel. If the metals are incompatible, a chemical reaction occurs which is caused by the positive and negative charges of electricity in the metals. Copper will react with steel in the presence of water and will corrode the steel. The brass or bimetallic fitting acts as a common ground between the two metals and can easily be soldered. Solders are typically antinomy tin or silver based. The use of lead solder has been illegal in Canada since 1988.
One of the problems with connecting plastic or copper plumbing to galvanized plumbing is the size of the pipe. Copper pipe has a thinner wall than galvanized. To ensure a common interior diameter, the outside of galvanized pipe would be about twice the diameter of copper. To make the internal diameter equal, a grooving machine is used. The pipe is slightly bent in order to create a groove on both ends. A rubber seal is used between the two pipes and then a coupling is fitted over the joint with solder. Galvanized pipe should not be welded because it gives off harmful fumes.
Galvanized plumbing is available in diameters of 3/8”- 4” and in lengths of 21 feet. Copper is available in diameters from 1/8”- 6” and comes in 12’ lengths. Plastic plumbing is available in almost any diameter and length, but the most common length is 12’. Copper pipes are soldered, steel pipes are threaded, cast iron uses oakum, and lead and plastic pipes require a chemical solvent or metal connection.
Neither copper nor plastic pipe corrode internally. Copper pipe has a life expectancy of 50-75 years. The lifespan of plastic pipes remains to be seen. Plastic pipes can leak at the joints because of problems with fittings and adhesives. As technology advances these problems are becoming fewer, but copper remains the most dependable and cost efficient in the long run. Both copper and plastic pipes are noisier than galvanized pipes.
The type of water that runs through the pipes has an effect on the life expectancy. Hard water has more impurities such as magnesium and calcium ions. These mineral deposits can build up in water pipes and add to corrosion and blockage. Water softeners can eliminate the problem.