Plumbing parts: How long before they need replacing?

Calling the plumber is one of a homeowner's most unpleasant experiences, but alas, occasionally it comes to pass. Plumbing wears out.

Nick Gromicko of the International Association of Certified Home Inspectors (NACHI), working from a report by the National Association of Home Builders, has listed the expected lifetimes of several plumbing components.

While many factors affect longevity, such as quality of materials, installation, and environmental conditions, there are some round numbers that you can use to judge a lifespan. Here is a look at some of the major components of your plumbing system.

Water-supply piping

You might find any of these three types of water-supply pipes in homes: galvanized steel, plastic and copper.

1. Galvanized: Starting with the worst first. Nowadays, galvanized pipes -- steel with a coating of zinc -- have no place in a home. They haven't been used for water systems since the 1960s. If you have a home with galvanized water pipes today, you may well have to replace them tomorrow; they could be on their last drips. Galvanized pipe can plug up two ways: it can rust from the inside, or hard water can cause scale deposits to build up. Or both. Telltale signs of problems include reduced water flow and rust spots caused by pinhole leaks. While galvanized pipe is not included on the NACHI and NAHB lists of estimated lifetimes, the rule of thumb is that it will last around 40 to 50 years if the water conditions are good. If they are bad, it could be half that, or less.
2. Copper: Unless you have pH-neutral water, your copper pipes can corrode; but the corrosion is much slower than with galvanized pipes. The NACHI chart gives them from 50 to 70 years; some plumbers will argue well over 70. But like galvanized, the conditions determine the lifetime -- some areas have very corrosive water. Also, electrical grounding can speed corrosion; the Catch-22 is that copper water systems must be grounded. While your pipes need to be grounded, you should not ground any appliances, such as refrigerators, to your pipes. And it has been argued that grounding direct current, such as a solar-cell system that charges batteries, could destroy the pipe in short order. Installation issues can also speed copper tubing corrosion: A rapid water flow, flux in the pipe from soldering or water turbulence can all remove the protective patina inside the pipe and open it up to corrosion.
3. Plastic: There are two types of plastic water-supply pipes, CPVC and PEX. CPVC pipe has glued fittings; PEX has either a crimped fitting, a screw-on compression fitting or a push-on (SharkBite) fitting. PEX can be bent, thus eliminating the need for many fittings at corners. The NACHI chart gives a rough life expectancy for CPVC of 50 to 75 years; PEX, 40 years. But NACHI does not explain the difference. Often, however, PEX fittings include brass or copper and could be subject to the same corrosion issues as copper piping. Like most plastics, both CPVC and PEX deteriorate in ultraviolet light and should not be used outdoors; also like other plastics, they tend to turn brittle over time.

Waste pipe

You will find three types of waste pipe in homes: cast iron, concrete/clay and plastic (ABS or PVC).

1. Cast Iron: The NACHI chart rates cast iron waste pipe at from 50 to 60 years, though it can last longer -- the NAHB says cast-iron systems can last up to 100 years, but there is a lot of anecdotal information from plumbers about cast iron being ruined in under 40 years. Cast iron will rust from the inside out. It is thick pipe and usually will take a long time to rust through, even in bad water conditions. Tapping on the outside of the pipe will reveal weak spots, if the pipe is severely corroded. You also can inspect the interior of the pipe with a camera -- an expensive process.
2. Concrete/clay: Both the NACHI and NAHB charts say concrete waste pipe will last 100 years; they don't mention clay, but it also is long-lived. But these pipes do have problems that you need to get to the root of - literally. Tree roots will grow into the joints and plug up the pipes - nothing like a good lunch for a hungry tree. Sometimes the concrete will break as the roots grow. Root invasion can happen rapidly if there is the slightest leakage around the joints of the concrete and the extreme lifetime becomes a mute point.
3. Plastic: PVC is the more common plastic waste pipe for connecting the house to the street. ABS, black plastic, is the more common inside the home. The NACHI chart gives them a 50- to 80-year lifespan. Both materials will become brittle with age.

Toilets

A toilet can last a long time -- both NACHI and NAHB give it 100 years, unless it suffers some external abuse, such as a sledgehammer. Of course, that is referring to the porcelain part; the internal workings -- the lever, flapper and valve -- may have to be replaced every few years. If the water supply is very hard, the holes under the rim of the toilet from which water flows into the bowl can plug after several years and need a tedious and time-consuming cleaning.

Faucets

Both organizations give faucets a lifespan of 15 to 20 years, but of course their lifespan is very dependant on the usage and quality of materials. Cheaper faucets may be plastic; the plating may be cheap or high quality. Often, a faucet will lose its plating and while the water control works well, it becomes unsightly.

The important thing to remember on any of the lifespans is that they are truly variable, depending on conditions and the original quality of the product. Just because one element has a life expectancy of 20 years doesn't mean it won't fail after half of that, or live twice as long.