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Plumbing Mike Last

Step into a shower and feel the relaxing pulse of hot water. Toss a load of dirty clothes in the washer, add some detergent, and press a button to have everything clean in under an hour. Yes, it’s easy to take household plumbing for granted.

But the wonder of water on demand becomes more apparent when something goes wrong, or when a remodeling project calls for new supply, drain and vent lines to be installed. Many plumbing problems can be traced to faulty installation details. Fortunately, plumbing materials, procedures, and design details are covered extensively in the Uniform Plumbing Code (UPC), which is the reference guide used by licensed plumbers and most building departments.

Whether you are tackling a DIY plumbing project or working with a professional plumber, the details here will help you make basic decisions about your existing plumbing system or planned modifications.

Main Systems & How They Work

Supply lines deliver water for use throughout the house

There are two primary ways for homes to get water: from a well or from a local water utility. If a utility supplies the water, there will be a water meter and main shutoff valve on the main supply line that enters the house.

If water comes from a well on the property, there will be a large storage tank that is filled by a well pump. You’ll find a shutoff valve on the pipe that feeds the tank (from the well) and on the pipe that feeds the water heater and all the cold water lines that extend to different parts of the house. It’s important to know where these shutoff valves are (and to keep them accessible) in case there’s a problem with your plumbing system that requires turning off the water.

In older houses (those built prior to 1970), supply lines were typically fabricated from copper tubing and copper or brass fittings. Newer houses are more likely to have plastic supply lines (see PLUMBING PIPE, below). Older houses that have been remodeled often have a combination of copper and plastic supply lines.

Water treatment systems remove pollutants

If you get water from a municipal water supply, it will be treated to remove pollutants that are health hazards. Well water is untreated. Regardless of which water source you have, it’s important to test your water to make sure it’s safe. (A search for “water testing” in your area will yield a number of companies that can test your water.) Well water can be contaminated with bacteria, chemicals, minerals, or radon.

Municipal water can also carry contaminants. A water test will identify specific contaminants, including minerals like iron. While not toxic, minerals can shorten the life of a water heater and cause difficulties with washing. The results of a water test will tell you what types of water treatment are necessary. With well water, it’s not uncommon to have two or more treatments –to remove bacteria, radon, and minerals, for example.

Waste lines drain to a septic system or municipal sewer

The waste lines that drain dirty water are easy to distinguish because they’re much larger than water supply lines. These days, most waste and vent lines are made of plastic (see PLUMBING PIPE, below). In older houses, waste lines may be copper or cast iron. In rural areas, waste water is piped to a septic tank that feeds a septic field composed of perforated pipe bedded in gravel. Liquid effluent is distributed throughout the septic field, making gains in purity as it percolates through gravel and into the soil. Solids settle in the septic tank, and must be pumped out at least once a year –more frequently, under conditions of heavy use.

In urban areas and many suburbs, waste water is piped to a municipal sewer system. Fees for municipal water and sewer systems are based on water usage, which is recorded by the water meter installed on your home’s main supply line.

Plumbing vents ensure good drainage

All plumbing drain lines require vents to ensure good drainage. Without the makeup air that ventilation provides, vacuum action can impede the movement of waste water through drain lines. Every plumbing fixture (sink, toilet, shower, washing machine, etc.) must be vented, but some fixtures can share a vent line. Venting guidelines are provided in the UPC. Conventional vents are assembled from plastic pipe, and run through stud bays and attic space to extend through the roof. When it’s not possible to vent a fixture conventionally (like venting a sink located in a kitchen island), most building codes will allow an air admittance valve (AAV) vent to be installed instead.

Plumbing Pipes

Plastic pipe

There are three main types of plastic pipe used in residential plumbing. Each type has particular characteristics that determine best uses, but in terms of overall performance, plastic pipe has distinct advantages over metal pipe. It will not corrode or interact with minerals in the water supply, like copper and cast iron pipe can. Unlike metal pipe, it does provide some insulation value. And it’s easier to work with because fittings are joined to pipe with solvent or compression joints rather than solder.

  • PVC (polyvinyl chloride) pipe is primarily used for drainage and for cold water supply lines.
  • CPVC (chlorinated polyvinyl chloride) pipe is more expensive than PVC, and is most often used for hot water supply lines because it can tolerate higher temperatures.
  • PEX (cross-linked polyethylene) tubing is flexible plastic tubing designed for hot and cold water supply. Many plumbers and DIYers prefer PEX over PVC and CPVC because its ability to bend can eliminate the need for elbows in plumbing runs, simplifying the installation process. PEX plumbing lines can be color coded; you use red-tinted PEX for hot water, and blue-tinted tubing for cold water. PEX is also used in radiant floor heating systems.


Copper piping has a long track record in plumbing applications. Rigid copper pipe (usually ½” or ¾” dia.) is typically used for supply lines; larger diameters are used for waste lines. Small-diameter flexible copper pipe is sometimes used to supply coffee makers and ice-making appliances. Fabricating copper plumbing lines calls for fittings that are soldered, although compression-type fittings can also be used in some cases. Copper plumbing can last a long time, but it’s more expensive than plastic, and more susceptible to damage caused by “hard” water, because copper can interact chemically with certain minerals.

Cast iron and lead

These two plumbing pipe materials are no longer used, and for good reason. Cast iron is expensive, heavy, difficult to work with, and prone to deteriorate from rust or corrosion. Lead is also difficult to work with, and its toxicity poses a serious health hazard when lead supply lines are used. If you have an older house that contains cast iron or lead plumbing lines, have any lead supply lines replaced immediately. Cast iron waste lines can be replaced with plastic on an as-needed basis.

Don’t Forget the Fittings

Plumbing requires plenty of fittings. Here are some of the main fittings required in a residential plumbing system:

  • Couplings for joining two sections of pipe
  • Elbows for changing direction
  • Tees for creating branch supply lines
  • Cleanouts for clearing clogged waste lines
  • Valves for shutting off the water supply
  • Transition fittings for joining different materials (like copper and PVC pipe)

Water Heating

Heating water typically accounts for 15% or more of a home’s total energy expenses. Deciding which type of water heater will be best for your household depends on a number of factors: installation cost, energy efficiency (which determines operating cost), maintenance and longevity expectations, and household details that determine daily demands for hot water. Here are your choices:

Tank-type water heaters: Still the most common choice

A tank-type water heater stores hot water in a tank that can range in size from 6 gal. (to serve a single bathroom) to 80 gal. or more.

This type of water heater relies on natural gas, propane, electricity or fuel oil to heat water. When the water temperature inside the tank drops to 115° (F) or so, the heating element will turn on automatically to bring the water back up to the right temperature. This heating cycle repeats whether you are using hot water or not. ENERGY STAR®-rated water heaters have insulation to reduce standby heat loss as the water in the tank “waits” to get used.

Tankless water heaters: No standby heat loss

True to its name, a tankless water heater has no ability to store hot water. When someone turns on a hot water tap, the heating element in a tankless model automatically turns on, and water is heated as it passes through a heat exchanger. Most residential tankless water heaters use natural gas or propane as the heat source. Unlike tank-type water heaters that use energy to keep water warm even when a house is empty, tankless water heaters only use energy on demand (they’re sometimes called “demand heaters.”). Although a tankless water heater can cost twice as much as a tank-type water heater, it’s a wise choice if there are long periods of time with no demand for hot water.

Indirect water heaters: “Free” hot water in wintertime

This type of water heater relies on your whole-house heating system to heat the water you use for washing. During winter months, when your heating system is operating to keep the house warm, an indirect water heating system provides domestic hot water for free. But this energy savings is lost during hot weather, when the heating system has to operate in order to heat water. Indirect water heating systems provide the highest energy savings in cold climates.

Heat pump water heaters: efficient in warmer climates

Some heat pump systems that provide whole-house heating and cooling can also heat water for washing. Whole-house heat pumps that also heat water for washing have been in use for decades. More recently, compact, air-source heat pumps have been used as the heat source for tank-type water heaters. The heat pump unit is installed on top of the hot water storage tank, and the heat pump will automatically turn on when water in the tank falls below a preset temperature. This type of water heater works best in warm and mild climates.

Solar hot water: a cost-saving assist from the sun

Does your house or your property have good solar exposure? If so, you may want to consider a “solar thermal” system. This type of system circulates water or (in cold climates) an anti-freeze solution in a heat exchanger that uses direct sunlight as the heat source. An insulated storage tank holds the solar-heated water. The tank will also have a backup heat source, to bring water up to temperature when solar heating isn’t available. Solar hot water systems have a long track record in the U.S. and around the world. A solar thermal system can cut your water-heating expenses by as much as 80%.

Common Problems

Clogged lines

Clogs usually occur in drain lines, and need to be fixed promptly to avoid damage from a sink or toilet that overflows. Most toilet clogs can be dislodged using a plunger (aka plumber’s helper). Sink clogs typically occur in the P-trap located directly below the sink drain. To clean out a clogged trap, place a bucket beneath the trap and detach the trap by unscrewing two slip nuts. Empty the trapped water in the bucket, clean out the trap, then reassemble your plumbing. Call in a plumber if you can’t locate or dislodge a clog.


Water leaks can cause major damage, but most leaks are preventable. Here are the major causes of leaks in a plumbing system:

  • Leaks around fittings. An improperly made solder joint can leak in copper plumbing lines. Compression or threaded plumbing connections can leak if the connection is loose. To prevent leaks in screwed connections (used on showerheads and flexible supply lines for sinks and toilets), wrap Teflon® plumber’s tape around the threads before attaching the connection nut.
  • Cracked pipe. PVC and CPVC pipe can crack from a hard impact or from water that freezes in the pipe. Copper pipe can crack if water freezes in a pipe run.
  • Faulty valves. Quality can vary in plumbing valves. A good valve can provide leak-free performance for many years, while a poorly made valve will start to leak after frequent use.


Today, the water supply in many areas is more likely to contain impurities that can pose serious health hazards. The good news is that mitigation systems can remove this contamination if they’re installed and maintained properly. Make sure to have your water tested by a water test company. These professionals can recommend the proper treatment to remove specific contaminants.

Excessive water use

Modern plumbing fixtures like toilets and shower-heads are designed to use water more efficiently than older fixtures. Replacing old, water-wasting fixtures with new, more efficient versions will lower your sewer bill (or reduce the load on your septic system), while also protecting the environment. Use the same strategy with your dishwasher and washing machine. New ENERGY STAR models won’t just cut down on your water use; they’ll also help to reduce your electric bill.

Well and septic problems

A house with its own well and septic system requires maintenance and occasional repairs. A septic tank should be pumped at least once a year, and care must be taken not to damage a septic field by running heavy equipment over the field area.

A well can sometimes be contaminated with bacteria. This will show up in a water test. If bacteria are present, the problem can be solved with a chlorine treatment. The well pump that delivers water to a holding tank will eventually require replacement, but this is a standard repair that any plumber can handle.