Plumbing
Plumbing fixtures in most houses are located near
the 3 or 4-inch drain-waste-vent (DWV) pipe. Also known as the main
stack or soil stack; or auxiliary DWV stack. The DWV extends from
the basement floor to the roof, serving as the drain and vent for
multiple fixtures.
Typically, plumbing in residential structures involves not just
a water supply system; it also involves fixtures and a drain system.
It works something like the following:
- Fresh water enters the home through a main supply line. As it
does it usually passes through a meter that registers the amount
of water flowing into the house.
- After entering the home, the water line branches off; some of
the water feeds into a hot water heater. Warmed water from the
heater flows through a line that runs parallel to the cold water
line, feeding fixtures and appliances within the home.
- Waste water from fixtures and appliances flow into a trap, then
into a drainage system that travels downhill through a series
of large-diameter drain pipes.
- The drain pipes are attached to a system of vent pipes that
allow air into the system through a roof vent. This keeps the
drain water flowing properly.
Eventually the drain water reaches a main waste and stack vent that
directs the water into an underground sewer line. This carries the
water away from the house and into a municipal sewer system or a
septic tank.
Supply Pipes
It is the cold and hot water supply pipes that make up the home’s
plumbing system. Before 1950 most supply pipes were made from galvanized
iron. Homes built after 1950 generally used copper or plastic (CPVC)
pipes. Many homeowners use a home renovation as an opportunity to
replace old supply pipes with new.
Supply pipes are manufactured to withstand high water pressure.
They are usually ½-inch to 1-inch in diameter and are joined
with strong, watertight fittings. Valves are used to control the
flow of water.
Water supply systems are generally located inside wall cavities,
or strapped to the undersides of floor joists.
Drain Pipes
Drain pipes carry water out of the house via a DWV system; drain-waste-vent.
This system uses gravity to draw water down vertical pipes and along
a sloping path into a municipal sewer system or septic tank.
Although drain pipes found in older homes are generally made from
copper or lead, pipes in newer homes are made from plastic or cast
iron. Drain pipes are larger than supply pipes; usually 1¼-inches
to 4-inches in diameter.
The curved section in the DWV is called the trap. The trap holds
a supply of standing water. This prevents toxic sewer gases from
entering the home. Every time the drain is used, old standing water
is replaced with new.
Outdoor air is brought into the house by the vent system in the
drain pipes. This lowers pressure in the pipes and helps keep the
water flowing freely. Improperly constructed drain systems can create
drain malfunctions, interfere with toilet flushing, and allow sewer
gas to back up and enter the home.
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