Plumbing Terms around your Home Explained

Plumbing may be defined as the practice, materials and fixtures used  in the installation, maintenance and alteration of all piping, fixtures,  appliances and appurtenances in connection with sanitary and storm drainage  facilities, the venting system, and public and private water supply systems.  Plumbing does not include the trade of drilling water wells, installing  water-softening equipment, or the business of manufacturing or selling plumbing  fixtures, appliances, equipment or hardware. A plumbing system consists of three  separate parts: an adequate potable water supply system; a safe, adequate  drainage system; and ample fixtures and equipment.
Background Factors
The generalized inspection of a home is concerned with a safe  water supply system, an adequate drainage system, and ample and proper fixtures  and equipment. This article explains features of a residential plumbing system,  and the basic plumbing terms the inspector must know and understand to properly  identify housing code violations involving plumbing and the more complicated  defects that s/he will refer to the appropriate agencies. Only InterNACHI  inspectors are sufficiently trained to spot complicated defects that others will  overlook.
Air Chambers
Pressure absorbing devices that eliminate water hammer. They should  be installed as close as possible to the valves or faucet and at the end of long  runs of pipe.
Air Gap (Drainage System)
The unobstructed vertical distance through the free atmosphere  between the outlet of a water pipe and the flood level rim of the receptacle  into which it is discharging.
Air Gap (Water Distribution System)
The unobstructed vertical distance through the free atmosphere  between the lowest opening from any pipe or faucet supplying water to a tank,  plumbing fixture, or other device and the flood level rim of the  receptacle.
Air Lock
An air lock is a bubble of air which restricts the flow of water in a  pipe.
The flow of water or other liquids, mixtures, or substances into the  distributing pipes of a potable water supply from any source or sources other  than the intended source. Back siphonage is one type of backflow.
Back Siphonage
The flowing back of used, contaminated, or polluted water from a  plumbing fixture or vessel into a potable water supply due to a negative  pressure in the pipe.
Any part of the piping system other than the main, riser, or  stack.
Branch Vent
A vent connecting one or more individual vents with a vent  stack.
Building Drain
The part of the lowest piping of a drainage system that receives the  discharge from soil, waste, or other drainage pipes inside the walls of the  building (house) and conveys it to the building sewer beginning 3 feet outside  the building wall.
Cross Connection
Any physical connection or arrangement between two otherwise separate  piping systems, one of which contains potable water and the other either water  of unknown or questionable safety or steam, gas, or chemical whereby there may  be a flow from one system to the other, the direction of flow depending on the  pressure differential between the two systems. (See Backflow and Back  siphonage.)
Disposal Field
An area containing a series of one or more trenches lined with coarse  aggregate and conveying the effluent from the septic tank through vitrified clay  Pine or perforated, non-metallic pipe, laid in such a manner that the flow will  be distributed with reasonable uniformity into natural soil.
Any pipe that carries waste water or water-borne waste in a building  (house) drainage system.
Flood Level Rim
The top edge of a receptacle from which water overflows.
Flushometer Valve
A device that discharges a predetermined quantity of water to  fixtures for flushing purposes and is closed by direct water pressures.
Flush Valve
A device located at the bottom of the tank for flushing water closets  and similar fixtures.
Grease Trap
See Interceptor.
Hot Water
Potable water that is heated to at least 120°F and used for cooking,  cleaning, washing dishes, and bathing.
Contrary to sanitary principles injurious to health.
A device designed and installed so as to separate and retain  deleterious, hazardous, or undesirable matter from normal wastes and permit  normal sewage or liquid wastes to discharge into the drainage system by gravity.
An exterior drainage pipe for conveying storm water from roof or  gutter drains to the building storm drain, combined building sewer, or other  means of disposal.
Main Vent
The principal artery of the venting system, to which vent branches  may be connected.
Main Sewer
See Public Sewer.
The word pertains to devices making use of compressed air as in  pressure tanks boosted by pumps.
Potable Water
Water having no impurities present in amounts sufficient to cause  disease or harmful physiological effects and conforming in its bacteriological  and chemical quality to the requirements of the Public Health Service drinking  water standards or meeting the regulations of the public health authority having  jurisdiction.
P & T (Pressure and Temperature) Relief Valve
A safety valve installed on a hot water storage tank to limit  temperature and pressure of the water.
P Trap
A trap with a vertical inlet and a horizontal  outlet.
Public Sewer
A common sewer directly controlled by public  authority.
Relief Vent
An auxiliary vent that permits additional circulation of air in or  between drainage and vent systems.
Septic Tank
A watertight receptacle that receives the discharge of a building’s  sanitary drain system or part thereof and is designed and constructed so as to  separate solid from the liquid, digest organic matter through a period of  detention, and allow the liquids to discharge into the soil outside of the tank  through a system of open-joint or perforated piping, or through a seepage  pit.
Sewerage System
A sewerage system comprises all piping, appurtenances, and treatment  facilities used for the collection and disposal of sewage, except plumbing  inside and in connection with buildings served and the building drain.
Soil Pipe
The pipe that directs the sewage of a house to the receiving sewer,  building drain, or building sewer.
Soil Stack
The vertical piping that terminates in a roof vent and carries off  the vapors of a plumbing system.
Stack Vent
An extension of a solid or waste stack above the highest horizontal  drain connected to the stack. Sometimes called a waste vent or a soil  vent.
Storm Sewer
A sewer used for conveying rain water, surface water, condensate.  cooling water, or similar liquid waste.
A trap is a fitting or device that provides a liquid seal to prevent  the emission of sewer gases without materially affecting the flow of sewage or  waste water through it.
Vacuum Breaker
A device to prevent backflow (back siphonage) by means of an opening  through which air may be drawn to relieve negative pressure  (vacuum).
Vent Stack
The vertical vent pipe installed to provide air circulation to and  from the drainage system and that extends through one or more  stories.
Water Hammer
The loud thump of water in a pipe when a valve or faucet is suddenly  closed.
Water Service Pipe
The pipe from the water main or other sources of potable water supply  to the water-distributing system of the building served.
Water Supply System
The water supply system consists of the water service pipe, the  water-distributing pipes, the necessary connecting pipes, fittings, control  valves, and all appurtenances in or adjacent to the building or premises.
Wet Vent
A vent that receives the discharge of waste other than from water  closets.
Yoke Vent
A pipe connecting upward from a soil or waste stack to a vent stack  for the purpose of preventing pressure changes in the stacks.
Main Features of an Indoor Plumbing  System
The primary functions of the plumbing system within the house are  as follows:

  1. To bring an adequate and potable supply of hot and cold water to the  users of the dwelling.
  2. To drain all waste water and sewage discharged from these fixtures  into the public sewer, or private disposal system.

It is,  therefore, very important that the housing inspector familiarize himself fully  with all elements of these systems so that he may recognize inadequacies of the  structure’s plumbing as well as other code violations.

Elements of a Plumbing System
Water Service: The piping of a house service line should be as  short as possible. Elbows and bends should be kept to a minimum since these  reduce the pressure and therefore the supply of water to fixtures in the house.  The house service line should also be protected from freezing. The burying of  the line under 4 feet of soil is a commonly accepted depth to prevent freezing.  This depth varies, however, across the country from north to south. The local or  state plumbing code should be consulted for the recommended depth in your area  of the country.   The materials used for a house service may be  copper, cast iron, steel or wrought iron. The connections used should be  compatible with the type of pipe used.

  • Corporation stop:  The corporation stop is connected to the water  main. This connection is usually made of brass and can be connected to the main  by use of a special tool without shutting off the municipal supply. The valve  incorporated in the corporation stop permits the pressure to be maintained in  the main while the service to the building is completed.
  • Curb stop:  The curb stop is a similar valve used to  isolate the building from the main for repairs, nonpayment of water bills, or  flooded basements. Since the corporation stop is usually under the street and  would necessitate breaking the pavement to reach the valve, the curb stop is  used as the isolation valve.
  • Curb stop box:  The curb stop box is an access box to the curb  stop for opening and closing the valve. A long-handled wrench is used to reach  the valve.
  • Meter stop:  The meter stop is a valve placed on the street side  of the water meter to isolate the meter for installation or maintenance. Many  codes require a gate valve on the house side of the meter to shut off water for  house plumbing repairs. The curb and meter stops are not to be used frequently  and can be ruined in a short time if used very frequently.
  • Water meter:  The water meter is a device used to measure the  amount of water used in the house. It is usually the property of the city and is  a very delicate instrument that should not be abused. Since the electric  system is usually grounded to the water line, a grounding loop-device should be  installed around the meter. Many meters come with a yoke that maintains  electrical continuity even though the meter is removed.

Hot and Cold Water Main Lines: The hot and cold water main lines  are usually hung from the basement ceiling and are attached to the water meter  and hot-water tank on one side and the fixture supply risers on the other. These  pipes should be installed in a neat manner and should be supported by pipe  hangers or straps of sufficient strength and number to prevent sagging. Hot and  cold water lines should be approximately 6 inches apart unless the hot water  line is insulated. This is to insure that the cold water line does not pick up  heat from the hot water line. The supply mains should have a drain valve or stop  and waste valve in order to remove water from the system for repairs. These  valves should be on the low end of the line or on the end of each fixture riser.
The fixture risers start at the basement main and rise vertically to the  fixtures on the upper floors. In a one-family dwelling, riser branches will  usually proceed from the main riser to each fixture grouping. In any event the  fixture risers should not depend on the branch risers for support but should be  supported with a pipe bracket. Each fixture is then connected to the branch  riser by a separate line. The last fixture on a line is usually connected  directly to the branch riser.
Hot Water Heaters: Hot water heaters are  usually powered by electricity, fuel oil, gas, or in rare cases, coal or wood.  They consist of a space for heating the water and a storage tank for providing  hot water over a limited period of time. All hot water heaters should be fitted  with a temperature-pressure relief valve no matter what fuel is used. This valve  will operate when either the temperature or the pressure becomes too high due to  an interruption of the water supply or a faulty thermostat.
Pipe Sizes:  The size of basement mains and risers depends on the number of fixtures  supplied. However, a 3/4-inch pipe is usually the minimum size used. This allows  for deposits on the pipe due to hardness in the water and will usually give  satisfactory volume and pressure.

Drainage System
The water supply brought into the house and used is  discharged through the drainage system. This system is either a sanitary  drainage system carrying just interior waste water or a combined system carrying  interior waste and roof runoff.
Sanitary Drainage System: The proper sizing of the sanitary drain or  house drain depends on the number of fixtures it serves. The usual minimum size  is 6 inches in dial diameter. The materials used are usually cast iron,  vitrified clay, plastic, and in rare cases, lead. For proper flow in the drain  the pipe should be sized so that it flows approximately one-half full. This  ensures proper scouring action so that the solids contained in the waste will  not be deposited in the pipe.

  • Sizing of house drain – The Uniform Plumbing Code Committee has  developed a method of sizing of house drains in terms of “fixture units.” One  ”fixture unit” equals approximately 71 D2 gallons of water per minute. This is  the surge flow-rate of water discharged from a wash basin in 1 minute. All other  fixtures have been related to this unit.

Sanitary  Drain Sizes

  • Grade of house drain – A house drain or building sewer should be  sloped toward the sewer to ensure scouring of the drain. The usual pitch of a  house or building sewer is 1 D4 inch fall in 1 foot of length.
  • Fixture and branch drains – A branch drain is a waste pipe that  collects the waste from two or more fixtures and conveys it to the building or  house sewer. It is sized in the same way as the house sewer, taking into account  that all water closets must have a minimum 3-inch diameter drain, and only two  water closets may connect into one 3-inch drain.

All  branch drains must join the house drain with a “Y” -type fitting. The same is  true for fixture drains joining branch drains. The “Y” fitting is used to  eliminate, as much as possible, the deposit of solids in or near the connection.  A build-up of these solids will cause a blockage in the drain.

  • Traps – A plumbing trap is a device used in a waste system to prevent  the passage of sewer gas into the structure and yet not hinder the fixture’s  discharge to any great extent. All fixtures connected to a household plumbing  system should have a trap installed in the line.

The  effect of sewer gases on the human body are known; many are extremely harmful.  Additionally, certain sewer gases are explosive. A trap will prevent these gases  from passing into the structure. The depth of the seal in a trap is usually 2  inches. A deep seal trap has a 4-inch seal.

The purpose of a trap is to seal out sewer gases from the structure.  Since a plumbing system is subject to wide variations in flow, and this flow  originates in many different sections of the system, there is a wide variation  in pressures in the waste lines. These pressure differences tend to destroy the  water seal in the trap. To counteract this problem mechanical traps were  introduced. It has been found, however, that the corrosive liquids flowing in  the system corrode or jam these mechanical traps. It is for this reason that  most plumbing codes prohibit mechanical traps.
There are many manufacturers of traps, and all have varied the design  somewhat. The “P” trap is usually found in lavatories, sinks, urinals, drinking  fountains, showers, and other installations that do not discharge a great deal  of water.
Drum trap
The drum trap is another water seal-type trap. They are usually used  in the 4×5-inch or 4×8-inch sizes. These traps have a greater sealing capacity  than the “P” trap and pass large amounts of water quickly. Drum traps are  commonly connected to bathtubs, foot baths, sitz baths, and modified shower  baths.
Objectionable traps
The “S” 1 and the 3h “S” trap should not be us in plumbing  installations. They are almost impossible to ventilate properly, and the 3h “S”  trap forms a perfect siphon. The bag trap, an extreme form of “S” trap, is  seldom found.
Any trap that depends on a moving part for its  effectiveness is usually inadequate and has been prohibited by the local  plumbing codes. These traps work, but their design usually results in their  being higher priced than the “P” or drum traps. It should be remembered that  traps are used only to prevent the escape of sewer gas into the structure. They  do not compensate for pressure variations. Only proper venting will eliminate  pressure problems.
A plumbing system is ventilated to prevent trap seal loss, material  deterioration. and flow retardation.
Trap Seal  Loss
The seal in a plumbing trap may be lost due to siphonage (direct and  indirect or momentum), back pressure, evaporation, capillary attraction, or wind  effect. The first two named are probably the most common causes of loss. If a  waste pipe is placed vertically after the fixture trap, as in an “S” trap, the  waste water continues to flow after the fixture is emptied and clears the trap.  This is caused by the pressure of air on the fixture water’s being greater than  the pressure of air in the waste pipe. The action of the water discharging into  the waste pipe removes the air from that pipe and thereby causes a negative  pressure in the waste line. In the case of indirect or momentum siphonage, the  flow of water past the entrance to a fixture drain in the waste pipe removes air  from the fixture drain. This reduces the air pressure in the fixture drain, and  the entire assembly acts as an aspirator such as the physician uses to spray an  infected throat.
Back Pressure
The flow of water in a soil pipe varies according to the fixtures  being used. A lavatory gives a small flow and a water closet a large flow. Small  flows tend to cling to the sides of the pipe, but large ones form a slug of  waste as they drop. As this slug of water falls down the pipe the air in front  of it becomes pressurized. As the pressure builds it seeks an escape point. This  point is either a vent or a fixture outlet. If the vent is plugged or there is  no vent, the only escape for this air is the fixture outlet. The air pressure  forces the trap seal up the pipe into the fixture. If the pressure is great  enough the seal is blown out of the fixture entirely. Figures 6-17 and 6-18  illustrate this type of problem.
Vent  Sizing
Vent pipe installation is similar to that of soil and waste pipe. The  same fixture unit criteria are used. Vent pipes of less than 11 D4 inches in  diameter should not be used. Vents smaller than this diameter tend to clog and  do not perform their function.
  • Individual fixture ventilation:  This type of ventilation is  generally used for sinks, lavatories, drinking fountains, and so  forth
  • Unit venting:  The unit venting system is commonly used in  apartment buildings. This type of system saves a great deal of money and space  when fixtures are placed back to back in separate  apartments.
  • Wet venting:  Wet venting of a plumbing system is common in  household bathroom fixture grouping. It is exactly what the name implies: the  vent pipe is used as a waste line.
Total Drainage System
Up to now we have covered the drain, soil waste, and vent systems of  a plumbing system separately. For a working system, however, they must all be  connected.

From  (InterNACHI)