Engineering part 4

Plumbing is the skilled trade of working with pipes, tubing and plumbing fixtures for drinking water systems and the drainage of waste. The plumbing industry is a basic and substantial part of every developed economy due to the need for clean water, and proper collection and transport of wastes. Plumbing also refers to a system of pipes and fixtures installed in a building for the distribution of potable water and the removal of waterborne wastes. Plumbing is usually distinguished from water and sewage systems. It also includes the fire escape plan.

Firestopping is required where mechanical penetrants traverse fire-resistance rated wall and floor assemblies, or membranes thereof. This work is usually done worldwide by the insulation trade and specialty firestop sub-contractors.

A building's waste-disposal system has two parts: the drainage system and the venting system. The drainage system, also called traps and drains, comprises pipes leading from various plumbing fixtures to the building drain (indoors) and then the building sewer (outdoors). The building sewer is then connected to a municipal sanitary sewage disposal system. Where connection to a municipal sewage system is not possible, a local, private, code-approved septic system is required.

The venting system, also called plumbing vents, consists of pipes leading from fixtures to the outdoors, usually via the roof. Vents provide for relief of sewer gases, admission of oxygen for aerobic sewage digestion, and maintenance of the trap water seals which prevent sewer gases from entering the building. Every fixture is required to have an internal or external trap; double trapping is prohibited by plumbing codes. With exceptions, every plumbing fixture must have an attached vent.

Plumbing drainage and venting systems maintain neutral air pressure in the drains, allowing flow of water and sewage down drains and through waste pipes by gravity. As such, it is critical that a downward slope be maintained throughout. In relatively rare situations, a downward slope out of a building to the sewer cannot be created, and a special collection pit and grinding lift 'sewage ejector' pump are needed.

The septic tank is a small scale sewage treatment system common in areas with no connection to main sewage pipes provided by private corporations or local governments. (Other components, typically mandated and is restricted by local governments, optionally include pumps, alarms, sand filters, and clarified liquid effluent disposal means such as a septic drain field, ponds, or peat moss beds.) Septic systems are a type of On-Site Sewage Facility (OSSF).

Drainage is the natural or artificial removal of surface and sub-surface water from an area. Many agricultural soils need drainage to improve production or to manage water supplies.