Residential Plumbing System: All You Need to Know!

Civil Engineer / Content Writer

Water is an essence of life. Civilizations have grown where water was available like on the bank of the river. Water is necessary to carry out various household activities in day to day life.  Hence, water service (i.e. water supply and drainage) has become an integral part of any house construction. The provision of water services in a house is known as a residential plumbing system. It is complicated and one of the costliest system to install and repair. This article briefs about house plumbing system, which will be of great help to understand its design, purpose, working and maintenance.

The residential plumbing system is a complex network comprises of hot & cold water supply pipes, fixtures and appliances, drain pipes, traps, vent pipes, water storage tanks, etc. It runs either unseen inside the walls or on the walls.

Objectives of Good Plumbing System are:

  • Supplying safe drinking water (potable water) in adequate quantities at the right pressure and in the right quantity.
  • Check on leakages to minimise wastage of water or say zero leakage.
  • In no case, potable water should get mixed with wastewater.
  • Collecting and disposing wastewater from house efficiently.
  • Preventing entry of foul gases in the home and allowing its easy escape.
  • Drain pipe from the house should have access towards sewer lines or septic tank with a downward slope, minimum of a 1/4th inch per foot slope, i.e. 20mm per 1m and maximum of 3inch per foot, i.e. 80mm per 1m.
  • Provision of manholes for cleaning of drain pipes.
  • Plumbing appliances, materials and workmanship should conform to quality standards.

Three Essential Parts of Residential Plumbing System are:

  • Water Supply System (flow of water into a house)
  • Fixtures and Appliances (where water used for carrying out various activities)
  • Drainage system (collection and disposal of used (waste) water)
Courtesy – Plumbing and Piping Diagram

Blue signifies cold water supply

Red signifies hot water supply

Green signifies drain system

Yellow signifies vent (air) system

Working of Residential Plumbing System:

(a) Water Supply System :

01. Potable water is supplied by the municipality or private water company or through private underground bore well.

02. This water enters a house through main supply line (aka mains). Water supply in a house is either of direct water supply system or indirect water supply system. The design of water supply system network will depend on whether supply is 24 x 7 or intermittent.

  • Direct Water Supply System: All water outlets of a house receive water directly from the mains. Potable water is available at all faucets. This is possible where water source delivers water 24 x 7 with high water pressure, sufficient enough to deliver water at an adequate pressure at all faucets (taps).
  • Indirect Water Supply System: Water from mains is conveyed to storage water tanks. Water is then delivered to house from water storage tank. This system is adopted where water supply from mains is not available throughout the day. It is also used when water pressure in mains is not sufficient enough to deliver water at all faucets with adequate pressure.

03. Main supply line (down take pipe in case of Indirect water supply system) then splits into two branch lines. One branch line takes water to water heater and other branch line carries cold water.

04. From water heater, hot water line runs parallel to the cold water line. Both lines bring water at fixtures and appliances throughout the house.

05. Thus, it is basically a network of pipes for distribution and delivery of water.

06. Underground and overhead tank and pumping of water also needs careful consideration.

07. Sometimes booster pumps are also installed so as to deliver water at uniform and adequate pressure.

(b) Fixtures and Appliances:

01. Various sanitary fixtures and appliances are provided in house.

  • Fixtures: sinks, bathtubs, showers and laundry tubs (toilets and exterior sillcocks (bibs) requires only cold water line)
  • Appliances: water heaters, dishwashers, washing machine, water softeners

02. All fixtures and appliances require water at distinct water pressure and water flow. Pressure at fixtures and appliances should not be less than 1.2kg/cm² (12m head) and not greater than 5kg/cm² (50m head). Care should be taken while fixing height of fixtures so that adequate water pressure is available.

03. Water outlet at fixtures and appliances is controlled by faucets (taps) and valves.

04. Nowadays sophisticated faucets are available needing basic minimum pressure and for which sound hydraulic design is must.

(c) Drainage or Waste Water Disposal:

01. The used water then enters drainage system (wastewater system).

02. Before entering drainage pipes, used water is first passed through drain traps.

  • Trap: It is a U-shaped pipe. It holds standing water and prevents foul sewer gases from entering and spreading into room space.

03. Drainage system works entirely on gravity. All the wastewater flows downward through a series of large diameter pipes.

04. The drainage pipes are attached to a system of vent pipes.

  • Vent pipe: Vent pipes are open from the top end, from where they bring fresh air to the drain system, forcing drainage water to flow downward. These pipes exit house at rooftop.

05. All wastewater eventually reaches main wastewater line, which exits the house and is connected to either municipal sewer line or connected to the septic tank and cesspit where the sewer line is not available.

In case of a drainage system, the invert levels of inspection chambers or manhole on road are very important for gravity flow. Apart from above rainwater drainage and fire protection system also form part of modern houses.

Also Read:

Domestic Water Supply System
Direct vs Indirect Water Supply System
Hot Water Supply System
Types of Traps

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