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Design of Water Supply Distribution System

An efficient plumbing system starts with a design that saves water and energy resources. A good design incorporates short runs between plumbing fixtures and uses state-of-the art materials. A plumbing design must include two systems: the system that supplies water and the system that gets rid of waste. Before you begin designing a house for plumbing, drain, waste and vent systems, you must follow local building codes to ensure design compliance.

A Plumbing designer should know the basic plumbing principles and standards of plumbing materials. Avoid any plumbing plans that requires the plumber to weaken the building structure.

Distribution System for a Building: Water is conveyed from the street mains to the individual building, and then to the taps and other fixtures. The supply from the main line to the individual is made through the house service connection.



(a) All pipe, tube, and fittings carrying water used in potable water system intended to supply drinking water shall meet the requirements of NSF 61 as found in Table 14-1.

(b) Materials for building water piping and building supply piping shall be in accordance with Table 6-4 (UPC) and Table 3-4 (NSPC).


PP-R Pipes

CPVC Pipes

PEX Pipes

Pipe Identification:

(a) Potable Water : Green background with white lettering

(b) Non-Potable Water: Yellow background with black lettering, with the words " Caution: Non-Potable water, do not drink".

Backflow Prevention:
(a) When a backflow occurs, it can pollute entire water systems. Without a backflow and back siphonage protection, municipal water services could become contaminated.

(b) Backflow prevention can be done using Airgap, Atmospheric Vacuum Breaker (AVB), Hose connection backflow preventer, Double check valve backflow prevention assembly(DC), Pressure vacuum breaker backflow prevention assembly (PVB) etc.

(c) An air gap is the most positive form of protection from backflow.

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Air Gap Backflow Preventer

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Double Check Valve Backflow Preventer

Atmospheric Vacuum Breaker
Water closet and urinal flushometer valves shall be equipped with an atmospheric vacuum breaker. The vacuum breaker shall be installed on the discharge side of the flushometer valve with the critical level at least 6".

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Water closet and urinal tanks shall be equipped with a ballcock. The ballcock shall be installed with the critical level at least 1" above the full opening of the overflow pipes. 


Separation of Water Service and Building Sewer
The water service pipe and building drain shall not have less than one foot horizontal distance between the piping. 


Water Service Near Source of Pollution

Potable water service piping shall not be located in, under, or above septic tanks or drainage pits. A separation of 10 feet shall be maintained from such systems. When a water line parallels or crosses over or under a sewer, a minimum clearance of 12 inches in all directions shall be maintained.


The water service piping and distribution piping to all fixtures and outlets shall be flushed until the water runs clear and free of debris or particles. Faucet aerators or screen shall be removed during flushing operations.


Water service piping and the hot and cold water distribution piping in new or renovated potable water systems shall be disinfected after flushing and prior to use. The procedure used shall be as follows or an approved equivalent:

Building Valve (Isolation Valve)

The building water service shall be provided with a readily accessible Gate Valve. When there are two or more water services serving one building, a check valve shall be installed on each service in addition to the above valves. 


Pressure Reducing Valves

Where static water pressure in the water supply piping is in excess of 80 psi (552 kPa), an approved type pressure reducing valve by an adequate strainer shall be installed and the static pressure reduced to 80 psi or less. 


Hose Connection

A pressure type or atmospheric type vacuum breaker or a permanently attached hose connection vacuum breaker shall protect hose bibs, sill-cocks, wall hydrants opening with a hose connections.

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Stop-and-Waste Valve Prohibited

Combination stop-and-waste valve or cocks shall not be installed underground in water serving piping.

Water Service Pipes Sleeves

Pipe sleeves shall be provided where water services pipes penetrate foundation walls or floors. Slab to be protected against corrosion of pipe and allow clearance for expansion, contraction and settlement. The annular space between the pipe and the sleeve shall be resiliently sealed watertight.


Water Pressure Booster Systems

(a) When the water pressure in the public water main or individual water supply system is insufficient to supply the potable peak demand flow to plumbing fixtures and continuously with minimum pressure, the rate of supply shall be supplemented by one of the following:
       1. An elevated water tank
       2. An hydro-pneumatic pressure booster system
       3. A water pressure booster pump.


Water Tanks

A   water tower   is an elevated structure supporting a   water tank   constructed at a height sufficient to pressurize a   water distribution system   for the distribution of   potable water .
Water towers are able to supply water even during power outages, because they rely on   hydrostatic pressure   produced by elevation of water (due to   gravity ) to push the water into domestic and industrial water distribution systems; however, they cannot supply the water for a long time without power, because a pump is typically required to refill the tower. A water tower also serves as a reservoir to help with water needs during peak usage times. The water level in the tower typically falls during the peak usage hours of the day, and then a pump fills it back up during the night. This process also keeps the water from freezing in cold weather, since the tower is constantly being drained and refilled.

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Pressurized Water Tanks

A pressure tanks creates water pressure by using compressed air to bear down on water. When a valve is opened, water is pushed out by the compressed air in the tank. The water is pushed throughout the plumbing in the house until the pressure drops to a preset low on pressure switch. All pressurized water tanks should be equipped with a vacuum relief valve at the top of the tank. These vacuum relief valve shall be rated for maximum temperature of 200° F and maximum pressure of 200 psi.
It is also necessary to equip these tanks with pressure-relief valves. These safety valves must be installed on the supply pipe that feeds the tank or on the tank, itself.

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A Water Pressure Booster Pump

A booster pump increases low water pressure and flow. It provides the extra boost needed to bring your water pressure to the desired level. A water booster pump provides pressure to move water from a storage tank or throughout a whole house or commercial facility.
Booster pumps increase low water flow in water systems or industrial equipment and transport water from a lake, pond, or storage tank for use in a home or commercial building. A household that doesn't receive enough pressure from the city water supply would need a pump to increase low water pressure. A hotel needs a large commercial booster pump to send water all the way to the top story.  
A booster pump is also used to re-pressurize water from a storage tank and send it to a faucet or throughout a home. In a rain harvesting system, for example, water collects in a storage tank. In order to use it to flush toilets or wash laundry, the water must be pumped out of the tank and into the house. You would use a booster pump to move the water.


Water Hammer

Water hammer in a pipeline is caused by a sudden stoppage of flow and is characterized by loud noise and vibration. The formula expressing the relationship between pressure.
All building supply systems in which quick-acting valves are installed shall be provided with devices to absorb the hammer caused by high pressure resulting from the quick closing of these valves. Water pressure absorbing devices shall be installed as close as possible to quick acting valves.


Valve Regulations

Gate and ball valves are examples of full open valves as required under valve regulations. These valves may be required in the following locations:
        a. On the water service before and after the water meter.
        b. On each water service for each building served.
        c. On discharge pipes of water supply tanks near the tank.
        d. On the supply pipe to every water heater near to the heater.
        e. On the main supply pipe to each dwelling / toilets.
        f. On water supplies to pressurized tanks, such as well system


Hot Water Supply System

a) In residences and building intended for human occupancy, hot water shall be supplied to all plumbing fixtures and equipment's used for bathing, washing, laundry or building maintenance.

b) If the distance between the hot water source and the fixture being served is more than 100 feet, a re-circulating system is required.

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Hot Water Storage Tanks
a) Water heaters and storage tanks shall be sized to provide sufficient hot water to provide both daily requirements and hourly peak loads of the occupants of the buildings.

b) Storage tanks shall be protected against excessive temperature and pressure conditions.

c) Hot water storage tanks shall be equipped with a valve capable of draining the tank completely.

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