Plumbing system fundamental and design course Lecture (3) : Design of cold & potable water systems Eng: Ali Widaa Ali

Design of cold & potable water systems Estimation of minimum number of plumbing fixtures for facilities( residential, hotels, schools etc. ) Fixture unites ( water supply & drainage fixture units) Piping materials for water distribution Sizing plumbing water systems

Estimation of minimum number of plumbing fixtures

Water supply Fixture Units A quantity in terms of which the load – producing effects on the plumbing system of different kinds of plumbing fixtures are expressed on some arbitrarily chosen scale.

Water supply demand

Design of hot and cold water system Water storage in the building: Domestic & potable irrigation fire fighting water storage in the building: underground tanks Roof tanks

Storage of water: Water is stored in buildings due to the irregular supply of city water. Normally water is stored in basement with pump transferring water to roof tanks. Roof tanks could one single tank for the whole building or separate tanks for each flat. Water tanks are provided normally with float valve, drain valve, discharge valve, overflow and vent pipe. Roof tanks should be elevated enough above roof level to have enough pressure for the upper apartment, otherwise booster pump is needed.

Sizing plumbing water systems: Common water supply systems Up Feed (direct) water supply system. Down Feed (indirect) water supply system.

Steps for sizing Water supply systems: Daily Water Requirement: Daily water requirement &Tanks capacities is based in the fixture supply units .

Water storage tank

Water storage tank

Water storage tanks Plastic and fiberglass water tank

GRP Water tank

Concrete water tank

Sizing and selection of water storage tank Water storage size = Water supply demand * Water Storing Period

Piping materials for water distribution Galvanized steel pipe Copper Alloy pipe Plastic pipe - CPVC - PPR - HDPE - PEX

Steps for sizing water supply systems The water distribution system shall be designed, and pipe sizes shall be selected such that under conditions of peak demand, the capacities at the fixture supply pipe outlets shall not be less than shown in Table 604.3 .

Size of fixture supply The minimum size of a fixture supply pipe shall be as shown in table 604.5 . The fixture supply pipe shall not terminate more than 30 inches ( 762 mm) from the point of connection to the fixture . A reduced-size flexible water connector installed between the supply pipe and the fixture shall be of an approved type. The supply pipe shall extend to the floor or wall adjacent to fixture

Selection of pipe size Before attempting to size any water supply system, it is necessary to gather preliminary information which includes available pressure, piping material, select design velocity, elevation differences and developed length to most remote fixture. Water pipe sizing procedures are based on a system of pressure requirements and losses, the sum of which must not exceed the minimum pressure available at the supply source. These pressure are as follows:

Pressures Pressure required at fixture to produce required flow. Static pressure loss or gain ( due to head) Loss through water meter. Loss through taps in water main. Losses through special devices such as filters and regulators Loss through valves and fittings. Loss due to pipe friction

Selection of pipe size The objective in designing the water supply system is to ensure an adequate water supply and pressure to all fixtures and equipment. Divide the system into sections breaking at major changes in elevation or where branches lead to fixture groups. Draw draft schematic of the piping from the main line to the all fixtures. Determine from tables and charts:

Selection of Pipe Size 1.The minimum pressure needed in each line. 2. The minimum flow rate needed in each line ( hunter curve or the table) 3. The length of the section. 4. Equivalent length fittings and valves 5. Total equivalent length (3+5) 6. Friction loss per unit of length of trail size of pipe 7. Friction loss in equivalent length (6*5) 8. Excess pressure over friction losses