WATER DEMAND (Chapter 24) Types of demand Average daily demand Building type Types of plumbing fixtures Hours of operation Measured in gallons per person per day Peak demand Demand during critical periods of the day Maximum momentary demand Demand by individual plumbing fixtures Measured in gallons per minute

WATER DISTRIBUTION Municipal street main Static pressure (static head) Depth 2 – 7 ft. from grade Pressure ranges from 50 to 70 psi Usually adequate for lowrise buildings Static pressure (static head) Pressure exerted by water standing in vertical piping Pressure exerted by a 1-sq. in. column of water, 1 ft. in height = 0.433 psi

WATER DISTRIBUTION Upfeed distribution Downfeed distribution Simple upfeed Water fed to fixtures in a building only by the incoming pressure of the supply water. This method is good for buildings up to 5 to 6 stories high. Pumped upfeed Water fed to the fixtures in a building by increasing the pressure of the supply water using additional pumps. Hydro-pneumatic upfeed Downfeed distribution Uses pumps to deliver water to a rooftop storage tank of the building. The water in the storage tank feeds fixtures below due to the force of gravity. Cross-connection and backflow Connection between supply system and any system containing non-potable water Backflow prevention Air gap Atmospheric Vacuum breaker Pressure Vacuum breaker

SUPPLY PIPING MATERIALS (Chapter 24) Steel and galvanized steel Copper Plastic Water supply accessories and controls Valves Gate valve Globe valve Check valve Ball valve Butterfly valve Water hammer arrestor Insulation Pipe expansion Pipe support

SUPPLY PIPING MATERIALS (Chapter 24)(Additional information) Need for piping To transport water from source to the locations of use Requirements Efficient Low maintenance Non-corrosive

SUPPLY PIPING MATERIALS (Chapter 24) Steel: inexpensive, used only where water is non-corrosive Brass, red: expensive, corrosion resistant to a certain extent Copper: Less expensive than brass, corrosion resistant Plastic: Corrosion resistant, special types required for hot water Galvanized steel: Moderately corrosion resistant

SIZING OF SUPPLY PIPES Some definitions (additional information) Fixture pressure : Pressure required to operate a fixture; varies from 5 to 15 psi PSI: pound(s) per square inch gpm: gallon(s) per minute Fixture unit: An index of water demand by a fixture DL: Actual linear distance of pipe from street main to the remotest fixture EL: Additional length of piping (in terms of friction loss) equivalent to fittings, 50% of DL TEL: Total Equivalent Length, DL+EL Static pressure: Pressure loss due to height (Height*0.433)

SIZING OF SUPPLY PIPES Pressure components in an upfeed supply system Pflh = Pressure loss due to friction in piping Psm = Street or municipal main pressure Pf = Pressure required to operate a fixture (use the highest figure) Pht = Pressure loss due to height (static pressure): 0.433 psi/ft. Pm = Pressure loss due to water flow through meter (Pflh+Pf+Pht+Pm) should be equal to Psm Friction loss equation Pflh/100 = [Psm-(Pf+Pht+Pm)]*100/TEL

SIZING OF SUPPLY PIPES Total water demand Pipe size Calculated in gpm using Hunter's curve (or the algorithm provided by the instructor) Curve 1 (if Hunter's curve is used) to be used if there is any FV operated fixture in the system Curve 2 (if Hunter's curve is used) to be used, if otherwise Demand for hot and cold supply to be calculated separately Pipe size To be determined using the sizing graph or By using this formula: Pf = (4.52*Q1.85)/C1.85*ð4.87) Both friction loss and demand calculations will be required to find sizes Velocity of water in supply pipes Should not exceed 10 fps Pipe size should be increased if velocity exceeds this limit

PRESSURE TANK (Additional information) Sizing pressure tank: Q = Qm/[1-(P1/P2)] Q = tank volume (gal) Qm = 15 minutes of storage at peak usage rate (gal) P1 = min. allowable operating pressure + 14.7 psi P2 = max. allowable operating pressure + 14.7 psi The additional 14.7 psi added to maximum and minimum operating pressures of fixtures is atmospheric pressure. The sum of gauge pressure in the pumping system and atmospheric pressure is called absolute pressure.