Water Siphonage Environmental Engineering

a Per day of operation

Note: The table remains unchanged in the latest ASHRAE publication—2007 ASHRAE Handbook: HVAC Applications. Heaters should be preset to deliver water at 130°F (54°C). The Consumer Product Safety Commission (CPSC) recommends a maximum of 120°F (49°C). Source: ASHRAE Guide and Data Book, Atlanta, GA, 1970. Copyright by the American Society of Heating, Refrigerating and Air Conditioning Engineers. Inc. Reprinted with permission.

a Per day of operation

Note: The table remains unchanged in the latest ASHRAE publication—2007 ASHRAE Handbook: HVAC Applications. Heaters should be preset to deliver water at 130°F (54°C). The Consumer Product Safety Commission (CPSC) recommends a maximum of 120°F (49°C). Source: ASHRAE Guide and Data Book, Atlanta, GA, 1970. Copyright by the American Society of Heating, Refrigerating and Air Conditioning Engineers. Inc. Reprinted with permission.

fixtures, the application of indirect waste piping, and other details are discussed below.

Backflow Prevention

The backflow of polluted or contaminated water or other fluid or substance into a water distribution piping system through back pressure or back siphonage is a very real possibility. The best way to eliminate the danger is to prohibit any connections between the water system and any other system, fixture vat, or tank containing polluted or questionable water. This can be accomplished by terminating the water supply inlet or faucet a safe distance above the flood-level rim of the fixture. The distance, referred to as the air gap is 1 inch for a 0.5-inch-or-smaller-diameter faucet or inlet pipe, 1.5 inches for a 0.75-inch-diameter faucet, 2 inches for a 1-inch-diameter faucet, and twice the effective opening (cross-sectional area at point of water supply discharge) when its diameter is greater than 1 inch. When the inside edge of the faucet or pipe is close to a wall—that is, within three or four times the diameter of the effective opening—the air gap should be increased by 50 percent.

Sometimes, as with water closets and urinals equipped with flushometer valves, it is not possible or practical to provide an air gap. Under such circumstances, where the water connection is not subject to back pressure, an approved nonpressure-type backflow preventer, such as that shown in Figure 2.13, may be used to prevent back siphonage. The backflow preventer

To water closet To water closet

FIGURE 2.13 Vacuum, nonpressure-type siphon-breakers: (a), (b), (c) Moving parts; (d) Nonmoving part. Installed after fixture valve. (Source: R. B. Hunter, G. E. Golden, and H. N. Eaton, "Cross-Connections in Plumbing Systems," Research Paper RP 1086, J. Res. Natl. Bur. Stand., 20 (April 1938).)

To water closet To water closet

FIGURE 2.13 Vacuum, nonpressure-type siphon-breakers: (a), (b), (c) Moving parts; (d) Nonmoving part. Installed after fixture valve. (Source: R. B. Hunter, G. E. Golden, and H. N. Eaton, "Cross-Connections in Plumbing Systems," Research Paper RP 1086, J. Res. Natl. Bur. Stand., 20 (April 1938).)

must be installed on the outlet side of the control valve, at a distance not less than four times the nominal diameter of the inlet, measured from the control valve to the flood-level rim of the fixture, and in no cases less than 4 inches.

A pressure-type vacuum breaker (see Figure 2.14) is installed on a pressurized system and will function only when a vacuum occurs. It should not be installed where backpressure may occur. Figure 2.14 also shows a hose bib vacuum breaker and an atmospheric vacuum breaker.

(6) Pressure Vacuum Breaker

(Installed 5 to 12 ;r higher than outlet)

(a) Hose Bibb Vacuum Breaker

(6) Pressure Vacuum Breaker

(Installed 5 to 12 ;r higher than outlet)

(a) Hose Bibb Vacuum Breaker

Flow condition Nonflow condition

(c) Atmospheric Vacuum Breaker

FIGURE 2.14 Vacuum breakers: (a) Generally attached to sill cocks and, in turn, are connected to hose supplied outlets such as garden hoses, slop sink hoses, and spray outlets, (b) A spring on top of the disc and float assembly, two added gate valves, test cocks, and an additional first check make possible its utilization under constant pressure, (c) Must be installed vertically, must not have shutoffs downstream, and must be installed at least 6 in. higher than the final outlet. (Source: Cross-Connection Control Manual, EPA 570/9-89-007, U.S. Environmental Protection Agency, Office of Water, Washington, DC, June 1989, pp. 17-18.)

In some instances, an air gap cannot be installed and it is necessary to connect a potable water supply to a line, fixture, tank, vat pump, or other equipment to permit backflow of nonpotable water due to backpressure or back siphonage. Under such circumstances, an approved reduced-pressure-principle backflow preventer may be permitted by the regulatory authority. It is essentially a modified double check valve with an atmospheric vent capability placed between the two checks.

Indirect Waste Piping

Waste pipes from fixtures or units in which food or drink is stored, prepared, served, or processed must not connect directly to a sewer or drain. Stoppage in the receiving sewer or drain would permit polluted water to back up into the fixture or unit. Waste piping from refrigerators, iceboxes, food-rinse sinks, cooling or refrigerating coils, laundry washers, extractors, steam tables, egg boilers, steam kettles, coffee urns, dishwashing machines, sterilizers, stills, and similar units should discharge to an open-water-supplied sink or receptacle so that the end of the waste pipe terminates at least 2 inches above the rim of the sink or receptacle, which is directly connected to the drainage system.

A commercial dishwashing machine waste pipe may be connected to the sewer side of a floor drain trap when the floor drain is located next to the dishwashing machine, if permitted by the regulatory agency.

An alternate to the installation of a water-supplied sink waste receptor is the provision of an air gap in the fixture waste line, at least twice the effective diameter of the drain served, located between the fixture and the trap.

The water-supplied sink or air-gap waste receptor should be in an accessible and ventilated space and not in a toilet room.

Plumbing Details

A few typical details and principles are illustrated for convenient reference and as guides to good practice. There are many variations, depending on local conditions and regulations. See Figure 2.15.

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Renewable Energy Eco Friendly

Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable.

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