(A) Water outlets. A potable water system shall be protected against backflow and back-siphonage by providing and maintaining at each outlet:
(1) Air gap. An air gap, as specified in division (B) of this section, between the potable water outlet and the flood-level rim of the fixture it supplies or between the outlet and any other source of contamination.
(2) Backflow preventer. An approved device or means to prevent backflow.
(B) Minimum required air gap.
(1) How measured. The minimum required air gap shall be measured vertically from the lowest end of a potable water outlet to the flood rim or line of the fixture or receptacle into which it discharges.
(2) Size. The minimum required air gap shall be twice the effective opening of the potable water outlet unless the outlet is a distance less than three times the effective opening away from a wall or similar vertical surface, in which cases the minimum required air gap shall be three times the effective opening of the outlet. In no case shall the minimum required air gap be less than shown in Table A.
(C) Approval of devices.
(1) Before any device for the prevention of backflow or back-siphonage is installed, it shall have first been certified by a recognized testing laboratory acceptable to the agency. Devices installed in a building potable water supply distribution system for protection against backflow shall be maintained in good working condition by the person or persons responsible for the maintenance of the system.
(2) The agency or his designee shall inspect routinely these devices and if they are found to be defective or inoperative, shall require the replacement thereof.
(D) Installation of devices.
(1) Nonpressure type vacuum breakers. Atmospheric vacuum breakers shall be installed with the critical level at least six inches above the flood-level rim of the fixture they serve and on the discharge side of the last control valve to the fixture. No shutoff valve or faucet shall be installed beyond the vacuum breaker. For closed equipment or vessels such as pressure sterilizers the top of the vessel shall be treated as the flood-level rim but a check valve shall be installed on the discharge side of the vacuum breaker.
(2) Reduced pressure principal backflow preventer. A reduced pressure principal type backflow preventer may be installed subject to full static pressure.
(3) Devices of all types. Backflow and back-siphonage preventing devices shall be accessibly located, preferably in the same room with the fixture they serve. Installation in utility or service spaces, provided they are readily accessible, is also permitted.
(E) Tanks and vats; below rim supply.
(1) Where a potable water outlet terminates below the rim of a tank or vat and the tank or vat has an overflow of diameter not less than that given in Table B, the overflow pipe shall be provided with an air gap as close to the tank as possible.
(2) The potable water outlet to the tank or vat shall terminate a distance not less than 1½ times the height to which water can rise in the tank above the top of the overflow. This level shall be established at the maximum flow rate of the supply to the tank or vat and with all outlets except the air gap overflow outlet closed. The distance from the outlet to the high water level shall be measured from the critical point of the potable water supply outlet. The Figure A illustrates this principal.
(F) Protective devices required. Approved devices to protect against backflow and back-siphonage shall be installed at all fixtures and equipment where backflow and/or back-siphonage may occur and where minimum air gap cannot be provided between the water outlet to the fixture or equipment and its flood- level rim.
(1) Connections not subject to back pressure. Where a water connection is not subject to back pressure, a vacuum breaker shall be installed on the discharge side of the last valve on the line serving the fixture or equipment. A list of some conditions requiring protective devices of this kind is given in the Table 3.86A of Ord. 553 hereby adopted by reference.
(2) Connections subject to back pressure. Where a potable water connection is made to a line, fixture, tank, vat, pump or other equipment with a hazard of backflow or back-siphonage where the water connection is subject to back pressure, and an air gap cannot be installed, the City Administrator will require adequate protection which may include the use of an approved reduced pressure principle backflow preventer. A partial list of such connections is shown on Table 3.86B of Ord. 553 hereby adopted by reference.
(G) Low pressure cutoff required on booster pumps. When a booster pump is used on a water pressure booster system and the possibility exists that a positive pressure of less than 20 psi may occur on the suction side of the pump, there shall be installed a low pressure cutoff on the booster pump to prevent the creation of a vacuum or negative pressure on the suction side of the pump, thus cutting off water to other outlets.
(Ord. 553, passed 5-1-89) Penalty, see § 50.99
Table A: Minimum Air Gaps for Generally Used Plumbing Fixtures | ||
Fixture | Minimum Air Gap | |
When Not Affected by Near Wall 1 (Inches) | When Affected by Near Wall 2 (Inches) | |
Table A: Minimum Air Gaps for Generally Used Plumbing Fixtures | ||
Fixture | Minimum Air Gap | |
When Not Affected by Near Wall 1 (Inches) | When Affected by Near Wall 2 (Inches) | |
Lavatories and other fixtures with effective openings not greater than 1/2-inch diameter | 1.0 | 1.50 |
Sink, laundry trays, goose-neck bath faucets and other fixtures with effective openings not greater than 3/4-inch diameter | 1.5 | 2.25 |
Over rim bath fillers and other fixtures with effective openings not greater than 1-inch diameter | 2.0 | 3.0 |
Drinking water fountains-single orifice 7/16 (0.437)-inch diameter or multiple orifices having total area of 0.150 square inch (area of circle 7/16- inch diameter) | 1.0 | 1.50 |
Effective openings greater than 1 inch | See note 3 | See note 4 |
1 Side walls, ribs, or similar obstructions do not affect air gaps when spaced from inside edge of spout opening a distance greater than three times the diameter of the effective opening for a single wall, or a distance greater than four times the diameter of the effective opening for two intersecting walls. | ||
2 Vertical walls, ribs, or similar obstructions extending from the water surface to or above the horizontal plane of the spout opening require a greater air gap when spaced closer to the nearest inside edge of spout opening than specified in note 1 above. The effect of three or more such vertical walls or ribs has not been determined. In such cases, the air gap shall be measured from the top of the wall. | ||
3 Two times diameter of effective opening. | ||
4 Three times diameter of effective opening. | ||
Table B: Sizes of Overflow Pipes for Water Supply Tanks
| |||
Maximum Capacity of Water Supply Line to Tank
|
Diameter of Overflow Pipe (Inches ID) | Maximum Capacity of Water Supply Line to Tank
|
Diameter of Overflow Pipe (Inches ID) |
0 - 50 gpm | 2 | 400 - 700 gpm | 5 |
50 - 150 gpm | 2½ | 700 - 1,000 gpm | 6 |
100 - 200 gpm | 3 | Over 1,000 gpm | 8 |
200 - 400 gpm | 4 | ||
Figure A: Properly Protected Tank below Rim Supply
