§ 27-210. General (technical) requirements.

(a)

General. A potable water supply system shall be designed, installed and maintained in such manner as to prevent contamination from nonpotable liquids, solids or gases from being introduced into the potable water supply through cross connections or any other piping connections to the system.

(b)

Cross-connections prohibited. Cross-connections between potable water systems and other systems or equipment containing water or other substances of unknown or questionable safety are prohibited except when and where, as approved by the authority having jurisdiction, suitable protective devices such as the reduced pressure zone backflow preventer or equal are installed, tested and maintained to ensure proper operation on a continuing basis.

(c)

Interconnections. Interconnection between two (2) or more public water supplies shall be permitted only with the approval of the health authority having jurisdiction.

(d)

Individual water supplies. Cross-connections between an individual water supply and a potable public supply shall not be made unless specifically approved by the health authority having jurisdiction.

(e)

Connection to boilers. Potable water connections to boiler feed water systems in which boiler water conditioning chemicals are introduced shall be made through an air gap or provided with an approved backflow preventer located in the potable waterline before the point where such chemicals are introduced.

(f)

Prohibited connections to fixtures and equipment. Connections to the potable water supply system for the following is prohibited unless protected against backflow in accordance with subsection (h) or as set out herein:

(1)

Operating, dissection, embalming, and mortuary tables or similar equipment; in such installation the hose used for water supply shall terminate at least twelve (12) inches away from every point of the table or attachments;

(2)

Pumps for nonpotable water, chemicals or other substances; priming connections may be made only through an airgap;

(3)

Building drainage, sewer or vent systems;

(4)

Any other fixture of similar hazard.

(g)

Refrigerating unit condensers and cooling jackets. Except where potable water provided for a refrigerator condenser or cooling jacket is entirely outside the piping or tank containing a toxic refrigerant, with two (2) separate thicknesses of metal separating the refrigerant from the potable water supply, inlet connection shall be provided with an approved check valve. Also adjacent to and at the outlet side of the check valve, an approved pressure relief valve set to relieve at five (5) psi above the maximum water pressure at the point of installation shall be provided if the refrigeration units contain more than twenty (20) pounds of refrigerants.

(h)

Protection against backflow and backsiphonage.

(1)

Water outlets. A potable water system shall be protected against backflow and backsiphoning by providing and maintaining at each outlet:

a.

Air gap. An air gap as specified in subsection (h)(2) 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; or

b.

Backflow preventer. An approved backflow preventer device or vacuum breaker to prevent the drawing of contamination into the potable water system.

(2)

Minimum required air gap.

a.

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.

b.

Size. The minimum required air gap shall be twice the effective opening of a potable water outlet unless the outlet is a distance less than three (3) times the effective opening away from a wall or similar vertical surface in which cases the minimum required air gap shall be three (3) times the effective opening of the outlet. In no case shall the minimum required air gap be less than shown in the Table I, "Minimum Air Gap for Generally Used Plumbing Fixtures."

Table I—Minimum Air Gaps for Generally
Used Plumbing Fixtures

	Minimum Airgap
Fixture	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 ½″ diameter .....	1.0	1.50
Sink, laundry trays, gooseneck bath faucets and other fixtures with effective openings not greater than ¾″ diameter .....	1.5	2.25
Over rim bath fillers and other fixtures with effective openings not greater than 1″ diameter .....	2.0	3.0
Drinking water fountains—single orifice 7/17 ″ (0.437) diameter or multiple orifices having total area of 0.150 sq. in. (area of circle 7/16 ″ diameter) .....	1.0	1.50
Effective openings greater than 1″	..... (3)	(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 (3) times the diameter of the effective opening for a single wall, or a distance greater than four (4) times the diameter of the effective opening for two (2) intersecting walls.

(2) Vertical walls, ribs or similar obstruction 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 (3) 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 (2) times diameter of effective opening.

(4) Three (3) times diameter of effective opening.

(3)

Approval of devices. Before any device for the prevention of backflow or backsiphonage is installed, it shall have first been certified by a recognized testing laboratory acceptable to the agency director. 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. The agency director or his designee shall inspect routinely such devices and if found to be defective or inoperative shall require the replacement thereof.

(4)

Installation of devices.

a.

Vacuum breakers. Vacuum breakers shall be installed with the critical level at least six (6) inches above the flood level rim of the fixture they serve and on the discharge ode 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 rib but a check valve shall be installed on the discharge side of the vacuum breaker.

b.

Reduced pressure principle backflow preventer. A reduced pressure principle type backflow preventer may be installed subject to full static pressure.

c.

Devices of all types. Backflow and backsiphonage 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 (6) permitted.

(5)

Tanks and vats—Below rim supply.

a.

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 given in Table II, "Sizes of Overflow Pipes for Water Supply Tanks," the overflow pipe shall be provided with an air gap as close to the tank as possible.

Table II—Sizes of Overflow Pipes
for Water Supply Tanks

Maximum Capacity of Water Supply Line to Tank	Diameter of Over- flow Pipe (Inches ID)
0—50 gpm .....	2
50—150 gpm .....	2½
100—200 gpm .....	3
200—400 gpm .....	4
400—700 gpm .....	5
700—1,000 gpm .....	6
Over 1,000 gpm .....	8

 

b.

The potable water outlet to the tank or vat shall terminate a distance not less than one and one-half (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.

c.

The distance from the outlet to the high water level shall be measured from the critical point of the potable water supply outlet.

(6)

Protective devices required. Approved devices to protect against backflow and backsiphonage shall be installed at all fixtures and equipment where backflow and/or backsiphonage may occur and where a minimum air gap cannot be provided between the water outlet to the fixture or equipment and its flood level rim.

a.

Connections not subject to back pressure. Where a water connection is not subject to back pressure, a nonpressure type vacuum breaker shall be installed in 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 Table III, "Cross-Connections Where Protective Devices are Required and Critical Level (C-L) Settings for Backflow Preventers."

Table III—Cross-Connections Where Protective Devices Are Required and Critical Level (C-L) Settings for Backflow Preventers

Fixture or Equipment	Method of Installation
Aspirators and ejectors	C-L at least 6 in. above flood level of receptacle served.
Dental units .....	On models without built-in vacuum breakers—C-L at least 6 in. above flood level rim of bowl.
Dishwashing machines .....	C-L at least 6 in. above flood level of machine. Install on both hot and cold water supply lines.
Flush tanks .....	Equip with approved hall cock. Where ball cocks touch tank water equip with vacuum breaker at least 1 in. above overflow outlets. Where ball cock does not touch tank water install ball cock outlet or provide vacuum breaker as specified above.
Flushometers (closet & urinal) .....	C-L at least 6 in. above top of fixture supplies.
Garbage can cleaning machine .....	C-L at least 6 in. above flood level of machine. Install on both hot and cold water supply lines.
Hose bibbs (where aspirators or ejectors could be connected.) .....	C-L at least 6 in. above flood level of receptacle served.
Hose outlets .....	C-L at least 6 in. above highest point on hose line.
Laundry machines .....	C-L at least 6 in. above flood level of machine. Install on both hot and cold water supply lines.
Lawn sprinklers .....	C-L at least 12 in. above highest sprinkler or discharge outlet.
Steam tables .....	C-L at least 6 in. above flood level.
Tank and vats .....	C-L at least 6 in. above flood level rim or line.
Trough urinals .....	C-L at least 30 in. above perforated flush pipe.

 

b.

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 backsiphonage where the water connection is subject to back pressure, and an air gap cannot be installed, the director may require the use of an approved reduced pressure principle backflow preventer. A partial list of such connections is shown in Table IV, "Partial List of Cross-Connections Subject to Back Pressure."

Table IV-Partial List of Cross-Connections Which May Be Subject to Back Pressure

Chemical lines

Dock water outlets

Hose bibbs

Individual water supplies

Industrial process water lines

Pressure tanks

Pumps

Steam lines

Swimming pools

Tank and vats—Bottom inlets

(7)

Barometric loop. Water connections where an actual or potential backsiphonage hazard exists may in lieu of devices specified in subsection (h)(6) be provided with a barometric loop. Barometric loops shall precede the point of connection.

(8)

Double check-double gate valves. The director may authorize installation of approved, double check-double gate valve assemblies with test cocks as protective devices against backflow in connections between a potable water system and other fluid systems which present no significant health hazard in the judgment of the director.

(9)

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 ten (10) psi or less 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 the other outlets.

(Code 1961, § 17-113; Ord. No. 17175, § 3, 2-18-87)