Backflow Prevention and Cross-Control Program

Backflow Prevention Guide

BACKFLOW

Backsiphonage

Backsiphonage can be described as “a reversal of the normal direction of flow in a piping system due to a drop in the supply pressure to the point where a vacuum, partial vacuum or negative pressure occurs in the upstream piping”.

Causation

Backsiphonage can be caused in the water user’s system by insufficient internal piping hydraulic capacity, by a drop in pressure in the user’s upstream piping, or by a drop in pressure in the public water system. Generally, backsiphonage occurs more frequently in the water user’s system inside the building and on the upper floors, than to the public water system since the volume or duration of a backsiphonage condition is usually not of sufficient quantity or duration to reach the public water system.

Backsiphonage can be caused:

• In the public water system by a water main break
• By a break in the consumer’s piping
• If the water is turned off for maintenance or repair
• If a fire hydrant is struck
• If the fire department is drawing water to fight a fire
• By any abnormally heavy water use from the water main

Backpressure

Backpressure can be described as “a reversal of the normal direction of flow in a piping system due to a downstream pressure that is greater than the normal supply pressure”. When the pressure is greater in a water user’s water system than the pressure in the public water system, then the water will reverse its normal direction of flow and move towards the public water system.

Causation

Backpressure can be created by:

• Boilers
• Chillers
• Internal pumping systems
• Any other system that can create a water pressure that is greater than the normal supply pressure

Pumps

So if a fixture, such as a boiler, creates a pressure greater than the supply pressure then there will be backflow unless the appropriate backflow prevention device is installed. Pumps on secondary or auxiliary water system installations are a primary cause of backpressure and can be found at a variety of premises.

A typical backflow situation involving pumps is illustrated by visualizing a pump supplying well water to a plumbing system that is also connected to the public water supply. If the pump is capable of producing a higher pressure than the public water system or if the public water system pressure should drop, then the pump can discharge its water through the internal plumbing system into the public water main.

Cross-Connection

Suspect  Cross-Connections?  Please report that information to Village Hall or email LGambosi@middlefieldohio.com 

A cross-connection can be described as “any arrangement whereby backflow can occur”, or as “any arrangement of pipes, fittings, fixtures, or devices that connects a non-potable water system to a potable water system”. It is the point at which a water-using fixture is connected to the water user’s potable water system.

An Unprotected Cross-Connection

An unprotected cross-connection provides the path or route through which backflow can occur, and it can be:

• Actual or potential
• Direct (subject to backpressure and backsiphonage) such as a boiler or indirect (subject to backsiphonage only) such as a toilet tank fill valve
• Permanent or temporary

Common Examples

• Boiler make-up lines
• Chiller make-up lines
• Commercial grade dishwashers
• Commercial grade garbage disposals or grinders
• Fire protection systems
• Hand-held lawn sprayers
• Hose bibs with a hose attached
• Irrigation systems
• A janitor’s sink with a hose attached
• Pressure washers
• Soap, sanitizer or wax induction systems
• Spray hoses
• Suction tees or aspirators
• Tanks or vats with a submerged inlet
• Toilet tanks
• Urinals
• X-rays and photo developing equipment