Backflow and Water System Safety Notes

Hazard Levels (Ohio Department of Commerce Terminology)

  • Low Hazard (Pollution Hazard): Aesthetically objectionable but not harmful. E.g., funny smell or taste.
  • High Hazard (System Hazard): May damage the system or harm the user. E.g., chemical additives in fire suppression or boiler systems (propylene glycol).
  • Severe High Hazard: Threat of death. Requires an air gap. E.g., systems containing ethylene glycol (antifreeze).
    • Ethylene glycol is extremely toxic; a teaspoon can be fatal.
  • Chemical additives generally indicate a high hazard, while ethylene glycol specifically indicates a severe high hazard.

Absolute Pressure

  • Absolute Pressure: Gauge pressure plus atmospheric pressure.
  • Measured in pounds per square inch absolute (PSIA).
  • Atmospheric Pressure: Pressure exerted by the atmosphere's weight (14.7 PSIG at sea level).
    • Decreases with increasing altitude.
    • Use 14.7 for calculations, even if above sea level.
  • Impact on golf: Higher atmospheric pressure in Florida reduces ball distance compared to locations with lower pressure.

Air Gap

  • Air Gap: Unobstructed vertical distance through free atmosphere between water supply outlet and flood level rim of a fixture.
  • Common backflow prevention method.
  • Examples: Bathroom faucets, bathtubs, drinking fountains.
  • Approved Air Gap Separation: Two times the nominal diameter of the supply pipe discharge opening, but never less than one inch.
  • Importance: Prevents back siphonage due to atmospheric pressure.
  • Increased Separation: May be required (three times diameter) near corners or walls (page 27).

Atmospheric Vacuum Breaker

  • Atmospheric Vacuum Breaker: Mechanical device with float check valve and air inlet port to prevent back siphonage.
  • Prevents back-siphonage.
    • Common uses: mop sink faucets, shampoo bowls, commercial dishwashers.

Auxiliary Water System

  • Auxiliary Water System: Any water system besides the public water system (e.g., well, cistern).
  • Allowed in commercial situations only (not residential).
  • Requires specific valves to prevent cross-connection between auxiliary and city water (pages 53-54).
  • In residential settings, a well for farming purposes alongside city water requires a secondary containment device (RPD).

Backflow

  • Backflow: Unintentional reversal of normal flow, potentially causing pollution or contamination.
  • Pollution: Low hazard.
  • Contamination: High hazard.
  • Two Types:
    • Backpressure Backflow: Downstream pressure exceeds supply pressure. E.g., boiler system with higher pressure.
      • Requires backflow preventer.
    • Back Siphonage: Caused by negative pressure or drop in supply pressure.
      • Atmospheric pressure (14.7 psi) can push water up to 34 feet.
      • Negative pressure created by a water main break can cause back siphonage.
      • Example: Draining a hot tub using a garden hose.
      • Install containment device to prevent backflow.

Bypass

  • Bypass: Arrangement to divert flow around a backflow preventer.
  • Must have the same level of protection as the main system.
  • Common in hospitals to ensure continuous water supply during testing or maintenance.
  • Does not need to be the same size pipe.

Containment Principle Backflow Prevention Device

  • Containment Principle Backflow Prevention Device: Prevents polluted or contaminated water from entering the public water system.
  • Located at the outlet side of the meter or service entrance.
  • Purpose: Protects the public water supply.
  • Falls under EPA guidelines.

Contaminant vs Contamination

  • Contaminant: Liquid, solid, or gas posing a health threat.
  • Contamination: Introduction of a contaminant into the water system (high hazard).

Continuous Pressure

  • Continuous Pressure: Water pressure supplied to a device for more than 12 hours.
  • Continuous: >12 hours, can be left on.
  • Non-Continuous: <12 hours, must be turned off.
  • Certain devices (e.g., atmospheric vacuum breaker) cannot have continuous pressure.

Critical Installation Level

  • Critical Installation Level: Specific height requirement for certain backflow devices.
  • Atmospheric Vacuum Breaker (1001): 6 inches.
  • Pressure Vacuum Breaker (1020): 12 inches.
  • Ensures proper backflow prevention.
  • Each device has different requirements.

Cross Connections

  • Cross Connection: Arrangement connecting a non-potable system to a potable system, allowing backflow.
    Examples: Garden hose in a bucket, mop sink faucet with hose.
    Cross Connection Control: Method to prevent backflow through a cross connection. Using a fill volume that's ASSE rated.

Degree of Hazard

  • Degree of Hazard: Classification of potential harm.
    • Low Hazard: Pollution (smells/tastes funny).
    • High Hazard: Contamination (toxic).
    • Severe High Hazard: Ethylene Glycol(air gap).
    • Low hazard is a pollution and is nontoxic, so high hazard is toxic.
  • Choosing Devices: When selecting a backflow device, consider whether it's suitable for backpressure, back siphonage, continuous pressure, and the hazard level.

Definitions

  • Indirect connection.
  • Pressure is indicated as pounds per square. Differential PSID.
  • Differential Pressure Gauge: Measures pressure difference across a check valve.
  • Hoses: Red for high, blue for low, green/yellow for vent.

Double Check Valve Assembly

  • Double Check Valve Assembly: Backflow prevention device with two spring-loaded check valves.
    **Four Test Cocks: Test cock 1 is always placed before shut of valve number one.
    *Test cocks are appropriately located.
  • Springs are parts that are interchangeable.
  • Detect meter measures all rates of flow.

Ethylene Glycol

  • Subatance added to water to decreases the temperature at which the water will freeze.
  • Presents a severe high hazard requiring an air gap.
    Is the maximum height that fluid can reach in a vessel.

Isolation Principle Device

**Installed at supply line to fixture and is designed to prevent backflow into water system.

  • Always has isolation device.
    *Is the responsibility of higher department.
    *Negative pressure is created when there is pressure below prevailing atmospheric pressure.
    Non potable substance that is unsafe for human consumption.
    *Pressure vacuum breaker has a closing inlet and outlet valves.

Propylene Glycol

  • Similar glycol except it is food.
    *It used to be used in fire suppression till 2022.

Reduces pressure principle backflow printer.

*There has to be two pounds less than supply pressure to be effective.

  • There is a certain pressure one has to obtain when using this particular backflow.

Refusal Of Service.

  • If a customer refuses to repaisomething in the infrastructure that is broken or failing. The water company has right to refuse service.

Solar Water Systems

*Chemically treated systems need a reduce pressure principle valve.

Thermal Expansion

  • Thermal Expansion: Water volume increases when heated, creating a closed system with backflow preventers.
  • Requires a Thermal Expansion Tank: To accommodate increased volume, preventing pressure buildup.
  • Tank Lifespan: 4-5 years.
  • Installation: Must be strapped, not pipe-supported.
  • Local codes may require thermal expansion tanks in certain situations.

Venturi Principle

  • Venturing Principle: Fluid velocity increases and pressure decreases when flowing through a constriction, creating a vacuum.
  • Applications: Water-activated sump pumps, commercial car washes.
    Used in power washers.

Upstream and Downstream

*Important points to consider include, before and after.
*The relationship the water has these points.

Water Submerge and air gaps.

*Water cannot be 35 feet above flood line
*When pumps break it can cavitate that water main. Putting a cutoff switch can mitigate this.

  • Test is done by turning off the water pressure for the line.

Plumbing and Code Laws.

*The state needs to adopt these requirements, some states differ in their approach.
*There as some chemicals and substances that should not cause toxic coditious in the water.
*It can not be introduced and utilized in substance.
*The test one is always upstream to shutoff valve number one. It’s high hazard.
*Signage needs to be used when something is potable or use purple in color if nonpotable.
*Use a good piping system and has pressure, its gotta go someplace.
*Do not put tubing in a carbine area or this can create carbon sulfide. The use should be ten twenty.
There are other ways to make a hot box. Do not set up temporary equipment.