Principles of Backflow practice

All 13 free principles of backflow questions

1. Backflow in a water system can be caused by:

   • A Backpressure only Backpressure is one cause, but the definition names back siphonage as a second one.
   • B Backsiphonage only Backsiphonage is one cause, but the definition names backpressure as well.
   • C Both backpressure and backsiphonage Correct
   • D Constant high pressure in the mainline Steady pressure in the mainline is normal operation and is not named as a cause of reversed flow.

   Either condition can carry irrigation water back into the potable supply, because Texas Commission on Environmental Quality (TCEQ) rules define backflow prevention as stopping a reversal of flow caused by back siphonage or by backpressure (30 TAC 344.1(3)).

   30 TAC 344.1(3)

2. Which backflow device does TCEQ NOT allow on a new irrigation system?

   • A A pressure vacuum breaker The pressure vacuum breaker is still on the list of allowed methods where there is no backpressure.
   • B A spill-resistant vacuum breaker The spill-resistant vacuum breaker is the device the 2020 amendment added in place of the atmospheric one.
   • C A reduced pressure assembly The reduced pressure principle assembly remains an allowed method, including at a health hazard.
   • D An atmospheric vacuum breaker Correct

   The Texas Commission on Environmental Quality (TCEQ) amended its landscape irrigation rule effective July 26, 2020 to replace the atmospheric vacuum breaker (AVB) with the spill-resistant vacuum breaker, because an AVB will not work correctly with a valve downstream. Since that date the AVB is no longer an allowed method on a new system (30 TAC 344.50(b)(4)).

   30 TAC 344.50(b)(4); TCEQ, Quick Reference Guide to All Changes to 30 TAC Chapter 344 (2020), p. 18 Includes a reference document, not law.

3. Which backflow device may be set below ground?

   • A A reduced pressure assembly A reduced pressure principle assembly must be installed at least 12 inches above ground where it cannot be submerged.
   • B A pressure vacuum breaker A pressure vacuum breaker must be at least 12 inches above all downstream piping and the highest downstream opening.
   • C A double check assembly Correct
   • D A spill-resistant vacuum breaker A spill-resistant vacuum breaker carries the same 12 inch height rule as the pressure vacuum breaker.

   The rule sets below-ground installation requirements only for double check valve assemblies (30 TAC 344.50(d)). The reduced pressure assembly must sit at least 12 inches above ground, and the vacuum breakers at least 12 inches above the highest downstream opening. A city may still bar the double check locally.

   30 TAC 344.50(d)

4. An air gap must be at least twice the outlet diameter and never less than:

   • A 1 in Correct
   • B 2 in The floor is 1 inch; a 2 inch gap is only the minimum for a 1 inch outlet.
   • C 6 in Six inches was the old atmospheric vacuum breaker height, not the air gap floor.
   • D 12 in Twelve inches is a vacuum breaker and reduced pressure assembly height, not the air gap floor.

   The vertical separation of an air gap must be at least twice the diameter of the supply outlet, and it may never be less than 1.0 inch whatever size the outlet is (30 TAC 344.1(1)).

   30 TAC 344.1(1)

5. On a system designated a health hazard, the backflow assembly must be tested:

   • A Only when installed A test on installation alone is the minimum for a non-health hazard system; a health hazard system adds a yearly test.
   • B Once every three years Three years is the term of an irrigator license, not the testing interval.
   • C At least once a year Correct
   • D Only after a repair A test follows any repair, but a health hazard assembly must also be tested every year.

   Assemblies on irrigation systems designated as health hazards must be tested annually, on top of the test every assembly gets on installation, repair, replacement or relocation (30 TAC 344.50(e)).

   30 TAC 344.50(e)

6. What causes backsiphonage?

   • A A booster pump on the system A pump raises downstream pressure, which is listed as a cause of backpressure.
   • B Heads set above the backflow device Raised piping and heads add elevation pressure downstream, which is a cause of backpressure.
   • C A vacuum in the water supply line Correct
   • D Downstream pressure above supply pressure Downstream pressure above the supply is the definition of backpressure.

   Backsiphonage is backflow caused by supply pressure dropping below atmospheric pressure, because the vacuum in the supply line then pulls water back from the irrigation side. Pumps, raised heads and higher downstream pressure push water back instead, and that is backpressure.

   RG-478, p. 5 Reference document, not law.

7. What condition creates backpressure?

   • A Downstream pressure above supply pressure Correct
   • B Supply pressure dropping below atmospheric Supply pressure falling below atmospheric is the definition of backsiphonage.
   • C Heavy use at a nearby fire hydrant Heavy hydrant use lowers pressure in the mains, which causes backsiphonage.
   • D An undersized water meter An undersized meter causes pressure loss on the way in; it does not raise pressure downstream above the supply.

   Backpressure requires downstream pressure that overcomes the supply pressure and pushes water back toward the source. A drop in supply pressure, such as heavy hydrant use, pulls water back instead, and that is backsiphonage.

   RG-478, p. 7 Reference document, not law.

8. What must a public water system be physically linked to for a cross-connection to exist?

   • A A fire hydrant on the same main A fire hydrant is part of the public water system, not another source of water.
   • B A second meter on the same service A second meter still carries potable water from the same system.
   • C A water source of questionable quality Correct
   • D A pressure regulator at the house A pressure regulator carries the same potable water and adds no other source.

   A cross-connection exists only where a public water system is linked to a supply of unknown or questionable quality, a source that may contain contaminants, or water treated to a lesser degree (30 TAC 344.1(7)). Hydrants, meters and regulators are parts of the potable system itself and bring in no other source.

   30 TAC 344.1(7)

9. A PVB must be installed at least:

   • A 12 in above the highest downstream head Correct
   • B 6 in above the highest downstream sprinkler Six inches above the outlets was the atmospheric vacuum breaker's height, not the pressure vacuum breaker's.
   • C 12 in above the ground Twelve inches above ground is the reduced pressure principle assembly's rule; the pressure vacuum breaker is measured from the highest head.
   • D Below grade in a valve box Only the double check may be installed below ground.

   A pressure vacuum breaker (PVB) must sit at least 12 inches above all downstream piping and the highest downstream opening (30 TAC 344.50(b)(3)(B)). Its height is measured against the heads it serves, not against the ground.

   30 TAC 344.50(b)(3)(B)

10. How high above ground must an RP be installed?

    • A At least 6 in Six inches was the old atmospheric vacuum breaker height; the reduced pressure assembly needs 12 inches.
    • B At least 12 in Correct
    • C At least 18 in The minimum is 12 inches above ground, not 18.
    • D At least 24 in The minimum is 12 inches above ground, not 24.

    A reduced pressure principle assembly (RP) must be installed at least 12 inches above ground in a place where it cannot be submerged, and drainage must be provided for water its relief valve discharges (30 TAC 344.50(b)(2)).

    30 TAC 344.50(b)(2)(A)

11. Water that is suitable for people to drink is called:

    • A Reclaimed water Reclaimed water is treated wastewater and is listed as a non-potable source.
    • B Non-potable water Non-potable water is defined as water not suitable for human consumption.
    • C Graywater Graywater is household wastewater and is listed as a non-potable source.
    • D Potable water Correct

    Potable water means water suitable for human consumption that meets the definition of drinking water (30 TAC 344.1(37)). Reclaimed water and graywater are both listed as non-potable sources and are not fit to drink.

    30 TAC 344.1(37)

12. An RP on a new system has just been tested. Within what time must the results reach the local water purveyor?

    • A 5 business days The rule allows ten business days, not five.
    • B 10 business days Correct
    • C 10 calendar days The period is counted in business days, not calendar days.
    • D 30 calendar days The rule allows ten business days, well short of thirty calendar days.

    The irrigator must make sure the assembly is tested before the system goes into service and that the results reach the local water purveyor within ten business days of the test (30 TAC 344.52(c)).

    30 TAC 344.52(c)

13. Heads and piping set well above the backflow device can cause backflow by:

    • A Backpressure Correct
    • B Backsiphonage Backsiphonage comes from a drop in supply pressure that pulls water back; raised piping pushes water back from downstream.
    • C Water hammer Water hammer is a pressure surge when flow stops suddenly, not the steady push from piping set above the device.
    • D Thermal expansion Thermal expansion comes from heated water; raised heads and piping add pressure by their height, not by heat.

    Backpressure is any rise in downstream pressure above the supply pressure, and the Texas Commission on Environmental Quality (TCEQ) guide RG-478 names elevation of piping as one cause alongside a pump. Heads and piping set high above the device therefore push water back toward the supply rather than pulling it.

    RG-478, p. 6 Reference document, not law.