SAWS: Backflow Prevention Devices
Aquifer Beaker

Edwards Aquifer

Aquifer Level 657.8'
9/19/17 - Official

The Edwards aquifer and its catchment area in the San Antonio region is about 8,000 square miles and includes all or part of 13 counties in south-central Texas.

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Landscape Watering
Last Digit of Address Watering Day
0 or 1 Monday
2 or 3 Tuesday
4 or 5 Wednesday
6 or 7 Thursday
8 or 9 Friday
No Watering on Weekends

Stage 1:
Water once a week

Watering with an irrigation system or sprinkler is allowed only once a week before 11 a.m. or after 7 p.m. on your designated watering day as determined by your address.

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Aquifer Level 657.8 | Stage 1: Water once a week

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Backflow Prevention Devices

Air Gap drawing

An air gap is a vertical, physical separation between the end of a water supply outlet and the flood-level rim of a receiving vessel. This separation must be at least twice the diameter of the water supply outlet and never less than 1 inch.

An air gap is effective against backpressure backflow and back-siphonage and may be used to isolate health or non-health hazards.

RPBA drawing

A Reduced-pressure Principle Backflow Assembly (RPBA) includes two independently acting, spring-loaded check valves with a hydraulically operating, mechanically independent, spring-loaded pressure differential relief valve in between. Testing is required for this type of BPA. An RPBA is effective against backpressure backflow and back-siphonage and may be used to isolate health or non-health hazards.

PVB drawing

A Pressure Vacuum Breaker (PVB) consists of an independently acting, spring-loaded check valve and an independently acting, spring-loaded, air inlet valve. This assembly requires testing. A PVB may be used to isolate health or non-health hazards but is effective against back-siphonage only.

DCVA drawing

A Double Check Valve Assembly (DCVA) consists of two independently acting, spring-loaded check valves. This type of assembly requires testing. A DCVA is effective against backpressure backflow and back-siphonage but should be used only to isolate non-health hazards.