What is the primary purpose of an RPZ backflow preventer?

To protect potable water supplies from contamination in high-hazard cross-connections where back-siphonage or back-pressure could introduce harmful substances. (Clause 1)

How does an RPZ device work?

It uses two independently acting check valves with an intermediate reduced pressure zone and a differential pressure relief valve. If a pressure drop occurs, the relief valve opens to discharge water, creating an air gap and preventing backflow. (Clause 5.1)

At what pressure differential does the relief valve open?

The relief valve must open and discharge to atmosphere when the pressure in the intermediate zone drops to 14 kPa or less above atmospheric pressure. (Clause 6.2)

Does this standard cover installation procedures?

No, this standard is a product specification for the device itself. Installation requirements are covered by plumbing codes like the National Building Code (NBC) of India.

IS 14948 Part 1

: 2001

Backflow Prevention Devices - Air Gaps for Water Supply Installations

CurrentSpecializedSpecificationBIMMEP · Plumbing Fixtures and Valves

Download PDF BIS Portal Google

This standard specifies the requirements for Reduced Pressure Zone (RPZ) backflow prevention devices. It details the materials, design, construction, performance criteria, and testing methods to ensure these devices effectively protect potable water systems from contamination in high-hazard applications.

Specifies requirements for air gaps as a means of backflow prevention in water supply installations.

Quick Reference Values

Relief valve opening pressure differentialMust open when zone pressure is 14 kPa (or less) above atmospheric pressure

First check valve pressure requirementMust be drip-tight in the direction of flow when the inlet pressure is 3.5 kPa or greater

Hydrostatic test pressureDevice body must withstand 2 times the maximum working pressure for 15 minutes without leakage

Maximum rated working pressure1.2 MPa

Maximum water temperature45 °C

Key Formulas

g ≥ 2 * di — Minimum air gap 'g' for a circular inlet of diameter 'di'

g ≥ 20 mm — Absolute minimum allowable air gap

Practical Notes

RPZ devices must be installed in locations with adequate drainage as they are designed to discharge water from the relief port during backflow events.

Annual testing and certification by a qualified professional are critical to ensure the device remains functional and compliant.

Installation must be done according to manufacturer's instructions and local plumbing codes, paying close attention to required orientation (usually horizontal) and clearances for testing and maintenance.