SS 7 covers automatic backflow preventers connected to a drinking-water supply, such as reduced pressure zone devices and double check valves, which stop contaminated water flowing back into the supply. They are typically tested annually by an IQP, often to AS/NZS 2845.3, and certified on Form 12A.
At a glance
| Specified system | SS 7 |
| Official name | Automatic back-flow preventers connected to a potable water supply |
| Typical intervals | Annual (varies by task; see below) |
| Standards often cited | AS/NZS 2845.1, AS/NZS 2845.3, AS/NZS 3500.1 |
| Annual certificate | Form 12A from an IQP, attached to the building warrant of fitness |
What SS 7 covers
- Listed where the device connects to a potable supply and sits wholly within the property boundary, or partly within it and is not owned by the network utility operator.[1]
- Handbook examples: reduced pressure zone devices, double check valve assemblies, pressure type vacuum breakers, atmospheric vacuum breakers.[1]
- Marlborough's form also lists hose connection vacuum breakers.[2]
- G12/AS1 requires backflow protection wherever contaminants could flow back into the potable system; protection is an air gap or a backflow prevention device selected by hazard.[3]
- G12/AS1 hazard levels: high (potential to cause death), medium (potential to injure or endanger health), low (nuisance by colour, odour or taste).[3]
- G12/AS1 Table 2A: high-hazard premises need an air gap or RPZ device; medium-hazard an air gap or double check valve assembly.[3]
Which buildings have it
- Ashburton DC policy examples of high-risk premises: hospitals, laboratories, chemical plants, commercial dishwashers (RPZ listed).[4]
- Ashburton DC examples of medium-risk: commercial laundries, garden irrigation, carbonated drink dispensers, pools (testable DCV listed).[4]
How often it is inspected
| System | Daily | Weekly | Monthly | 3-monthly | 6-monthly | Annual | 2–5 yr |
|---|---|---|---|---|---|---|---|
| SS 7 Backflow preventers | no | no | no | no | no | no |
| Task | Typical frequency | Who |
|---|---|---|
| Test atmospheric vacuum breakers (poppet/float closes on pressure rise, opens on fall) | Annually | —[1] |
| Inspect non-testable automatic preventers; repair or replace if leaking/faulty | Annually | —[1] |
| Inspect and test any preventer | After repair or replacement | —[1] |
| Inspection/testing to nominated standard | Annually | IQP[5] |
| Form 12A certificate | Annually | IQP[5] |
| Keep records (dates, work, faults, remedies, who) in on-site logbook or electronically | Previous 24 months | Owner[5] |
| Annual testing follows the SS 7 compliance schedule (except devices in single residential dwellings) | Annually | —[3] |
What an inspection typically covers
- Regular testing plus planned preventative and responsive maintenance so the device protects the drinking water supply.[5]
- Devices must be testable in service; isolating valves fitted either side of RPZ, DCV and PVB devices.[3]
- Testing after installation or repair, to AS/NZS 2845.3 or the NZ backflow testing standard.[3]
- Invercargill 2018 SS 7 form asks for technical data sheets for each device to be attached.[7]
Local water supplier rules
Some councils add their own backflow testing rules. One example:
- Ashburton DC: devices tested on or before each 12-month anniversary to AS/NZS 2845.3 by a Council-approved IQP; results sent to Council electronically; Council may require more frequent tests.[4]
- Ashburton DC: Building Act devices must be included in the BWOF; non-residential consents need a backflow risk assessment tied to the SS compliance schedule.[4]
- Invercargill, PNCC and Marlborough SS 7 forms state no separate water-supplier notification requirement.[5]
Standards commonly cited
| Standard | Title |
|---|---|
| AS/NZS 2845.1:2022 | Water supply - Backflow prevention devices, Part 1: Materials, design and performance requirements[6] |
| AS/NZS 2845.3:2020 (Section 2) | Water supply - Backflow prevention devices - Part 3: Field testing and maintenance of testable devices[8] |
| NZ Backflow Testing Standard (2019; earlier 2011) | Field testing of backflow prevention devices and verification of air gaps (Master Plumbers / Water NZ)[2] |
| US EPA Cross-Connection Control Manual (2009) | Cross-Connection Control Manual[5] |
| AS/NZS 3500.1 (2021, 2018) | Plumbing and drainage, Part 1: Water services[2] |
Titles as listed in council and MBIE documents. Inspections follow the standard and edition named in the building's compliance schedule, usually the edition the system was installed to. Changing to a different edition needs an amendment to the compliance schedule.
Building Code context
- NZBC G12.3.2: potable supply protected from contamination, including within the system and the water main.[3]
- Acceptable Solution G12/AS1 (Amendment 14, effective 2 Nov 2024) sections 3.3-3.8 cover backflow hazards, devices and testing.[3]
Questions
How often is SS 7 inspected?
MBIE and council guidance shows tasks at these intervals: annual, with an IQP certifying the system each year. The building's compliance schedule sets the actual frequency.
Which standards apply to SS 7?
Commonly cited: AS/NZS 2845.1, AS/NZS 2845.3, AS/NZS 3500.1. The compliance schedule names the standard and edition for each building.
Who can certify SS 7?
An independently qualified person (IQP) registered with the council for this system. They issue a Form 12A each year, which the owner attaches to the building warrant of fitness.
Sources
- Compliance Schedule Handbook, Amendment 3 — MBIE, 14 February 2014 (first published 25 May 2007)
- SS 07 Automatic Backflow Preventers template — Marlborough District Council
- Acceptable Solutions and Verification Methods for Clause G12 Water Supplies, 3rd ed, Amendment 14 — MBIE, 2024-11-02
- Backflow Prevention Policy 2021 — Ashburton District Council, 2021-07-28
- SS7 Automatic Backflow Prevention Devices (v3) — Invercargill City Council, 2024-08-20
- Specified Systems Guidance for Customers, WBCA 003 v1.0.1 — Westland District Council BCA, 16 September 2025
- SBCG SS 7 Automatic Backflow Preventers — Invercargill City Council (Southland Building Control Group), 2018-01
- AS/NZS 2845.3:2020 entry — MBIE Codehub, valid from 2020-02-13
General information only, not legal or engineering advice. Last reviewed 30 October 2026. Spotted something out of date? Let us know.
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