Gas Excess Flow Valves (EFVs) Explained — AS/NZS 5601.1 Cl 5.2.11 (2026 Guide)
Summary (TL;DR)
AS/NZS 5601.1:2022 (Clause 5.2.11) now requires fire emergency isolation wherever multilayer (composite / PEX-AL-PEX) pipe forms part of consumer piping — on new gas installs and on modifications to existing ones that contain multilayer pipe. For a Class 1a building, one accepted solution is an excess flow valve (EFV) conforming to DIN 30652-1 that latches shut on a full-bore rupture. The valve is sized so its nominal flow sits above normal running flow (no nuisance tripping) while still tripping on an open-end failure. The step most people miss: every protected branch must be able to generate enough open-end flow to actually trip the valve.
→ Use our free Gas Excess Flow Valve (EFV) Calculator to size a valve and run the per-branch rupture check in seconds.
Why Australia Introduced This Requirement
Multilayer pipe — the composite (PEX-AL-PEX) product a lot of us now run for gas — is quick to install and cost-effective. The catch is that, unlike copper, it can fail early at elevated temperatures. In a house fire, a compromised multilayer gas line can keep feeding the fire and cut down the time occupants have to get out. That fire-safety risk is exactly what drove the change to the Standard.
To address it, AS/NZS 5601.1:2022 introduced a requirement for fire emergency isolation wherever multilayer pipe forms part of consumer piping. It applies to new gas installations and to modifications of existing installations that contain multilayer pipe. The relevant clause is 5.2.11, and Amendment 1 (September 2024) tidied up the commissioning detail and confirmed the valve conformance standard.
What Clause 5.2.11 Actually Requires
In plain English, where multilayer pipe is part of the consumer piping, the installation has to be able to shut off the gas automatically if gas tightness is compromised. The Standard sets out a couple of routes:
- General method: a single class A safety shut-off valve (to AS 4629.1) that auto-isolates when de-energised, located before any multilayer pipe, as close as practicable to the gas supply point and readily accessible, with pressure proving of the downstream installation before gas is restored.
- Class 1a alternative: for a Class 1a building (a standard dwelling), a system or device(s) that automatically shut off the gas supply if gas tightness is adversely affected. This is where excess flow valves come in — an EFV senses excessive flow (the kind you get from a full-bore open end) and latches closed.
A few important notes from the clause: devices may sense either pressure loss or excessive gas flow (an EFV is the excessive-flow type); the fire emergency isolation requirement does not apply to multilayer pipe located only below ground external to a building; and where multiple devices are needed in a building, each must sit in an accessible location before the multilayer pipe it protects.
The EFV is not the only compliant path. For a Class 1a building you can also use a class A fire-interlocked safety shut-off valve, or simply run the affected runs in copper. For building classes other than 1a, a class A safety shut-off valve is required rather than an EFV.
When Do You Actually Need an EFV?
Ask yourself three questions on the job:
- Is there multilayer pipe in the consumer piping? If it's all copper above ground, Clause 5.2.11 doesn't bite.
- Is it a new install, or a modification to an existing install that contains multilayer pipe? Both are captured.
- What building class is it? Class 1a can use an EFV; other classes need a class A safety shut-off valve.
If the answers point to "multilayer pipe in a Class 1a dwelling", an EFV conforming to DIN 30652-1 is a deemed-acceptable solution — installed after the regulator and before any multilayer pipe it protects.
How to Size an Excess Flow Valve
Sizing an EFV is a balancing act. Get it wrong in either direction and you have a problem:
- Oversized → it won't trip in a fire, which defeats the purpose.
- Undersized → it nuisance-trips during normal use or purging.
The method the industry (including MPAQ's guidance) uses is:
- Sum the connected appliance load in MJ/h.
- Convert to a normal volumetric flow using the gas heating value — natural gas ≈ 38.7 MJ/m³, LPG (propane) ≈ 96 MJ/m³. Flow (m³/h) = load (MJ/h) ÷ heating value.
- Select a valve whose nominal flow (VN) comfortably exceeds that running flow so it won't nuisance-trip.
- Note the closing flow (VS) — EFVs close at roughly 30–45% above nominal under DIN 30652-1, so VS = VN × 1.30 to 1.45.
The DIN 30652-1 valve range (for example the SENTRY GS family) steps through nominal flows of roughly 1.6, 2.5, 4.0, 6.0, 10.0 and 16.0 m³/h, covering up to about 626 MJ/h on natural gas and around 1,000 MJ/h on LPG for several-appliance installations.
The Step Everyone Misses: The Per-Branch Rupture Check
Here's where a lot of installs come unstuck. A main EFV only latches shut once flow exceeds its closing flow. So for a fire on a given branch to trip the valve, a full-bore rupture on that branch has to generate more flow than the valve's closing flow.
Open-end (ruptured pipe) flow is roughly 2–3× the normal injector flow for that branch — that's a rule-of-thumb band; the exact figure comes from the Spitzglass formula for the actual bore, length and pressure. The problem: a small branch — say a single cooktop on a slim run — often can't generate enough flow to trip a main valve sized for the whole house.
Worked example: a 16 mm branch to a cooktop carrying ~137 MJ/h on LPG has a normal flow of about 1.42 m³/h. At 3× that's ~4.28 m³/h — below a ~5.07 m³/h closing flow, so a full-bore failure on that branch would not trip the main valve. Upsize that branch to 20 mm (~2.28 m³/h normal, ~6.8 m³/h at 3×) and it clears the closing flow. Where a branch can't be made to trip the main valve, the fix is to fit a dedicated EFV on that branch, upsize the branch, or run it in copper.
Do the maths in seconds
Our free Gas Excess Flow Valve Calculator does exactly this: enter your gas type and each appliance's connected load, and it picks the EFV up the DIN 30652-1 ladder, shows the nominal and closing flow, and flags every branch as OK / Marginal / Won't trip on a full-bore rupture — with advice on what to do about the ones that fail.
Installation and Commissioning Notes
- Install the EFV in an accessible location, before any multilayer pipe it protects, as close as practicable to the gas supply point (after the regulator).
- Purge at a controlled flow rate. If purge flow exceeds the valve's operating capacity the EFV will latch closed — that's by design, not a fault. Reset per the manufacturer's instructions.
- Never tamper with the valve — removing internals or seizing it with excess thread compound to stop it tripping is a serious compliance breach.
- Always size, locate and commission the valve to its DIN 30652-1 data sheet and confirm against AS/NZS 5601.1. Manufacturers' charts vary, so the actual valve data is what governs.
Common Mistakes to Avoid
- Oversizing the main valve so it never trips — bigger is not safer here.
- Skipping the per-branch check and assuming one main EFV protects every branch.
- Forgetting modifications count — adding multilayer pipe to an existing install triggers the requirement too.
- Treating the EFV as the only option when copper or a class A SSOV may suit the job better.
- Nuisance-trip "fixes" that involve tampering rather than correct sizing and controlled purging.
Summary
Fire emergency isolation for multilayer gas pipe is now a standard part of gas work in Australia. For Class 1a dwellings, a correctly sized excess flow valve conforming to DIN 30652-1 is a clean, deemed-acceptable way to comply — provided you size it so it won't nuisance-trip, and you confirm that every protected branch can generate enough open-end flow to actually trip it. When a branch can't, add a branch EFV, upsize, or run copper.
Don't do it on the back of a docket. Run the numbers with our free EFV calculator, then confirm against your valve's manufacturer data and AS/NZS 5601.1. Want it built into your workflow alongside AI standards lookups, pipe sizing and QLD compliance forms? Start your free 21-day TradeDesk trial.
This article is general guidance only and is not a substitute for the professional judgement of a licensed gas fitter. Always confirm requirements against the current AS/NZS 5601.1 and the valve manufacturer's DIN 30652-1 data.