A continuous flow (instantaneous) gas water heater has three connections that need doing right every time: the gas inlet, the cold water inlet and the hot outlet. Doing them with a press-fit installation kit means isolation valves for both services arrive as a matched set, nothing needs a flame next to the unit, and the change-over is quicker than building it from loose fittings. Here's what's in these kits and how to read their ratings.
What a press installation kit does
An installation kit for an instantaneous gas heater bundles the ball valves for both gas and water, each with an outlet fitting to suit the heater's connections, and press ends to take the copper. Instead of threading a valve, adding a fitting and brazing or pressing a separate adaptor on each service, you press the copper straight into the kit and screw the outlet onto the unit.
Kits PSA stocks
Elson LF73722 — press union ball valve kit, G3/4 FI x DN20
The Elson LF73722 ($74.99) is a lead-free DR brass kit for continuous flow instantaneous heaters, with a G3/4 female connection and DN20 press end. Its published specs are worth reading closely:
| Water ball valve | Gas ball valve | |
|---|---|---|
| Pressure rating | 1600 kPa | 500 kPa (valve body) |
| Max temperature | 99°C | 95°C |
| Certification | WaterMark WMKA21922, AS 5830.1; AS/NZS 4020 | AGA8350, AS 4617 |
Other features: lead-free DR brass, T handles, full-flow ball, and union connections so the heater can be removed later without cutting pipe.
AVG QIKP-1-LF — Quickie Universal Press Kit
The AVG Quickie Universal Press Kit ($62.06) bundles the fittings for installing or replacing an instantaneous gas continuous flow unit using universal press-fit connections. Lead-free construction, from Australian Valve Group (a Watts Water Technologies brand). Check the listing for the exact components against your unit's connections.
Reading the ratings properly
- Two certifications, two services. The water valve carries a WaterMark; the gas valve carries a gas (AGA) certification. That's the same principle covered in why water and gas press fittings aren't interchangeable — one kit, but each valve is approved for its own service.
- Gas valve pressure is lower, and that's normal. 500 kPa is far above domestic gas supply pressures; it isn't comparable to the 1600 kPa water rating and doesn't need to be.
- Temperature limits matter on the hot side. The water ball valve is rated to 99°C. Check where each valve sits relative to the heater outlet and the unit's maximum delivery temperature.
Before you order: match the unit
- Check the heater's installation manual for gas and water connection sizes and thread types. Kits come in different size and thread combinations; the one that suits a 20mm gas run and a G3/4 connection won't suit everything.
- Check the gas pipe size against the appliance's gas consumption and run length — a continuous flow unit is usually the biggest gas load in the house.
- Check your press fittings for the rest of the run: gas-rated copper press gas fittings on the gas side and copper press water fittings on the water side. For transitions to threaded outlets elsewhere, see our lugged elbow guide.
Compliance reminders
Gas connection and commissioning is licensed gasfitting work to AS/NZS 5601.1; the heated water installation follows AS/NZS 3500.4 and the manufacturer's instructions, including any temperature control requirements for the outlets served. Leak test both services and commission the unit before handover.
Need standalone press ball valves for other parts of the job? See butterfly, lever, extended or union, or browse the press union ball valve kits and lead-free press ball valves.
Frequently Asked Questions
What is a continuous flow hot water installation kit?
A matched set of gas and water isolation valves with outlet fittings that suit an instantaneous gas water heater's connections. Press versions let you press the copper straight into the kit.
Why is the gas valve rated at a lower pressure than the water valve?
Gas supply pressures are far lower than water pressures. The Elson LF73722 gas valve body is rated to 500 kPa, well above domestic gas pressures, while its water valve is rated to 1600 kPa.
Are press continuous flow kits certified for both gas and water?
Each valve is certified for its own service. The Elson LF73722 water valve carries WaterMark WMKA21922 (AS 5830.1) and the gas valve carries AGA8350 (AS 4617).
Can I install a continuous flow gas unit myself?
The gas connection must be done by a licensed gasfitter, and the water connection by a licensed plumber, following AS/NZS 5601.1, AS/NZS 3500.4 and the manufacturer's instructions.