Continuous flow gas hot water: a plain-English buyer's guide

A continuous flow gas system, sometimes called instantaneous or tankless, has quietly become the default hot water choice for gas-connected homes across Western Sydney. Instead of keeping a big tank of water hot around the clock, it heats water only at the moment you turn on the tap. That simple difference is why it never runs out and why it is cheap to run. Here is what you need to know before buying one.

How continuous flow actually works

When you open a hot tap, water flows through the unit and past a gas burner that fires up instantly and heats it on the way through. Turn the tap off and the burner shuts down. Nothing is stored, so there is no tank slowly losing heat and no energy wasted reheating water you are not using. You also get hot water for as long as you want it, which is why big families rarely run cold with one. You set the temperature on a controller, and the unit delivers that same temperature every time.

Getting the size right, in litres per minute

Continuous flow units are not sized by tank volume, because there is no tank. They are rated by flow rate in litres per minute, which is how much hot water they can deliver at once. Get this wrong and you will feel it whenever two taps run together. As a rough guide:

• One bathroom home: around 16 to 20 litres per minute.
• Two bathrooms: around 24 to 26 litres per minute.
• Three or more bathrooms: 32 litres per minute.

The number that really matters is how many hot outlets might run at the same time, not just how many bathrooms exist on paper. A household that showers while the dishwasher and laundry run needs more capacity than the bathroom count alone suggests.

The brands worth knowing

A few names dominate for good reason. Rinnai's Infinity range is the long-standing benchmark for continuous flow in Australia, known for reliability and easy servicing. Rheem's continuous flow units, including the 26 and 32 models, sit right alongside it and share a strong Sydney parts network. Bosch is a respected third option with a solid track record. Across all three, the deciding factor is often parts availability, because a unit with parts on every local shelf gets fixed faster when it eventually needs attention.

Continuous flow versus a storage tank, and what to check before install

Against a storage tank, continuous flow wins on running cost, endless hot water and a long 15 to 20 year lifespan, and it takes up far less wall space. The trade-offs are honest ones. The up-front price is higher than a basic electric tank, roughly 1,900 to 3,500 dollars fitted. It needs an adequate gas supply, and an older home may need its gas line upgraded to feed the unit properly. There can be a slight lag before hot water reaches a distant tap, and a very low flow, like a barely-open tap, may not trigger the burner.

Fitting a continuous flow unit is licensed gas work. It is not a DIY job, both for safety and because gas work must be carried out and certified by a licensed gas fitter. Terry holds NSW plumbing and gas fitting licence L10959 and has fitted these units across Berala, Auburn, Lidcombe and the wider inner west since 1986. He will size the unit properly for your household and check your gas supply before quoting a fixed price. Call Terry on 0415 274 542 to talk it through.