A Rinnai continuous flow system heats water only when you turn on a hot tap, so it never runs out and there’s no tank to keep hot. The unit is small enough to mount on an outside wall, which suits Inner West terraces with tight courtyards and side passages. It’s a great fit for many homes, as long as you choose the right size and already have gas connected.
We install, repair, and replace continuous flow units as part of our hot water work across the Inner West, and Rinnai is the brand we recommend most. Here’s why, how to choose the right model, and when a heat pump is the better call.
How continuous flow hot water works
A continuous flow unit, sometimes called instant or tankless hot water, has no storage tank. When you turn on a hot tap, water flows through the unit, a sensor detects the flow, and a gas burner heats the water as it passes through a heat exchanger. When you turn the tap off, the burner switches off.
Because there’s no tank, there’s nothing to reheat overnight and no stored hot water slowly cooling down. Rinnai lists the main benefits as:
- compact design that can save space around the home
- continuous hot water without a storage tank
- heating water only when it’s needed, which can improve energy efficiency
- no heat loss from storing hot water in a tank
Why we recommend Rinnai
Every brand has its fans. These are the reasons we keep coming back to Rinnai after two decades of installs:
- Easy to service: Rinnai units are widely used across Sydney, so parts and service support are easy to get. That means less waiting when something needs fixing.
- Efficient: the Infinity B26 carries a 6 star energy rating, the highest the label allows.
- Long warranty: Rinnai offers a 25-year heat exchanger warranty on the B26, made up of a 12-year standard warranty plus a 13-year extension if you join its scheduled service program.
- Proven design: Rinnai calls the Infinity range Australia’s first fully electronic gas continuous flow system, and the B26 Australia’s favourite.
- Steady temperature: its Puretemp technology helps keep the water temperature stable as the flow changes.
Does continuous flow really cost nothing when it’s off?
Not quite, but close. When no hot tap is running, the unit doesn’t burn any gas, and there’s no tank losing heat all day. That’s the big saving over a storage system.
There are still two small costs to know about:
- electricity: the unit plugs into a power point for its electronic controls, so it uses a small amount of power even on standby
- gas supply charge: your gas retailer charges a daily supply fee whether you use gas or not
For most homes that already have gas for cooking or heating, the supply charge is already being paid, so continuous flow adds very little to it.
Which size do you need?
Continuous flow units are sized by how many litres of hot water a minute they can deliver. Too small, and the shower runs lukewarm when someone else turns on a tap. Rinnai’s sizing guide, based on 3 star water-efficient outlets, suggests:
- Infinity B12, B16, and B20: one bathroom
- Infinity B26: two bathrooms, or three in warmer climates
- Infinity 28i (installed indoors): one or two bathrooms, or three in warmer climates
- Infinity 32: two or three bathrooms, or four in warmer climates
Rinnai notes that flow can be limited if several taps or showers run at the same time, and that older showerheads with higher flow rates may need a larger unit. We size every system to how your household actually uses hot water, not just the number of bathrooms.
Continuous flow and Inner West terraces
Terraces are where continuous flow really earns its keep. A storage tank takes up a big chunk of a narrow side passage or courtyard. A continuous flow unit mounts flat on the wall, often in a spot where nothing else would fit.
A few things to plan for:
- flue clearances: gas units need clear space around the flue, away from doors, neighbouring openings, and windows. We can overcome most clearance issues by fitting a side flue.
- gas supply: the gas pipe and meter must be big enough to run the unit at full flow, and some older homes need an upgrade
- power: the unit needs a weatherproof power point nearby
- upstairs bathrooms: in a long terrace, hot water can take a while to reach a bathroom at the far end, so placement matters
Don’t rule out continuous flow because your side passage is narrow or the best spot on the wall is close to a window. A side flue redirects the exhaust sideways, away from the opening, so the unit can still meet the clearance requirements. It’s one of the most common ways we make continuous flow work in tight terrace spaces.
We handle the gas fitting as part of the install, and we’ll tell you upfront if your gas supply needs work. We’ve fitted units in terraces across Annandale, Newtown, and Stanmore, where space is always tight.
Temperature and tempering valves
Most Rinnai models come in 50°C and 60°C versions. The 50°C models are factory preset for homes, so the water reaching your shower isn’t hot enough to scald.
NSW Fair Trading says that when you replace a hot water heater, a temperature control device, such as a tempering valve, must be fitted to control the temperature at bathroom fixtures. A unit that’s factory preset for bathrooms doesn’t need one. We’ll recommend the right setup for your home.
There’s one more bonus. Continuous flow units have no tank relief valve to test every six months, unlike the storage systems in our relief valve guide.
When a heat pump is the better choice
We’re happy to recommend something other than Rinnai gas when it suits you better. A heat pump draws heat from the air to warm a storage tank, running on electricity instead of gas. It’s often the better call if:
- you don’t have gas connected, and don’t want to add it
- you have rooftop solar, so you can run the heat pump on your own power during the day
- you’re planning to go all-electric
Many Inner West households are heading that way. The council has published a case study of a Leichhardt couple who kept their working instant gas hot water while they got quotes for a heat pump, to make their home fully electric. Inner West Council has also moved to extend its all-electric planning rules to hot water in new homes, according to 350 Australia’s council tracker. If you’re building new or doing a major renovation, check what your development consent requires.
Heat pumps need space for the tank and good airflow, and their fans can be noticed by close neighbours. We’ll talk you through both options honestly.
Frequently asked questions
Is continuous flow cheaper than a storage hot water system?
Often, yes, because it only heats water when you use it and there’s no tank losing heat. Your actual savings depend on your gas and electricity prices, how much hot water you use, and the system you’re replacing.
What size Rinnai do I need?
As a guide, the Infinity B26 suits most homes with two bathrooms, and smaller models suit one bathroom. Older high-flow showerheads or several showers at once may need a bigger unit, so we size it to how you use hot water.
Can a continuous flow system run two showers at once?
Yes, if it’s sized correctly. A 26 litre unit can usually run two showers with 3 star water-efficient showerheads. A smaller unit may struggle.
What if there isn’t enough clearance for the flue?
In most cases, we can fit a side flue. It directs the exhaust sideways, away from nearby doors and windows, so the unit meets the clearance requirements even in a tight side passage or close to an opening.
Can I get continuous flow without gas?
Yes. Rinnai also makes electric continuous flow units, but they need three-phase power, which many homes don’t have. If you don’t have gas, a heat pump is often the more practical choice.
Book a Rinnai continuous flow installation
Richard Knight Plumbing has been installing and servicing Inner West hot water systems from our base on Raper Street, Newtown, since 2005. We can size the right Rinnai unit for your home, handle the gas fitting and installation, and give you honest advice if a heat pump would suit you better.
We work Monday to Friday, 7 am to 5 pm, across all the suburbs on our service area page. Call 1300 300 941 or request a quote, and we’ll get back to you with clear advice and an obligation-free quote.