Continuous flow and instantaneous hot water in Lake Macquarie

Updated October 2026

Continuous flow hot water, also called instantaneous hot water, is the system that never runs out. There is no tank. A compact wall-mounted unit heats water on demand as it flows through, so the fourth shower of the morning is as hot as the first. Lake Macquarie Hot Water connects you with licensed plumbers and gas fitters across the city who install, replace and repair continuous flow systems.

We are a referral service, not a plumbing business. The licensed hot water plumbers we work with handle the plumbing, with licensed gas fitters on gas units and licensed electricians on hard-wired electric units, as NSW requires.

How continuous flow works

When you open a hot tap, the unit senses the flow and fires a gas burner, or less commonly electric elements, around a heat exchanger. Water heats as it passes through and stops heating the moment you close the tap. No tank means no stored water going cold overnight, no standing heat loss, and no cylinder to corrode and flood the garage. Most units deliver water at a preset temperature, and many support bathroom controllers that let you dial in an exact temperature at the tap.

Why households here choose it

Endless hot water. Sized correctly, it keeps up with back-to-back showers, a bath and the dishwasher. That suits the larger family homes on the eastern lakefront and the holiday houses on the peninsula that go from empty to full in a weekend.
Space. The unit is the size of a small suitcase on an external wall. On the tight side passages of the older fibro and weatherboard stock around the ridge and the villages, that matters.
Lifespan. With no tank to corrode from the inside, continuous flow units commonly last 15 to 20 years with occasional servicing, versus 8 to 12 for a storage tank.
Efficiency. You only heat the water you use. For households on gas, running costs are typically lower than gas storage.

The first trade-off is fuel. A gas continuous flow unit needs adequate gas supply, and older or undersized gas lines sometimes need upgrading to feed a large unit. Natural gas is not available everywhere in Lake Macquarie, so check availability at your address before you compare quotes. Our gas hot water page covers that in more detail, including running one of these units on bottled LPG.

The second trade-off: these units live outside, in salt air

A continuous flow unit is almost always mounted on an external wall, which puts the whole appliance in the weather. In Lake Macquarie that weather is salty from two directions, and this is the part a writer who has only looked at a map gets wrong.

The lake is not fresh water. It is Australia's largest coastal saltwater lake, with a permanently open, trained entrance at Swansea and genuine tidal exchange, so the air off the lake carries salt in the same way the air off the ocean does. Add the surf side of the eastern suburbs and the Belmont peninsula, which has salt water on both sides, and a very large share of the housing here sits in it.

Salt attacks the casing, the flue terminal, the fasteners, the brackets and the external pipework and valves long before anything goes wrong inside. So the install decisions matter:

Mount it on a wall sheltered from the prevailing salt-bearing wind where the pipework allows, rather than on the most convenient wall.
Keep it clear of garden sprinklers and hose spray.
Ask about corrosion protection on the casing and marine-grade fixings, which cost little and buy years.
Have it serviced at sensible intervals rather than waiting for an error code, and rinse the casing with fresh water occasionally if you are close to the water.

Sizing: litres per minute, not litres

Continuous flow units are rated by flow, not capacity. As a guide, a 20L/min unit suits most two-bathroom homes, while 26L/min suits larger households likely to run two showers and a tap at once. Undersizing is the common mistake: the unit still works, but flow drops when multiple outlets run. Tell the plumber how many bathrooms you have and how your household actually uses hot water, and they will size it properly.

Repair or replace

Continuous flow units display error codes when something fails, which makes diagnosis fast. Igniters, sensors, valves and fans are all repairable, and on a unit under ten years old, repair is usually the right call. If the heat exchanger has failed on an older unit, replacement normally makes more sense. Swapping an old continuous flow unit for a new one on the same wall is one of the quickest hot water jobs there is, often done in a couple of hours.

Worth knowing on a salty street: a unit that is corroded on the outside but still firing is on borrowed time, because the fittings and the flue terminal fail before the burner does. If the casing has gone, get a replacement quote alongside the repair quote.

Cost and licensing

Installed pricing varies with unit size, flueing and whether the gas line needs upgrading, with gas systems as a category typically running about $1,200 to $3,500 installed in Australia, ex GST. A like-for-like continuous flow swap sits comfortably inside that range, while converting from a storage tank costs more because pipework and gas supply change.

In NSW, the plumbing must be done by a licensed plumber and gas connections by a licensed gas fitter. Hard-wired electric continuous flow units need a licensed electrician. Every tradesperson we refer holds the licences their part of the job requires, and licences can be checked with NSW Fair Trading.

Get a fast quote for continuous flow hot water from a licensed local plumber.

Frequently asked questions

Is continuous flow hot water really instant?

The unit heats instantly, but the hot water still has to travel from the unit to your tap, so there is a short delay, the same as with a tank. Units mounted close to the main bathroom, or paired with a recirculation setup, cut the wait.

What size continuous flow unit do I need?

For most two-bathroom homes, 20L/min. For larger households running multiple showers at once, 26L/min. Smaller 16L/min units suit one-bathroom homes and units. The plumber sizes it from your bathroom count and usage, which is worth getting right, as undersized units frustrate everyone every morning.

Will a continuous flow unit last on a lakefront street?

It can, but only if it is sited and specified for salt. The lake is salt water, so a lakefront wall is not the sheltered position people assume it is. Ask for a position out of the salt-bearing wind, corrosion-resistant fixings, and a service interval that suits a coastal install.

Can I replace my storage tank with continuous flow?

Usually yes, and it frees up the space the tank occupied. The job involves new pipework to the wall position, flueing and often a gas line check, so it costs more than a like-for-like swap and typically takes most of a day.

My continuous flow unit is showing an error code. What do I do?

Note the code, try turning the unit off and on at the isolation switch, and if the code returns, book a plumber. Codes map to specific faults such as ignition, sensors or flow, so the plumber often arrives knowing what part is likely needed.