National Water Week on a septic and tank property: the water-wise swaps worth making

When your house runs on its own rainwater tank and septic system, every litre you don't use stays in your tank and never reaches your septic, and the biggest savings come from the shower, the toilet and the washing machine.

Why water-wise matters more on a septic and tank property

If your house drinks from a rainwater tank and drains to a septic system, being water-wise isn't really about a bill. A litre you don't use stays in your tank for next week. It is also one less litre your septic tank and absorption trench have to take.

Your property is its own water supply and its own sewage works. Every saving lands at home twice.

National Water Week is a good moment to look at this. The Australian Water Association hosts National Water Week, and the 2026 week falls on 19 to 25 October under the theme "Water is Life". Most water-saving advice is written for houses on town water. Here is how it translates when the water comes off your roof and leaves through your own tank and trench.

This applies whatever system sits in your yard. The NSW Office of Local Government's The Easy Septic Guide uses "septic systems" to cover all on-site sewage systems, including pump-outs, composting toilets and aerated systems.

At Ward Septics we see the other end of the pipe every working day: the septic tanks and rainwater tanks we pump out and clean across the Central Coast and Lower Hunter. The less water that goes down the drain, the less the system has to handle. That is a gentler load on the tank, the trench and any pumps in between.

Which fixtures use the most water, and what a better one saves

The biggest water users in the home are washing machines, showers, taps and toilets, and products are rated up to 6 stars. The government's own comparisons show where the litres go:

• Shower. Swapping a 15 L/min shower for a 5-star 6 L/min one saves about 105 kL a year for a family of four.
• Toilet. Replacing an old 12 L single flush with a 4-star 3.5 L toilet saves about 50 kL a year for a family of four. Using the half-flush button gets the most from it.
• Washing machine. An 8 kg 5-star machine using 55 L a load, instead of a 3-star using 115 L, saves a family 18 kL a year. The label shows litres per load.
• Taps. Low-flow taps and aerators can cut flow from 15 to 18 L/min down to as little as 2 L/min.
• Dishwasher. For 14 place settings, a 6-star model uses 9.5 L a wash against 17 L for a 3-star. That is 7.5 L less every wash, by our working (17 minus 9.5).

Yearly water saved by one swap (kilolitres)

Add the three yearly figures together and a household with an old shower, an old single-flush toilet and a 3-star washer could be sending around 173 kL a year more than it needs through the septic. That is our estimate: 105 plus 50 plus 18, or roughly 470 litres a day (173,000 divided by 365). The source figures use slightly different households, so treat it as a rough guide, not a measurement.

Those comparisons are often quoted in dollars, but dollars assume town water. On a tank, the litres are the number that matters.

How much would a new showerhead save your household?

The shower is the biggest single swap on the list. The rule of thumb from the same guidance is that every 1 L/min difference is worth nearly 12 kL a year for a family of four.

You will find a shower's flow rate on its WELS label. For one already installed, look the model up on the WELS product register. Take the new shower's flow rate away from the old one and multiply the difference by 12 kL for a rough yearly saving. Going from 15 to 6 L/min is a 9 L/min difference, which lands close to the government's 105 kL figure above.

What you can change yourself, and what needs a licensed plumber

Some of these swaps are a Saturday job and some are not. Householders can legally replace a bathroom tap valve or a showerhead. Toilet suites and other WaterMark-certified plumbing products must be installed by a licensed plumber.

Two traps sit alongside that:

• Don't remove the flow-control device from a fixture. It defeats the efficiency you paid for.
• Non-certified products may affect your insurance cover if the product fails.

The plumbing products you buy today will likely be used for over 10 years.

The Water Rating scheme (WELS) covers taps and showers, toilets and urinals, dishwashers and washing machines, and flow controllers. Those products must be registered and labelled to be sold, so the star rating is always there to check.

The label matters because you live with the choice. As the scheme puts it, the plumbing products you buy today will likely be used for over 10 years.

How to run a Water Night on a septic system

Water Night is held every year on the Thursday of National Water Week. In 2026 it is 5 to 10pm on Thursday 22 October, on the national events calendar. Households turn off their taps and running water for those five hours.

Water Night is held every year on the Thursday of National Water Week. 2026: Thursday 22 October, 5 to 10pm.

1. Before 5pm Fill water bottles and the kettle.
2. 5pm Taps and running water off.
3. Through the evening Flushing the toilet is fine; note each time you reach for a tap.
4. 10pm Taps back on.
5. Next day Jot what you noticed on the maintenance log sheet in The Easy Septic Guide.

It suits a septic home well, because the toilet is allowed. The organisers' own answer to "Can I flush the toilet?" is "Yes." You can fill bottles and the kettle beforehand. The point is to notice your automatic tap habits, not to go without.

Treat it as a quiet night for your system. Every time your hand reaches for a tap and stops, that is water that would have gone from your tank, through the house and into the septic. Most people are surprised how often it happens.

It is voluntary, and you don't need the official date. Any evening you choose works the same way.

Write down what you noticed. The Easy Septic Guide includes a maintenance log sheet, and a Water Night note sits well beside your service dates.

Where drips and running cisterns hide

A slow leak on a septic property costs you twice: once from the tank and again in the trench. Leaks are worth hunting even when they look trivial, because they run all day and all night.

• The cistern. A toilet that keeps trickling into the bowl sends water to the septic around the clock. Put a few drops of food colouring in the cistern and don't flush for a while. Colour in the bowl means it is leaking.
• The pressure pump. On tank water, Water Night doubles as a leak test. If the pump kicks in while every tap is off and nobody has flushed, water is going somewhere.
• Dripping taps. Inside, a worn bathroom tap valve is one you can replace yourself. Outside, check the garden tap at the base of the tank, where a drip can go unnoticed for months.

Cistern repairs and toilet suites are work for a licensed plumber.

Rainwater tank owners: what a litre saved is worth

Efficient fixtures add up. The 2025 evaluation of WELS estimates the average household saves 35 litres a day, with 2,060 GL saved nationally since 2006.

On town water, that is a smaller bill. On a tank, it is water still in your tank. Our estimate: 35 litres a day for a year is about 12,800 litres (35 times 365) left in the tank rather than sent to the septic.

35 litres a day

The average household saving from WELS in 2025, per the 2025 evaluation of the scheme.

That matters more in a dry spring. We have covered rainwater tanks in a drier spring and the Central Coast water restrictions in earlier pieces on the Ward Septics blog. If your water comes off the roof, a clean tank is part of the same habit; see our water and rainwater tank cleaning page.

Water leaving the house can work for you too. Our guides to disposing of greywater safely on rural properties and growing a garden around your septic system cover what goes where.

Every swap and its saving on one page

Source: energy.gov.au, waterrating.gov.au, Water Night

Three things to do next, and when to call Ward Septics

1. Check for leaks. Look at the cistern, the taps and the garden tap at the tank, and listen for a pump that starts with nothing running.
2. Run your own Water Night. Taps off from 5 to 10pm, kettle and bottles filled first, flushing allowed.
3. Read the label before you buy. Check the star rating and the litres on any tap, shower, toilet, dishwasher or washing machine, or look it up on the WELS product register.

1. Check for drips, a running cistern and a pump that starts with every tap off.
2. Run your own Water Night, 5 to 10pm, kettle and bottles filled first, flushing allowed.
3. Check the WELS star rating and litres on the label, or on the product register, before you buy a tap, shower, toilet, dishwasher or washing machine.

A week of thinking about water is also a natural time to look at the tanks themselves. Ward Septics is owner-operated and does septic tank pump-outs, septic tank cleaning and rainwater tank cleaning across the Central Coast and Lower Hunter. With 90 metres of hose, we reach the tank without driving on your property.

If your septic or rainwater tank is due, call Ward Septics on 0438 315 514 and we'll work out a time that suits you.

Sources

• https://www.nationalwaterweek.org
• https://www.nationalwaterweek.org/events/nww-events
• https://waternight.com.au/about-water-night/
• https://waternight.com.au/water-night-for-households/
• https://www.waterrating.gov.au/consumers/water-rating-scheme
• https://www.waterrating.gov.au/resources/review-evaluation/environmental-effects
• https://www.energy.gov.au/households/water-efficiency
• https://www.olg.nsw.gov.au/sites/default/files/2026-02/the-easy-septic-guide.pdf