How To Flush A Hot Water System (And Why It Matters)

Your hot water system does its job quietly and diligently every single day – delivering warm showers, clean dishes, and steady comfort all year round. But without regular maintenance, even the most reliable unit bearing the name of the best brands in Australia can start showing signs of wear. One of the most important things you can do to extend its lifespan and performance? Learn how to flush a hot water system.

So, if you’re wondering how to flush hot water system equipment safely and effectively – especially here in Brisbane, where hard water is really common – you’ve found the right place! We’ll walk you through exactly:

• How it’s done
• Why it matters
• And when it’s time to call in the pros.

Why flushing your hot water system is essential

Over time, minerals like calcium and magnesium in your water supply settle at the bottom of your tank. This build-up of sediment can:

• Reduce efficiency (your heater works harder = higher bills)
• Lower hot water capacity
• Shorten the life of the system
• Create rumbling or knocking sounds in the tank
• Lead to discoloured or metallic-smelling water.

Flushing hot water system units removes these sediments, restores performance, and helps prevent breakdowns. It’s one of the most overlooked maintenance tasks – but it’s critical for long-term reliability.

How often should you do it?

For most Brisbane homes, a flush every 12 to 24 months is ideal – although some units (especially those in areas with hard water) may benefit from more frequent maintenance.

Unsure? A fully licensed hot water plumber in Brisbane can assess your system and recommend a plan.

So let’s get straight into it:

How to flush a hot water system: An easy 7 step guide everyone can follow

Here’s our exclusive insight into how to flush a hot water system safely at home – with no plumber in sight!

BUT PLEASE NOTE: If you’re not confident working with plumbing or electricity/gas connections, or you’re unsure about compliance and insurance issues, skip it all and call in a licensed professional instead.

For the rest of you, let’s get into it:

1. Turn off the system

• For electric hot water units, switch off the circuit breaker.
• For gas hot water models, turn the gas control valve to ‘pilot’ or completely off.

This step ensures no helpful-but-dangerous energy is being supplied during the process.

2. Turn off the cold water supply

This is usually located near the top of the tank. Turning it off prevents more water entering the system during flushing.

3. Open a hot water tap

Bear with us, because this is an important step:

• Choose any hot tap in your home
• Open it up, and leave it open.

It sounds simple and pointless, but it helps relieve pressure in the tank and allows the system to drain more easily.

4. Connect a hose to the drain valve

Find the drain valve near the bottom of your tank and attach a standard garden hose – it’s not difficult. Now:

• Run the hose to a safe drainage point
• This should be somewhere outside, but it may be a floor drain if you’re careful.

And now, be extra-extra careful, because the water will almost certainly be extremely hot!

5. Open the drain valve

Is the hose secured and in place?:

• Open the drain valve.
• Allow the water to fully drain from the tank.

Are you wondering how to drain hot water system tanks completely – Step 5 is exactly where it happens! It may take several minutes, depending on the size of your unit, but it will happen.

6. Flush with cold water

Now that the tank is empty, turn the cold water supply back on for somewhere between 30 seconds to a minute. This helps stir up and flush out any remaining sediment.

Then turn the water off and let it drain again. You can repeat this a couple of times for a thorough clean.

This is essentially how to flush water heater systems clean and clear of debris.

7. Close everything & refill

But wait! There’s one final step:

• Turn the drain valve off
• Remove the hose
• Turn the cold water supply back on
• Once water flows steadily from your open hot water tap, close it
• Restore power (or gas) to the unit.

Now, give yourself a pat on the back – because you’ve just completed a basic flush hot water system procedure!

Extra advice for Brisbane homes

You’re probably here because you were looking for how to flush a hot water system Australia style. Well, here’s the good news – the process is basically the same no matter where you are! But in Brisbane and beyond, it’s extra important to account for our high mineral content water, especially in rural areas. That means more sediment, and more need for regular flushing.

Also, if you’re on tank water or use a solar hot water system, you may need a customised maintenance plan. It’s worth speaking to your friendly local plumber to ensure you’re flushing your system the right way for your setup. And remember: You also need to check if this sort of procedure is even allowed by your local authorities, because all those regulations are so hard to navigate these days.

Don’t forget to check the anode

A good flush removes the sediment, but your system’s sacrificial anode is something else entirely! This cheap and ingenious innovation prevents corrosion inside the tank, and it should be checked every few years – and especially during a flush. Replacing it when worn out can double your system’s lifespan – so never forget it!

Not feeling confident?

Does it all sound a bit too hands-on for your liking? Or, if your system has signs of wear and age, it’s also best to book a licensed hot water plumber. Trying to DIY beyond your comfort zone could lead to leaks, burns, system damage, or compliance issues.

That said, if you’re just looking for how to clean hot water system units as part of responsible home maintenance, and you’re confident in the process, a flush is a great place to start.

When to call a professional

If you notice any of the following, flushing alone might not be enough:

• Water still appears dirty after a flush
• Pressure hasn’t improved
• You hear banging/rumbling noises regularly
• Hot water runs out too fast.

These are all potential signs of deeper and more complex issues, like a failing thermostat, a worn-out anode, or excessive sediment build-up. A full system service or replacement might be needed in these cases.

If you’ve looked into how to drain a hot water system Australia -style and you’re still aren’t sure where to begin, a professional can safely handle everything from draining and flushing to full replacements. So – what should you do next?

Ready to flush? Or thinking replacement?

Need help with flushing hot water system units at your place? Or maybe you’re ready to explore your upgrade options? The friendly team at S&J Hot Water Brisbane are always here to help. Our fully-licensed hot water plumbers service Brisbane Northside, Brisbane Southside, Logan, Moreton Bay, and Redland Bay, offering:

• Expert repairs
• Maintenance
• Full hot water system replacements.

And it all comes with fast turnaround and fair, affordable prices for our difficult times. So – call us now or submit your online enquiry to keep your system running at its best for years and years to come.