Have you been wondering if learning how to flush a hot water system is really achievable? The honest answer is yes – with some important caveats.
But again – to be completely honest – it’s really not a complicated job. The tricky part is that we are talking about some pretty dangerous factors here:
- Hot water
- Pressure valves
- Electrical or gas components.
So while it’s easy to say “It’s a simple task,” it definitely also pays to know exactly what you’re doing before you start. So, in our guide, we’ll walk you through the full process in plain language … step by step.
First, a quick word on why flushing matters
Sediment – and we’re talking mostly minerals from your water supply – builds up at the bottom of your hot water tank over time. Left alone to fester, it does some things to your system that you really don’t want to happen.
- It reduces efficiency
- It increases energy costs
- It makes the system work harder
- It shortens its lifespan.
Definitely things you want to avoid, right? The good news is that a simple, regular flush keeps things running cleanly – and can add years to the life of your unit.
Most manufacturers (and hot water plumbers) recommend flushing at least once a year. And if you’re on tank water or in an area with particularly hard water, even more often is even better!
What you’ll need
Here’s the really simple part. All you need is:
- A garden hose long enough to reach a drain or outdoor area
- A flathead screwdriver
- A pair of gloves.
That’s genuinely it! Now let’s get into the 8-step process:
Step 1: Turn off the power or gas supply
Before you touch anything else, the heating element needs to be off.
- For electric hot water systems, switch the unit off at the circuit breaker – not just the thermostat.
- For gas hot water systems, turn the gas valve to the pilot setting rather than switching it off entirely, which avoids the need to relight the pilot afterwards.
Never (ever) work on a hot water system with the power or gas still running.
Step 2: Let the water cool
This is the step most people want to skip – but it’s one that matters a huge amount.
The water inside your tank can be extremely hot – hot enough to cause serious burns. So, give it at least an hour to cool down before proceeding.
Step 3: Connect your garden hose
Find the drain valve at the base of the tank – it looks similar to an outdoor tap fitting:
- Connect your garden hose securely
- Run the other end to a drain, a garden area that can handle hot water, or a bucket if you want to monitor what comes out.
Step 4: Open the pressure relief valve
Before you open the drain valve, open the temperature and pressure relief (TPR) valve on the side of the tank.
Why? It allows air into the system so the water can drain properly – without it, you’ll get a vacuum effect that slows or stops drainage completely.
The TPR valve will be on the side of the unit with a small lever.
But lift it carefully! If it’s stiff, worn or leaking when you open it, that’s a sign it needs replacing – a job for a licensed plumber.
Step 5: Open the drain valve and let it run
Open the drain valve and let the water flow. This is where knowing how to drain hot water system tanks properly pays off – because you shouldn’t be alarmed if the water initially runs discoloured or murky. That’s exactly the sediment you’re after!
Let it run until the water coming out is clear. For a heavily sediment-affected tank, this can take a while. For a well-maintained system flushed regularly, it moves more quickly.
Step 6: Flush with cold water
Once the tank is empty, briefly turn the cold water supply back on to flush out any remaining sediment hanging around at the bottom.
Learning how to flush hot water system sediment completely is the difference between a thorough job and one that leaves residue behind – and accelerates the necessary time between this flush and the next:
- Run the cold supply for a few minutes
- Then let it drain again
- And repeat if the water is still discoloured.
Step 7: Refill the tank
For this step:
- Close the drain valve
- Remove the hose
- Close the TPR valve.
After that, turn the cold water supply back on fully and let the tank refill. You’ll know it’s full when water flows steadily from a hot tap inside the house – open one to let air escape while the tank fills.
Step 8: Restore power or gas
Once the tank is full, restore power at the circuit breaker or return the gas valve from pilot to the on position. Give the system an hour or so to heat up before you expect hot water at the taps.
And that’s how to flush a hot water system Australia wide – the same process whether you’re in Brisbane or anywhere else, or whether it’s an electric or gas-based storage system – with minor variations for different unit brands and ages, of course.
A couple of things worth knowing
Knowing how to drain a hot water system is one thing – knowing when not to is another.
So here are a few signs that it’s worth getting a licensed plumber in before you put your knowledge about how to flush hot water tank systems into action:
- Your TPR valve is faulty
- Your drain valve won’t budge
- You notice corrosion around fittings
- Your system is older and hasn’t been serviced in years.
Because what begins as a straightforward flush can uncover underlying issues that need professional attention.
Similarly, if you want to know how to clean hot water system components beyond the tank itself – things like the anode rod, the inlet filter, the relief valve – that’s a job that really should be left to a professional as well. Those components affect the safety and longevity of the whole system, and getting them wrong is costly.
Having said that, we believe in you – you really can learn to flush hot water system tanks all by yourself. But if you’d simply rather have it done properly from the very start, S&J Plumbing and Gasfitting services hot water systems all across Brisbane Northside, Brisbane Southside, Logan, Moreton Bay, Redland Bay, and Ipswich, with same-day service, upfront pricing, guaranteed workmanship all included. Give us a call and we’ll take care of it.