Is It Better to Flush or Drain Your Water Heater? The Right Way to Prevent Breakdowns

Every year, thousands of water heaters fail not because they’re old, but because no one ever flushed them. If your shower turns rusty, your hot water runs out faster than it used to, or your heater makes loud popping noises, it’s not broken-it’s just full of sediment. The real question isn’t whether you should do something, but whether you should flush or just drain your water heater. And the answer isn’t what most people think.

What’s the difference between flushing and draining?

People use these terms interchangeably, but they’re not the same. Draining means letting water out of the tank-usually just enough to lower the level or prepare for replacement. Flushing means forcing water through the tank at high pressure to knock loose and remove built-up sediment.

Think of it like cleaning a coffee maker. Draining is pouring out the old coffee. Flushing is running clean water through the system to clear out the gunk stuck in the pipes. If you only drain your water heater, you’re removing the top layer of water, not the thick sludge settled at the bottom.

In Perth’s hard water areas-where mineral content runs high-sediment builds up fast. Calcium and magnesium from the water stick to the tank’s bottom and sides. Over time, this turns into a layer of sand-like grit. That layer doesn’t just sit there. It acts like insulation, forcing your heater to work harder. That means higher bills and a shorter lifespan.

Why sediment is the silent killer of water heaters

Most water heaters last 8 to 12 years. But if you’ve never flushed yours, it might not make it to five. Sediment doesn’t just reduce efficiency-it causes real damage.

• It traps heat against the bottom of the tank, causing the metal to overheat and crack.
• It forces the heating element (in electric models) or burner (in gas models) to run longer, burning out faster.
• It clogs the drain valve, making future maintenance impossible.
• It gets sucked into your pipes during use, causing low pressure and discolored water.

A 2023 study by the Australian Plumbing Institute found that homes with unflushed water heaters used 28% more energy than those flushed annually. That’s over $200 extra per year on electricity bills in Perth, just for the same amount of hot water.

Flushing: The only way to remove real sediment

If you want to remove the thick, gritty sludge at the bottom of your tank, you need to flush it. Draining won’t cut it.

Here’s how to flush your water heater properly:

1. Turn off the power. For electric heaters, flip the circuit breaker. For gas, turn the dial to "Pilot".
2. Turn off the cold water supply valve at the top of the tank.
3. Attach a garden hose to the drain valve at the bottom. Run it to a floor drain, outside, or a large bucket.
4. Open a hot water tap in your house to let air into the system.
5. Open the drain valve slowly. Let water flow until it runs clear. This can take 10 to 30 minutes.
6. Close the drain valve, remove the hose, and turn the cold water back on.
7. Wait for the tank to refill, then turn the power or gas back on.

You’ll know you’ve done it right when the water runs clear-not cloudy or brown. If it’s still murky after 20 minutes, you’ve got serious buildup. Don’t force it. Call a professional. A clogged valve could break under pressure.

When draining is enough (and when it’s a waste of time)

Draining is useful for one thing: reducing pressure before you replace the heater. It’s also fine if you’re just trying to lower the water level for a quick repair.

But if you’re doing it to fix dirty water, loud noises, or slow heating-draining alone won’t help. You’re only removing the water above the sediment. The grit stays. And it keeps doing damage.

Some people think draining once a year is enough. It’s not. You need to flush. Draining is like mopping the floor while leaving the dirt in the corners. Flushing is the pressure washer.

How often should you flush your water heater?

It depends on your water. In Perth, where water hardness ranges from 80 to 180 mg/L of calcium carbonate, flush your heater at least once a year. If you have very hard water (above 150 mg/L), do it every six months.

Here’s how to tell if you’re overdue:

• Your hot water smells like rotten eggs-sulfur bacteria feed on sediment.
• It takes longer than 15 minutes to heat up.
• You hear banging or popping when the heater turns on.
• Water from the tap looks cloudy or has orange/brown particles.

If you’re not sure about your water hardness, check your water bill. Most councils in Western Australia list it. Or buy a $10 test strip from Bunnings.

What happens if you never flush your water heater?

It doesn’t explode. But it dies slowly-and expensive.

Here’s what happens over time:

• Year 1-3: Slight drop in efficiency. You notice your bills creep up.
• Year 4-6: Sediment layer is 1-2 inches thick. Heating elements strain. Gas burners sputter.
• Year 7-9: The tank starts to corrode from the inside. The drain valve jams.
• Year 10+: The tank cracks. Water leaks. You’re paying for a new one-and maybe water damage to your floor.

Replacing a water heater costs between $1,200 and $2,800 in Perth. Flushing it costs $0-unless you need a new hose or valve. That’s a 100:1 return on effort.

Can you flush an old or rusty water heater?

Yes-but be careful.

If your heater is over 10 years old and the drain valve is stiff, don’t force it. Sediment may have fused to the valve. Forcing it open could snap it off, flooding your garage.

Instead, turn off the power and water. Open the valve slowly. If water trickles out, leave it. Call a plumber. They can use a special tool to clear the valve without breaking it.

And if your tank is visibly rusted on the outside? That’s a sign the inside is worse. Flushing won’t fix corrosion. You’re better off replacing it.

Flushing vs. installing a water softener

Some people think installing a water softener solves everything. It helps-but it’s not a replacement for flushing.

Softeners reduce new sediment. But they don’t remove what’s already there. Think of it like using a filter on a dirty river. The water coming out is cleaner, but the mud at the bottom of the riverbed is still there.

If you’ve got hard water and a 15-year-old heater, install a softener after you flush the tank. That way, you start fresh.

What to do if your drain valve won’t open

This happens more often than you think. Sediment locks the valve shut. Here’s what to do:

• Don’t use pliers. You’ll crack the valve.
• Try turning it with your hand, slowly. If it moves even a quarter turn, keep going.
• If it won’t budge, turn off the water, open a hot tap, and wait 24 hours. Sometimes pressure release helps.
• If still stuck, call a plumber. They can replace the valve for under $150.

Never ignore a stuck valve. It’s your emergency exit. If your tank ever leaks, you’ll need it to drain safely.

Final tip: Keep a record

Write down the date you flushed your water heater. Stick it on the tank with duct tape. Or use a free app like "Home Maintenance Tracker".

Why? Because you’ll forget. And next year, you’ll think, "I did this last year..."-and skip it. Sediment doesn’t care about your memory. It just keeps building.

Flushing your water heater takes 30 minutes. It saves you hundreds in energy bills. It prevents a flooded garage. And it could add 5 years to your heater’s life.

So don’t just drain it. Flush it. Your wallet-and your next hot shower-will thank you.