Why is my Hot Water System Leaking and How to Fix it Fast

Last updated on October 24, 2025

Just imagine it’s a chilly Aussie morning, you’re craving a long, hot shower… but instead, you step into a puddle near your water heater. That sinking feeling? Priceless.

You mutter a few choice words, grab a towel, and stare at the tank: Your hot water system is leaking.

Take a deep breath.

A leaking hot water system doesn’t always mean disaster.

In most cases, it’s something small:

A loose valve, worn-out fitting, or a pressure issue you can fix without calling in half the tradies in your suburb. Other times, it’s your tank politely telling you, “Hey, I’ve had a good run; maybe it’s time for retirement.”

In this guide, we’ll explain:

Why your hot water system is leaking
How to find where the leak’s coming from
What you can safely fix yourself
When to call a plumber
And how to prevent leaks in the future

Let’s dive in (not literally, please; the floor’s already wet enough). But in our article

Common Reasons Your Hot Water System Is Leaking

If you’re seeing puddles or drips around your tank, the cause could be anything from pressure buildup to corrosion. Here are the top offenders behind an Aussie homeowner’s dreaded “hot water system leaking” moment:

☑️ The Temperature & Pressure Relief (TPR) Valve

This little valve is your tank’s safety guard; it releases extra heat or pressure.

If you see it dripping constantly, it may be faulty or full of mineral deposits.

How to Fix: Turn off the power and cold-water inlet, lift the valve’s lever for a few seconds to flush out debris, and see if it stops. If not, replace the valve (about $30–$60). Always wrap the threads with Teflon tape for a tight seal.

☑️ Loose Inlet or Outlet Connections

Hot water systems expand and contract over time. The inlet (cold water) and outlet (hot water) fittings at the top may loosen, causing slow leaks.

How to Fix: Turn off power, tighten gently with a wrench, and reseal with plumber’s tape if needed. Avoid overtightening, which can crack fittings and worsen the leak.

☑️ A Leaking Drain Valve

This valve, found near the bottom, lets you flush the tank for cleaning. But if it’s not closed tightly or has worn threads, it’ll drip.

How to Fix: Close it snugly. Still leaking? Attach a garden hose cap or replace the valve entirely; cheap, quick, and effective.

☑️ Internal Tank Corrosion

If you notice rust stains or reddish water, your tank might be corroded inside. Once corrosion eats through the lining, leaks follow, and no patch can fix that.

How to Fix: Sadly, that’s a replacement job. A standard 250L electric system costs around $1,200–$1,800 installed in 2025.

☑️ Excessive Water Pressure

If your mains water pressure is too high (above 500kPa), it can trigger your safety valves to constantly leak.

How to Fix: A plumber can install a pressure-reducing valve for $200–$350. It’ll save your system (and your sanity).

☑️ Condensation (the Sneaky “Fake Leak”)

Sometimes your “hot water system leaking” isn’t leaking at all; it’s just condensation forming on the cool tank surface.

How to Fix: Wipe it dry and watch for new moisture. If it reappears evenly across the surface, it’s likely condensation. Improve ventilation or insulate nearby pipes to reduce it.

How to Diagnose a Hot Water System Leak (Step-by-Step)

Before calling a plumber, grab a towel, flashlight, and your detective hat. Here’s how to find where the leak’s coming from:

Leak Point	Location on Tank	Appearance of Leak
Drain Valve Leak	Located at the very bottom edge of the tank. It is usually a brass or plastic valve with a threaded spout (where a garden hose is attached for draining).	Drips or a slow stream of water coming directly from the valve spout or the stem.
T&P (Temperature and Pressure) Relief Valve Leak	Located high up on the side of the tank, usually near the top. It has a discharge pipe (a metal or plastic pipe) running down the side of the tank, often ending a few inches above the floor.	Water drips or runs out of the end of the discharge pipe.
Corrosion/Pinhole Leaks	Can occur anywhere on the main body of the metal tank, though often first appear near the bottom where sediment settles and corrosion is accelerated.	Tiny, isolated streams or pin-sized drops of water coming directly through the side of the metal jacket.

1. Turn off the power and cold-water supply.

Electric: Switch off at the circuit breaker.
Gas: Turn the dial to “Pilot” or “Off.”

2. Dry everything around the tank.

Mop or towel up any standing water and wait 10 minutes. New drips will show you the source.

3. Check the top of the tank.

Look at the inlet, outlet, and valves for moisture.

4. Inspect the sides and base.

Rust or bubbling paint near the bottom usually means internal corrosion.

5. Examine nearby pipes and walls.

Sometimes, it’s not your tank at all. A leaking pipe or condensation from another source might be fooling you.

What You Can Fix Yourself (Safely)

plumber fixing the leaking hot water tank

Australia loves a bit of DIY spirit, but remember: Water + electricity = danger.

Here’s what you can and can’t do safely when your hot water system is leaking:

✅ Go Ahead and Try:

Replacing a TPR valve or drain valve
Tightening loose fittings
Replacing flexi hoses
Flushing sediment buildup once power is off
Cleaning rust or debris around the base

❌ Leave to the Pros:

Anything involving electrical panels
Gas line adjustments or disconnections (illegal without a gasfitter’s licence)
Internal tank corrosion repairs (not possible)
Persistent leaks after DIY fixes

If in doubt, call a licensed plumber. It’s safer and cheaper than a flooded garage.

When to Replace Instead of Repair

If your hot water system keeps leaking despite repairs, it may be waving a white flag.

Tell-tale signs it’s time to replace:
Water is constantly pooling under the tank
Rust or brown water
Weak hot-water pressure
The tank is over 10 years old
Frequent valve replacements
If yours is older, replacement is usually more cost-effective than ongoing repairs.

Prevent Future Hot Water System Leaks

Want to stop future leaks before they start? Follow these simple maintenance tips:

Flush the Tank Annually

Attach a hose to the drain valve and run cold water through until it flows clear. This removes sediment and prevents pressure issues.

Test the TPR Valve Every 6 Months

Lift the lever slightly to ensure it releases water, then reseats without dripping.

Inspect the Anode Rod

This metal rod sacrifices itself to prevent corrosion. Check every 3–5 years if half gone, replace it.

Set the Thermostat to 60°C

This is hot enough to prevent bacterial growth but not so hot that it stresses the system.

Keep It Ventilated

Good airflow prevents condensation and corrosion, especially if your system is in a garage or cupboard.

When to Call a Plumber

Call a licensed professional if:

The tank itself is leaking
You smell gas
There’s electrical arcing, or the breaker trips
You can’t identify where the leak’s coming from
The system is under manufacturer’s warranty

How to Find a Licensed Plumber

Check the official Australian government register:

https://www.licencerecognition.gov.au
Or search through your state’s plumbing authority (e.g., QBCC, PIC, VBA).

Always ask for a written quote, and ensure they dispose of your old unit responsibly.

Upgrading to a Modern, Leak-Resistant System

If your old tank’s on its last legs, consider upgrading to something modern, energy-efficient, and eco-friendly.

Heat Pump Hot Water Systems

Use air energy instead of direct electricity
Up to 70% cheaper to run
Great for most Aussie climates
Eligible for generous rebates

Solar Hot Water Systems

Ideal for sunny regions like QLD, NSW, and WA
Cut energy bills by 60–80%
Often installed with gas/electric boosters

These systems don’t just stop the leaking drama, they’ll make your energy bills look friendlier too.

Common Mistakes Homeowners Make

Even the handiest DIYers can slip up when dealing with a hot water system leak. Watch out for these traps:

Ignoring “small” drips that grow over time.

Switching power back on before refilling the tank (can fry heating elements).

Over-tightening valves or fittings.

Forgetting to check rebate eligibility before upgrading.

Skipping yearly maintenance is the silent killer of water heaters.

Don’t Let a Leak Dampen Your Day!

A hot water system leaking isn’t just about wasted water: It’s about stress, rising bills, and a wet floor you didn’t ask for. But here’s the good news: most leaks are simple, fixable, and preventable with a bit of know-how.

So next time you hear that tell-tale drip, don’t panic. Grab your wrench, shut off the power, and play detective. Whether it’s a loose valve or a tank ready for retirement, you now know what to do and when to call the experts.

Because in the end, every Aussie deserves hot water without the drama, and a bathroom floor that stays dry.

Frequently Asked Questions (FAQs)

Why does my hot water system leak only when I’m using hot water?

This usually happens when the water expands as it heats up, increasing internal pressure. If your system doesn’t have an expansion tank or the pressure relief valve is worn out, that pressure escapes as a leak. Installing a new valve or expansion tank can solve this quickly.

My hot water system is leaking from the overflow pipe. Is that bad?

A small trickle during heating is normal; it means your pressure valve is working correctly. But if water flows constantly, that valve is likely stuck or faulty. It’s a cheap part to replace but should be fixed fast to prevent energy waste and water damage.

Can a leaking hot water system increase my electricity or gas bills?

Yes, and often by more than you’d expect. Even slow leaks make your system work harder to maintain water temperature, which means it’s reheating more often. That constant energy use adds up quickly on your bill.

Is it safe to use hot water while my system is leaking?

Not recommended. Using hot water adds more pressure to the system and could worsen the leak. For safety, switch off both the power (or gas) and the water supply, then investigate the cause or call a plumber.

What causes a brand-new hot water system to start leaking?

Most times, it’s due to poor installation or loose fittings. Sometimes, new systems drip slightly as the valves settle, that’s normal for a few hours. But continuous dripping or pooling water means something isn’t sealed correctly and should be checked immediately.

Can I temporarily stop a hot water system leak myself?

If the leak is from a fitting or valve, you can shut off the cold-water supply and gently tighten the connection. Avoid using tape or sealant on the tank itself, those fixes don’t last under heat or pressure. For major leaks, always get a professional.

How can I prevent my hot water system from leaking in the future?

Regular maintenance is the secret. Check for rust or moisture every few months, flush out sediment once a year, test your pressure valve, and replace your anode rod every 2–3 years. A little upkeep goes a long way toward avoiding costly leaks and early replacements.

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