Water Heater Safety Check
Assess Your Water Heater Risk
Answer these questions to determine if your water heater needs professional attention.
It’s 5 a.m. and your shower is ice cold. You’ve checked the thermostat, flipped the circuit breaker, and even yelled at the tank like it’s a stubborn teenager. Now you’re wondering: should you fix your own water heater? The internet says yes. Your neighbor says yes. But your gut says no. And for good reason.
Most water heater fixes aren’t worth the risk
Water heaters are not like changing a lightbulb or unclogging a drain. They combine high-pressure water, scalding temperatures, and potentially explosive gas or electrical systems-all in one metal tank under your house. In New Zealand, where plumbing codes are strict and water pressure is often higher than in other countries, DIY fixes can turn into costly disasters fast.
Take the most common fix people try: replacing the heating element. Sounds simple, right? You turn off the power, drain the tank, unscrew the old one, and plug in the new. But here’s what no YouTube video tells you: if you don’t flush the tank first, mineral buildup can clog the new element in weeks. If you don’t use the right torque on the fittings, you’ll crack the porcelain coating and cause a slow leak that eats away at your floor. And if you forget to turn off the gas line before working on a gas model? That’s not a repair. That’s a waiting game for the fire department.
According to WorkSafe New Zealand, over 120 residential water heater incidents were reported in 2024 alone-nearly 40% of them linked to amateur repairs. Most involved burns, gas leaks, or electrical shorts. None of them were worth saving $200 on a plumber’s bill.
When DIY might actually work
Not all water heater problems need a professional. There are two things you can safely check yourself: the thermostat and the pressure relief valve.
The thermostat is easy. If your water is lukewarm but the heater is running, turn the dial up 5 degrees and wait an hour. If nothing changes, the thermostat might be faulty. But don’t replace it yet. First, test the power. Use a multimeter to check if 240 volts is reaching the unit. If it’s not, the issue could be a tripped breaker or a bad circuit. Fix that, and you’re done.
The pressure relief valve is another low-risk check. This valve opens automatically if pressure gets too high. Every six months, lift the lever on the valve to make sure water flows out. If it doesn’t, or if it drips constantly after you let go, it’s clogged or worn. Replacing it costs under $30 and takes 20 minutes. Just turn off the water and power, drain a few liters from the tank, and swap it out. No special tools needed.
These are the only two fixes that won’t likely end in disaster. Everything else? Leave it to someone who’s done it 200 times.
What you’re really paying for
When you hire a plumber, you’re not just paying for their hands. You’re paying for their experience, their tools, and their insurance.
Professional plumbers carry liability insurance. If they crack your tank during repair, they pay to replace it. If they accidentally flood your house, their insurance covers the damage. You? You’re on the hook. A single leak from a bad repair can cost $10,000 in water damage, mold remediation, and flooring replacement.
They also know the code. In Auckland, water heaters must be installed with a temperature and pressure (T&P) valve within 150mm of the top of the tank, with a discharge pipe running directly to the floor. Most DIYers don’t know this. A plumber does. And if your system fails inspection during a home sale, you’ll have to fix it anyway-at your cost.
Plus, pros have access to wholesale parts and diagnostic tools you can’t buy at Bunnings. They can tell if your anode rod is half-gone by looking at the water’s smell. They know which brands have recurring faults in NZ’s hard water areas. That kind of insight saves you money over time.
The hidden dangers you won’t see
Here’s what most people don’t realize: water heaters don’t just break. They fail silently.
A rusted tank might not leak for months. But when it does, it’s not a drip. It’s a geyser. The average tank holds 120-200 liters of water under pressure. One crack and you’re looking at a flood that can destroy drywall, flooring, and even the structure of your home.
Gas heaters have another silent killer: carbon monoxide. A cracked heat exchanger or blocked flue can leak this odorless, colorless gas into your home. Symptoms? Headaches, dizziness, nausea. In severe cases, death. A professional uses a gas leak detector and CO monitor. You? You’re guessing.
And then there’s the electrical side. Water heaters draw 30-50 amps. If your wiring is old, or if you use the wrong gauge wire during a DIY fix, you’re creating a fire hazard. In 2023, a study by the New Zealand Electrical Safety Authority found that 27% of home electrical fires linked to appliances started with improper water heater repairs.
Signs you need a pro-right now
Don’t wait until your bathroom looks like a swimming pool. Here’s when to call someone immediately:
- Water is rusty or smells like rotten eggs (sulfur bacteria or corroded anode rod)
- You hear banging, popping, or rumbling from the tank (sediment buildup)
- The pilot light won’t stay lit on a gas model
- Water is leaking from the bottom of the tank (tank failure)
- The heater is over 10 years old and showing any signs of trouble
If you see any of these, don’t try to fix it. Turn off the power and water supply, then call a licensed plumber. Delaying increases the risk-and the cost.
What a real repair looks like
When a plumber comes to fix your water heater, here’s what they actually do:
- Shut off the gas or electricity
- Drain the tank using a hose connected to the outlet valve
- Check the anode rod for corrosion
- Test the thermostat, heating elements, and pressure relief valve
- Flush the tank to remove sediment
- Replace faulty parts with manufacturer-approved components
- Reconnect and pressure-test all fittings
- Check for gas leaks or electrical faults
- Set the temperature to 60°C (the NZ safety standard)
- Document the work and provide a warranty
They don’t just swap parts. They diagnose the whole system. And they leave you with a certificate that says it’s safe and compliant.
When replacement beats repair
Most water heaters last 8-12 years. If yours is older than 10 and you’re spending more than $300 on repairs, it’s time to replace it.
New models are 20-30% more efficient. They come with better warranties. And many now have smart features-like leak detection and remote temperature control. A good electric heat pump water heater in Auckland can cut your energy bill by half.
Plus, some councils offer rebates for upgrading to energy-efficient models. Check with your local council. You might get $500 off.
Don’t fix an old heater just to delay the inevitable. Replace it right, and you’ll save more than you spend.
Final call: DIY or pro?
Here’s the truth: you can fix two things on your water heater safely. The thermostat and the pressure valve. That’s it.
Everything else-replacing elements, fixing gas lines, dealing with leaks, troubleshooting electrical faults-requires training, tools, and insurance you don’t have. The risk isn’t worth the savings.
Water heater failure doesn’t give you a warning. It just happens. And when it does, you don’t want to be the person who tried to save $200 and ended up paying $10,000.
Call a licensed plumber. It’s not expensive. It’s not scary. It’s just the smart thing to do.
