Hot Water System Leaking
Hot Water Repairs
Hot Water System Leaking?
Here’s What To Do.
You walk out to the laundry or backyard and there’s a puddle under your hot water unit. Or you notice a damp patch on the wall nearby. Either way, a leaking hot water system isn’t something you ignore and hope it fixes itself.
The good news: not every leak means you need a new system. The bad news: some of them do, and the longer you leave it, the worse it gets. This guide walks you through why it’s leaking, what to do right now, and how to figure out whether you need a repair or a full replacement.
What to do right now
If you’ve just found the leak, follow these steps before anything else:
- Turn off the water supply to the unit. There’s an isolation valve on the cold water inlet pipe that feeds into the system. Turn it clockwise to shut it off.
- Turn off the gas or power supply. For gas systems, turn off the gas valve near the unit. For electric systems, switch off the circuit breaker for the hot water system in your switchboard.
- Don’t drain the tank yourself unless you’re confident with what you’re doing. A hot tank under pressure can cause burns.
- Call a licensed gas plumber Especially with gas hot water systems, do not attempt repairs yourself. Gas components require a licensed technician. Call The Gas Doctor on 0488 800 693.
Important
If you can smell gas near your hot water unit at any point, don’t touch any switches or appliances. Leave the property immediately and call your gas retailer or emergency services. Then call us.
6 common causes of a leaking hot water system
Most hot water system leaks trace back to one of these six causes. Some are minor fixes. Others mean it’s time for a new system.
Cause 01
Faulty TPR Valve
The temperature and pressure relief (TPR) valve is a safety device. If it’s leaking, it could be doing its job because the pressure inside is too high, or the valve itself may be worn out. Either way, it needs immediate attention.
Cause 02
Corroded or Cracked Tank
Over time, the inside of a storage tank corrodes. Once the tank itself is cracked or rusted through, the only fix is a full replacement. There’s no repairing a compromised tank.
Cause 03
Loose or Damaged Pipe Fittings
Inlet and outlet pipe connections can loosen over time or corrode at the joints. This type of leak is often repairable with a fitting replacement or re-seal without replacing the whole system.
Cause 04
Failed Anode Rod
The sacrificial anode rod prevents internal tank corrosion. When it degrades completely, the tank itself starts to corrode. Regular replacement of the anode rod is one of the best ways to extend the life of your system.
Cause 05
Inlet or Outlet Valve Failure
The cold water inlet valve and hot water outlet valve can both fail over time. A leaking valve at either point is usually a straightforward repair rather than a full replacement job.
Cause 06
High Water Pressure
If your incoming mains pressure is too high, it puts excess stress on valves, fittings, and the tank itself. A pressure limiting valve (PLV) can be installed to protect the system if this is the underlying problem.
Where is the leak coming from?
The location of the leak gives you a strong indication of the cause and whether it’s fixable or not.
Leaking from the top
A leak from the top of the unit usually points to the inlet or outlet fittings, the cold water inlet valve, or the connections on either side. These are generally repairable. Don’t mistake condensation on a cold pipe for an actual leak.
Leaking from the side
A leak from the TPR valve on the side of the tank is the most common cause of side leaks. A small amount of dripping from the TPR valve occasionally can be normal, but a steady or constant drip is not. It could indicate the valve itself is faulty, or that the water pressure inside the tank is dangerously high.
Leaking from the bottom
This is the most concerning location. A leak from the bottom often means the tank itself is corroded internally. Once water pools consistently at the base with no visible pipe or valve leak nearby, you’re likely looking at a tank replacement, not just a repair.
Quick check: if the water is only appearing occasionally and only after the system has been running, it may be condensation rather than a genuine leak. Touch the pipe nearest to the wet area. If the pipe is cold and the wet spot is directly beneath it, it’s likely condensation. A hot spot, discolouration, or water stain is a leak.
Should you repair or replace your hot water system?
This is the question everyone asks. The honest answer depends on the cause of the leak, the age of the system, and whether the damage is contained or widespread.
| Situation | Recommendation |
|---|---|
| Faulty TPR valve, valve is worn but tank is intact | Repair |
| Loose or corroded pipe fittings | Repair |
| Failed inlet or outlet valve | Repair |
| High water pressure (PLV needed) | Repair |
| Corroded or cracked tank | Replace |
| System is over 10 years old and leaking | Replace |
| Repeated breakdowns over the past 12 months | Replace |
| Internal tank fracture | Replace |
As a general rule, most storage gas hot water systems have a lifespan of 8 to 12 years with proper maintenance. If yours is approaching that range and it’s started leaking, putting money into repairs often doesn’t make financial sense. A new system is a more reliable long-term investment.
If your system is relatively new (under 5 years old) and the leak is from a fitting or valve, repair is almost always the right call.
Why you should never DIY a gas hot water system repair
We get it. A leaking system is stressful, and the temptation to Google the fix and sort it yourself is real. But gas hot water systems are not DIY territory.
In Victoria, gas work must be carried out by a licensed gas fitter. This isn’t just a legal requirement; it’s a safety one. Gas components under pressure, combined with heat and water, create genuine hazards if handled incorrectly. Mistakes can void your warranty, damage your property, and in serious cases, put lives at risk.
What you can do yourself is turn off the water and gas supply to the unit, as described in Step 1 above. Everything beyond that, leave it to a licensed professional.
The Gas Doctor operates 24/7 across Melbourne. Our vans carry common spare parts for most hot water brands including Rinnai, Rheem, Dux, Bosch, and Vulcan, so in most cases we can complete the repair in a single visit.
Frequently asked questions
Why is my hot water system leaking?
The most common causes include a faulty temperature and pressure relief (TPR) valve, a corroded or cracked tank, loose pipe fittings, a degraded anode rod, or a failed inlet/outlet valve. Where the leak is coming from gives you the first clue.
Is a leaking hot water system dangerous?
It can be. A leak left unaddressed can cause water damage, mould, and structural issues in your home. On a gas system, certain component failures can also indicate dangerous pressure build-up. Turn it off and call a licensed plumber promptly.
Can I use my hot water system while it’s leaking?
No. Turn off the water supply and gas or power supply to the unit and stop using it. Running a leaking system risks further damage, higher water bills, and potential safety hazards.
Should I repair or replace my leaking hot water system?
It depends on the cause and the system’s age. Minor leaks from valves or fittings are usually repairable. If the tank itself is corroded, or the system is over 10 years old and has had repeated issues, replacement is usually the smarter investment.
How long does a gas hot water system last?
A well-maintained storage gas hot water system typically lasts 8 to 12 years. Instantaneous (continuous flow) systems tend to last longer with regular servicing. If yours is approaching that range, factor in age when deciding whether to repair or replace.
How much does it cost to repair a leaking hot water system in Melbourne?
The cost depends on what needs to be done. Valve replacements and fitting repairs are generally straightforward and cost-effective. A full system replacement varies depending on the type and size of the unit. The Gas Doctor provides upfront pricing before any work begins, so you’ll know exactly what you’re up for.
Does The Gas Doctor service my area?
The Gas Doctor services Melbourne and surrounding suburbs 24/7. Check the areas page on the website or call 0488 800 693 to confirm.
Got a leaking hot water system? Don’t wait.
The longer you leave it, the worse it gets. The Gas Doctor is available 24/7 across Melbourne with fully stocked vans ready to repair or replace on the spot.
Call 0488 800 693Available 24/7 | Licensed Gas Fitters | All Major Brands Serviced