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A puddle of water around your hot water unit is never something to ignore. As a leading plumber Sydney homeowners call for urgent hot water issues, Hero Plumbing attends leaking hot water system callouts across Sydney every day. This guide explains the most common reasons a gas hot water system leaks, what risks a leak creates, and what your repair and replacement options are.
Why is my gas hot water system leaking?
A leak from a gas hot water system can originate from several different components, and the source matters enormously when deciding whether to repair or replace:
Pressure relief valve (PRV) leaking
The temperature and pressure relief valve (TPR valve) is a safety device that releases excess pressure to prevent the tank from bursting. A small amount of discharge from this valve during heating cycles is normal. However, a valve that is constantly dripping or running means one of two things: the valve itself is faulty and needs replacing (a relatively affordable repair), or your system’s pressure is consistently too high, indicating a problem with the pressure reducing valve or thermostat.
Tank corrosion and internal rusting
The most serious cause of a leaking gas storage tank is internal corrosion. When the sacrificial anode rod (which protects the tank lining) is depleted, the steel tank begins to corrode from the inside. Once the tank wall is compromised, water seeps through and the tank cannot be repaired. Replacement is the only option.
Loose or corroded fittings and connections
The inlet and outlet pipe connections at the top of the tank can loosen or corrode over time. In many cases, a dripping connection can be tightened or resealed by a licensed plumber without requiring full system replacement.
Drain valve dripping
The drain valve at the base of the tank is used for flushing sediment. Drain valves can develop leaks from deterioration or after being operated. A leaking drain valve can usually be replaced without a full unit replacement.
Heat trap fittings
Heat traps on the inlet and outlet connections prevent heat loss by convection. These can corrode or fail, causing drips at the top of the tank. Replacement of heat traps is a straightforward repair.
Can a leaking gas hot water system cause a gas leak?
Water itself does not cause a gas leak, but water damage around gas connections, valves, or the gas supply line to the unit can accelerate corrosion and eventually compromise gas fittings. If you notice a rotten-egg smell in addition to water near your hot water system, treat this as a gas leak situation. Turn off the gas at the meter, ventilate the area, and call a licensed gas fitter immediately. Do not use any electrical switches or your phone indoors until you are in the open air.
Is a leaking gas hot water system dangerous?
Yes, for multiple reasons. Water damage from a slow leak can cause structural damage to floors, walls, and subfloors over time, particularly in indoor laundry areas. More critically, a tank under pressure that is failing structurally is a genuine burst risk. A burst hot water tank can cause serious damage to the property and risk injury. If you see signs of tank corrosion or the leak is coming from the tank body itself, call a plumber immediately.
What should I do if my gas hot water system is leaking?
- Turn off the cold water supply to the hot water unit (usually a valve on the cold water pipe feeding into the top of the unit).
- If you smell gas, also turn off the gas at the meter and leave the area immediately.
- Call Hero Plumbing for an urgent assessment.
Repair vs replacement: what to expect
A licensed plumber will diagnose the source of the leak and advise on the most cost-effective path forward:
- PRV replacement, drain valve, or connection repair: Relatively affordable; no need to replace the whole system.
- Tank corrosion / tank body leak: Replacement is the only option. A corroded tank will continue to fail regardless of patches.
- System over 10 years old with any leak: In many cases, the cost-benefit of repair versus replacement favours a new unit.
Read our full guide on whether to repair or replace your water heater and why you have no hot water for additional context.
Book an urgent hot water assessment in Sydney
A leaking gas hot water system is a high-priority callout. Hero Plumbing carries out same-day hot water assessments and replacements across all Sydney suburbs. We carry stock of all major brands for immediate installation when replacement is needed. Call us now or book online.
Frequently Asked Questions
Can a gas water heater leak gas?
The water itself does not cause a gas leak, but water damage around gas fittings can accelerate corrosion and eventually compromise gas connections. If you smell gas near your leaking hot water system, treat it as a gas emergency and call a licensed gas fitter immediately.
What causes a gas hot water system to leak?
The most common causes are a faulty pressure relief valve, internal tank corrosion, loose or corroded pipe connections, a dripping drain valve, or failed heat trap fittings.
Is it safe to use a leaking gas hot water system?
No. A leaking tank indicates a structural or component failure. Using a system with a corroded or compromised tank is a risk. Turn off the water supply and call a plumber promptly.
Can a leaking hot water system be repaired?
Depending on the source of the leak. Minor component leaks (valve, fittings, drain valve) can usually be repaired. A corroded tank body cannot be repaired and must be replaced.
How much does it cost to fix a leaking gas hot water system in Sydney?
Minor repairs vary in cost depending on the component. Full replacement costs vary by system type and size. Hero Plumbing provides upfront pricing before any work begins.
