Leaking Hot Water System: Is It an Emergency?

Updated July 2026 · 7 min read · Geelong Emergency Plumbing

A puddle under the hot water system triggers a very specific dread — that unit was expensive, it's probably old, and it's currently holding up to 400 litres of scalding water above your puddle. The good news: not every leak is a crisis, and one of the most common "leaks" is actually the system working correctly. Here's how to tell the difference, what to do right now, and when the puddle is a replacement notice.

First: Find Where It's Coming From

Grab a torch and look before you panic. The source determines everything:

• A small pipe near the top or side, dripping occasionally — that's the temperature/pressure relief (TPR) valve, and occasional dripping during heating cycles is normal operation. It's literally the valve's job to release expansion. No dripping ever is actually more suspicious than some.
• The TPR valve running constantly — a steady stream rather than heat-cycle drips means the valve has failed or system pressure is too high. Not an emergency, but book it promptly; it's a small repair, and it's also your safety valve, so it needs to work.
• Fittings and connections — leaks at the cold inlet, hot outlet or valves are usually seals and unions: repairable, routine, cheap-ish.
• The tank body itself — water weeping from seams, under the casing, or pooling with no valve involvement means the cylinder has corroded through from the inside. This is the one with no repair: tanks are not patchable, and a weeping tank only ever gets worse, occasionally dramatically.

Is It an Emergency? The Honest Scale

Call now: water flowing (not dripping), any bulging of the tank, hot water spraying from a fitting, water reaching electrical components, or a leak you can't slow with the steps below. A split tank can release its entire contents quickly, and it releases them hot.

Same-day but not sirens: steady TPR stream, tank weeping slowly, active drips at fittings. Isolate (below), catch the water, book today.

Book normally: occasional TPR drips during heating — that's Tuesday for a hot water system. Mention it at your next service.

Shut It Down Safely (Three Valves, Two Minutes)

1. Cold water inlet off. The valve on the cold pipe entering the unit — turn clockwise. This stops the tank refilling and feeding the leak. (Can't find it or it's seized? The mains valve does the whole-house version.)
2. Energy off. Electric: switch off the hot water breaker at the switchboard — a leaking tank with a live element that ends up exposed is how elements burn out and worse. Gas: turn the gas control to OFF, and the gas isolation valve if accessible.
3. Relieve pressure gently. Open a hot tap indoors briefly. Don't drain the tank yourself — 300 litres of hot water needs somewhere sensible to go, and the plumber has that handled.

Then contain the water away from anything electrical, and if the unit lives in a cupboard or roof space, move what's underneath — water travels, as anyone who's read our burst pipe guide can testify.

Repair or Replace? Read the Leak

Valves, seals and fittings: repair — typically $150–$400 and done in a visit. Tank body: replace — no exceptions, because corrosion through the cylinder wall means the glass lining and sacrificial anode did their years and lost. The average storage tank lasts 8–12 years; if yours is leaking from the body inside that window, check your warranty (cylinders often carry 5–10 year warranties), and if it's beyond it, the money conversation is in our replacement cost guide — including why a failure day is actually a decent day to consider the heat pump upgrade while rebates are on the table.

The Insurance Angle

Sudden tank failures that damage flooring or walls are commonly claimable as sudden escape of liquid; slow weeping that stained a cupboard over months usually is not (gradual damage exclusions again). Photograph everything before cleanup and get the plumber's written note on the cause — the full playbook is in our insurance guide.

Prevention for the Next Unit

Two habits double as lifespan insurance: have the sacrificial anode checked around year 5 (a rod that corrodes so your tank doesn't — replacing it can add years), and give the TPR valve a brief manual lift-test annually per its tag. Also: don't box the unit in — a drip tray with a drain line and visible clearance means the next leak announces itself politely instead of through the ceiling.

One Last Check: Where Does the Water Go?

While the plumber is there, ask one future-proofing question: does the unit sit in a drip tray with a drained overflow line? Older installs often don't, and indoor or roof-space units without safe-tray drainage are the ones that turn a slow weep into a ceiling repaint. Adding a compliant tray and drain line during a valve repair costs little; retrofitting it after a flood costs a story you'll tell for years. It's the plumbing equivalent of a smoke alarm — invisible until the exact moment it saves you thousands.

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Related guides: Hot water system cost guide · No hot water troubleshooting · Hot water repairs Geelong