# Hot Water Leaking from the Bottom? Do This Now > Hot water leaking from the bottom? Isolate the water and power now - what a base leak vs valve leak means and when to call an emergency plumber. URL: https://perthhotwatersystem.com.au/guide/hot-water-leaking-from-bottom/ Last-Modified: 2026-08-10 Guides — Explainer # Hot Water System Leaking from the Bottom? Water under your hot water tank? Isolate the supply and power first. What a base leak means versus a valve leak, and when to call an emergency plumber. Published 10 August 2026 · 4 min read ![Water pooling under a hot water tank at a Perth home](/images/featured/water-pooling-on-the-concrete-underneath-a-hot-wat.webp) ## Do these three things first If there is water under your hot water system right now, deal with the immediate situation before reading anything else. **1\. Close the cold water isolation valve.** It is on the pipe entering the top of the unit, usually a small lever or a screw-type tap. Turning it off stops the tank refilling from the mains, which stops the leak feeding itself. This is the single most useful thing you can do. **2\. Isolate the power or gas.** For an electric system, switch off the breaker labelled hot water, HWS or water heater at your switchboard. For a gas system, close the gas isolation valve at the unit. This stops the system trying to heat a tank that is emptying. **3\. Keep clear of the water.** Water leaving a failed hot water system can still be scalding an hour or more after the power is off. Do not walk through it barefoot and keep children and pets away. Then call. Our emergency hot water repairs [/emergency-hot-water-repairs/ →](/emergency-hot-water-repairs/) team runs 24/7 across the Perth metro, and an active leak is exactly the kind of job we prioritise. ![Hand turning off the cold water isolation valve above a hot water unit](/images/content/hand-turning-off-the-cold-water-isolation-valve-on.webp) ## Where the leak is decides everything This is the distinction that determines whether you are facing a modest repair or a replacement, and it is worth understanding before anyone gives you a price. | Leak location | What it means | Likely outcome | | --- | --- | --- | | Pressure temperature relief valve | Valve failing or normal discharge | Repair, valve replacement | | Tempering valve | Seal or valve failure | Repair | | Flexible connection or fitting | Perished seal or loose fitting | Repair, inexpensive | | Cold or hot water pipe joint | Corroded or loose joint | Repair | | Base seam of the cylinder | Tank corroded through internally | Replacement, no repair possible | A drip from a valve or a fitting is a normal maintenance item. Fixing it is quick and cheap. A leak from the base of the cylinder itself is different. It means the steel tank has corroded from the inside out, usually because the sacrificial anode rod was consumed years ago and nobody replaced it. There is no repair for that. Welding or patching a corroded cylinder wall does not work, because the entire tank has thinned and the next weakest point simply goes instead. ## Why it worsens rather than stabilises A pinhole in a corroded cylinder does not stay a pinhole. The tank is under mains pressure, the metal around the failure is already thin, and the leak enlarges the opening. A slow weep on Friday can be a substantial flow by Sunday. That is why we treat base leaks as urgent rather than “book it for next week”. The damage cost of water running through a side passage, under a wall or across a garage floor for three days regularly exceeds the cost of the replacement itself. ## The one exception: normal PTR discharge Not all water under a hot water system is a fault. The pressure temperature relief valve is designed to discharge periodically as water expands during heating. A small amount of water coming out of the PTR drain line, particularly during or shortly after a heating cycle, is the valve doing its job. What is not normal is a continuous stream, discharge that never stops, or a valve that discharges heavily. That points to excessive mains pressure, a failed valve, or a thermostat running too hot. Any of those needs a plumber, but it is a repair rather than a replacement. ## What happens when we arrive We identify the leak source first, because everything follows from that. If it is a valve or fitting, we repair it on the spot from stock on the truck. If the cylinder has failed, we tell you straight, and quote a replacement rather than pretending a repair is possible. Where the system needs replacing and stock allows, we can often complete a same-day changeover across the Perth metro. Where the specific unit needs ordering, we can usually arrange a temporary hot water solution so the household is not left without. If your tank has failed outright rather than developed a slow leak, our guide on the immediate steps for a burst tank [/guide/burst-hot-water-tank-what-to-do/ →](/guide/burst-hot-water-tank-what-to-do/) covers damage control while you wait. FAQ ## Common questions ### Is a hot water tank leak an emergency? expand\_more A leak from the base of the cylinder is, yes. It does not stabilise, it worsens, and the tank keeps refilling from the mains and feeding the leak. Isolate the cold water supply and the power or gas, then call for 24/7 dispatch. ### Can a leaking hot water tank be repaired? expand\_more Valve and fitting leaks very often can. A leak from the base seam of the cylinder cannot, because the steel has corroded through from the inside and patching one spot simply moves the failure to the next thinnest point. ### What should I turn off first? expand\_more The cold water isolation valve on the pipe entering the top of the unit, which stops the tank refilling. Then the power at the circuit breaker for an electric system, or the gas isolation valve for a gas one. ### Still have a question? Talk to a licensed Perth plumber. No call-out surprises, no obligation. Get a Free Quote [/contact/ →](/contact/) Call 08 6243 6734 [tel:+61862436734 →](tel:+61862436734) Next step ## Learn more about 24/7 Emergency Hot Water Repairs If this guide answered your question and you'd like a hand from a licensed Perth plumber, we'll take a look and quote it up front. No obligation. View Emergency Repairs [/emergency-hot-water-repairs/ →](/emergency-hot-water-repairs/) Browse all guides [/guide/ →](/guide/)