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Should I Turn Off My Hot Water When on Holiday? An Honest Plumber's Answer
Should I Turn Off My Hot Water When on Holiday? An Honest Plumber's Answer, a Prime Plumbing & Gasfitting plain-English guide to should i turn off my hot water when on holiday for Melbourne homeowners. Below we cover what works, what doesn't, and when to call a licensed plumber.
Quick answerFor trips over a week, turning OFF gas storage (or switching electric storage to "Vacation" / lowest setting) saves a small amount and is fine, but flush the unit thoroughly when you return before drinking the hot water. Continuous-flow units only run when you use water, so there's no benefit to turning them off. Heat pumps usually have a "Vacation" mode that's the right answer for trips of any length.
This is one of those questions where the answer depends on the system type AND how long you're away. Here's the practical breakdown.
By system type
Gas storage (Rinnai, Rheem, Vulcan, Bosch storage)
Trips under a week: leave it on.
Trips 1-3 weeks: optional, turning OFF saves maybe a few dollars on the gas bill. If you choose to turn off, flush thoroughly on return (run hot water for 5+ minutes at every outlet before using).
Trips 3+ weeks: turn off. You're getting actual savings AND avoiding running a hot tank you're not using. Same flush-on-return advice.
How to turn off a gas storage unit:
- Turn the gas control knob to OFF (NOT to PILOT, full off)
- Optionally close the gas isolation valve at the unit (small lever on the gas line)
- Optionally close the cold water isolation valve (lets the tank stay full but doesn't refill if there's a leak)
On return: turn the gas back to ON, follow the relight instructions on the unit's label, give the tank 30-60 minutes to come up to temperature, then flush hot water at every outlet for 5+ minutes before drinking or using for cooking.
Electric storage (Rheem Stellar, Rinnai HotFlo, Aquamax, Dux Proflo)
All trip lengths: switch to "Vacation" or "Holiday" mode if your unit has it (most modern units do, usually labelled on the controller).
If your unit doesn't have a vacation mode, the tariff matters:
- Off-peak (continuous tariff): leave on. Savings from turning off are minimal because you're paying off-peak rates anyway.
- Off-peak (overnight only): leave on for trips under a week. For longer, optionally switch off at the dedicated circuit breaker.
- Standard tariff (full-time on): turning off for trips of 1+ weeks saves real money on the electricity bill.
Important: don't turn off an electric storage unit at the isolation valve (water side), turn it off at the circuit breaker (electrical side). Leaving water in the tank is fine; leaving the heater running on an empty tank is not.
Continuous-flow gas (Rinnai Infinity, Rheem Metro, Bosch Highflow)
All trip lengths: leave it on. Continuous-flow units only consume gas WHEN water is flowing through them. With nobody home, water isn't flowing, so the unit isn't using gas (beyond a tiny pilot or electronic standby). Turning off just creates the inconvenience of relighting when you return, with effectively zero savings.
The exception: if you're concerned about a leak developing while away (legitimate concern on older units), close the cold water isolation valve and the gas isolation valve as a safety precaution. The unit doesn't need a "shut down", you're just isolating it from supply.
Heat pumps (Sanden, iStore, Reclaim Energy, Stiebel Eltron)
All trip lengths: switch to "Vacation" mode on the controller. Most modern heat pumps have this, it suspends scheduled heating cycles while keeping the tank at a low standby temperature.
For older heat pumps without vacation mode, leaving on is generally fine for trips under 2 weeks (heat pumps run efficiently and standby cost is low). For longer trips, switching off at the circuit breaker is OK, flush on return.
Solar hot water (panels + tank)
Don't turn off solar, even when you're not using hot water, the panels are designed to circulate water through the tank to prevent the panels themselves from overheating. Disabling the system can damage the panels in summer. Most solar systems have a "Holiday" mode on the controller that handles this correctly.
The legionella concern (why "off + flush" matters)
When hot water sits in a tank below ~50°C for days, Legionella bacteria can multiply. Australian regulation already requires tempering valves to limit OUTLET temperature to 50°C max, but the TANK should run at 60°C+ to keep bacteria suppressed.
If you turn the heater off entirely, the tank cools to ambient over a few days.
The fix is simple: when you return, run hot water for 5+ minutes at every outlet (especially showers) BEFORE breathing in the steam or using it for cooking/drinking. Five minutes of hot flush flushes the lines and brings the tank above 60°C.
The longer the off period, the more important the flush.
What about turning off the water entirely?
A different question. Some homeowners shut off the mains water valve at the meter before holidays, protects against burst pipes or appliance leaks while away.
This is a separate decision and applies regardless of hot water unit type. If you do shut off mains:
- Drain the toilet cisterns slightly (don't flush them dry, just drop the level a little) so any leftover pressure isn't held in the supply line
- Turn off the hot water heater first (so it doesn't run dry if there's any draw)
- Open one tap inside the house briefly to relieve pressure in the line
Worth doing for trips of 2+ weeks, especially in older homes where supply line failures are more likely.
What about the hot water unit's pilot? (gas storage only)
If you turn off a gas storage unit, the pilot also goes out. That's expected behaviour. On return, you relight the pilot following the instructions on the unit label.
If you're worried about whether YOU can relight it, leave a relit unit running while you're away, the cost is small. Or have someone (housesitter, neighbour with a key) check on it.
Book a service
Hot water issue or pre-holiday assessment? Call 0475 407 670 or send the make + model of your unit through the contact form.
- BPC #103414: Plumbing Industry Commission licensed
- Type A Gasfitter: registered with Energy Safe Victoria
- 4.8 stars on Google
- Fixed-price written quote before any work
- Certificate of Compliance lodged with ESV on gas work
Related: How long does a hot water system last? · Is it dangerous if the pilot light goes out? · Hot Water Systems Melbourne · Hot Water Replacement Melbourne
About the author
Alister Williams is the founder and lead plumber of Prime Plumbing & Gasfitting. He's been licensed under BPC #103414 for over a decade, holds Type A Gasfitter endorsement with Energy Safe Victoria, and is a member of the Master Plumbers Association of Victoria.
When to call us
Book a hot water service visit if:
- You don't know how old your unit is (we can decode the data plate and tell you)
- You're concerned about leaks while away on long trips
- You want to discuss replacing an aging unit before going overseas
- You've returned from a trip and the unit isn't relighting / restarting properly
Service area
Prime Plumbing & Gasfitting services hot water issues across Melbourne's eastern, south-eastern, inner-east and bayside suburbs. See all suburbs we service
When to Call a Licensed Plumber
Some plumbing problems are DIY-friendly; others need a licensed professional under Victorian law.
Anything involving gas, sewer drainage, hot water units, backflow prevention, or work behind tiled walls must be handled by a licensed plumber or gasfitter.
Frequently asked questions
Not directly. Leaks happen because of pre-existing wear, not because the unit is on. But IF a leak develops while you're away on a unit that's running, water will keep flowing, and that becomes a much bigger problem than a leak you discover after a 2-day weekend. For trips of 2+ weeks, isolating the cold water inlet to the hot water unit (or shutting off mains entirely) is reasonable insurance.
Yes, and this is sometimes a better option than full-off. Drop the thermostat to "low" or "vacation" setting (usually 50-55°C).On gas storage and electric storage, this works. On continuous-flow there's no equivalent (the unit only fires when you use water).
You CAN close that, but it's a bigger commitment, you'll need to relight every gas appliance (hot water, oven, gas heater) on return. For trips of 4+ weeks where you're concerned about gas leaks while away, it's worth doing. For shorter trips, the unit-level isolation valve is enough.
Yes if you can isolate the irrigation separately. Turning off mains entirely will also disable irrigation, your garden suffers. Most properties have an irrigation isolation valve that lets you keep irrigation running while shutting off house supply.
Run hot water for 5 minutes at every outlet before using normally. The flush retroactively suffices.
Some modern systems (heat pumps especially) have phone apps that let you switch to vacation mode remotely. For older units, a simple switch on the circuit breaker (electric) or the gas control (gas) is the only option.
Before You Book
A quick checklist to share with your plumber when you book:
- When did the issue start?
- Is it isolated to one fixture or multiple areas?
- Are there any visible leaks, smells or unusual sounds?
- Have you turned off the relevant isolation valve?
If you're unsure, Prime Plumbing & Gasfitting can inspect the issue and explain the options before any work starts. Call 0475 407 670 or request a quote online.
