Gas hot water covers installing, replacing and repairing water heaters that burn gas. There are two main types: continuous-flow units, which heat water only when a tap opens, and storage tanks, which keep a volume of water hot. Across Mackay these systems almost always run on LPG from cylinders or a bulk tank. Replacing one involves gas work and plumbing work, so it is worth knowing which licences and paperwork apply before you request a connection with a local provider.
Continuous flow or storage: the basic decision
| Factor | Continuous flow (instantaneous) | Gas storage tank |
|---|---|---|
| How it heats | Burner fires when hot water is drawn | Burner keeps a tank of water at temperature |
| Hot water supply | Does not run out while gas is available | Limited by tank size and recovery rate |
| Gas demand | High peak demand when running | Lower, steadier demand |
| Space | Compact, wall-mounted | Needs floor space for the tank |
| Common Mackay issue | Cylinders or regulator undersized for peak demand | Tank corrosion and relief valve problems over time |
| Power | Usually needs a power point for controls | Some models need no mains power |
Neither type is best for every home. Household size, how many showers run at once, where the unit sits and your existing gas supply all affect the choice. A continuous-flow unit pulls a lot of gas while it runs, and small cylinders cannot always vaporise LPG fast enough. That is why the supply check matters.
When to call about gas hot water
- No hot water at all. Check that the gas cylinders are not empty and that the unit has power, if it needs it. If both are fine, the fault needs diagnosis.
- Lukewarm or fluctuating water. On continuous-flow units this can come from a gas supply that cannot keep up, a flow problem, or a component fault.
- Error codes. Many continuous-flow units display fault codes. The manual explains what some of them mean, but repairs to gas components are gas work.
- Leaking tank or relief valve. A storage tank leaking from the base is usually near the end of its life. Constant dripping from the relief valve should also be checked.
- Replacement planning. If a unit is old, a planned replacement is generally less stressful than an emergency one.
Two sets of rules apply
Gas water heater replacement in Queensland usually involves two separate pieces of compliance.
- Gas work. The gas connection, testing and commissioning must be done by a licensed gasfitter, who issues a gas system compliance certificate to the owner when an installation or alteration is finished. See gas compliance certificates.
- Plumbing work. The QBCC lists installing or replacing water heaters, including gas units, as notifiable plumbing work. The licensed plumber must register it with the QBCC rather than getting a council permit.
Many providers hold both licences, so one visit can cover both. Still, check that the person doing the gas side holds a current gas work licence.
What a replacement usually involves
- Assessment. The provider confirms the existing system type, location, gas supply and water connections, and talks through whether to replace like for like or change type.
- Supply check. Before adding or increasing gas demand, the gasfitter has to make sure the supply is enough. With LPG, that includes cylinder storage and vaporisation rate, plus pipe sizing.
- Removal. The old unit is isolated, drained if it is a tank, and disconnected.
- Installation. The new unit is mounted or placed with the required clearances, flue position and water connections, including valves required under plumbing rules.
- Commissioning. Gas pressure and burner operation are checked, the water temperature is set, and the system is leak tested.
- Paperwork. You receive the gas compliance certificate, and the plumbing work is registered as notifiable work.
Mackay considerations
- LPG supply sizing. Switching from a storage tank to continuous flow can push an older cylinder setup past its limits. A regulator or cylinder change may be part of the job; see LPG gas bottle connection.
- Outdoor units and the weather. Most units in the region are mounted outside. Salt air near the coast and heavy wet-season rain can shorten the life of exposed parts, so choose a model rated for outdoor use and leave access for servicing.
- Storm season. If a storm damages a unit, or flooding reaches it, do not use it until it has been checked.
- Water quality. Local water conditions affect tank life and valve wear. Ask your provider what maintenance suits your system.
Maintenance that helps
Manufacturers generally recommend periodic servicing by a qualified person. Check your manual for the schedule. Between services, homeowners can:
- keep the area around the unit clear of plants, rubbish and stored items;
- watch for scorching, soot or an unusual flame;
- notice changes in water temperature or pressure;
- operate the relief valve easing lever only if the manual says to, and stop if water keeps flowing afterwards.
Frequently asked questions
Should I replace my gas storage tank with continuous flow?
It depends on how much hot water your household uses, your gas supply and the installation position. Continuous flow avoids running out of hot water but needs a higher gas flow rate, which may mean upgrading cylinders or the regulator on an LPG property.
Why does my continuous-flow hot water go cold when two showers run?
Common causes include a unit that is too small for the demand, a gas supply that cannot deliver enough gas at peak, or a water pressure or flow issue. A gasfitter can measure the gas pressure while the unit is running to narrow it down.
Can one tradesperson handle both the gas and plumbing for a hot water swap?
Often yes, if they hold both a plumbing licence and a gas work licence. Confirm this before booking, because the gas certificate and the plumbing notification are separate requirements.
Is a leaking gas hot water tank dangerous?
A water leak from the tank is usually a sign the tank is failing, not a gas emergency. Still, isolate the water if you can and arrange an inspection. If you smell gas near the unit, treat it as a possible gas leak.
How long does a gas hot water replacement take?
A like-for-like swap is usually done in a single visit. Changing system type, relocating the unit or upgrading the gas supply adds time. Ask the provider for an estimate when they quote.
Related services
- Gas leak detection if you smell gas near the water heater.
- Gas appliance servicing and repairs for other gas appliances.
Request a connection with a local provider
This site is a referral service and does not install or repair water heaters. Describe your current system, the problem and your gas supply, and we will forward your enquiry to a local Mackay provider to confirm licensing, options and price with you directly.