Understanding Your Caravan’s Hot Water System

Hot water in a caravan is one of those things you don’t think much about until it stops working, or until you’re standing in a campground shower block at 6am because your van’s system can’t deliver a warm shower. Understanding how your hot water system works, what type you have, and how to get the best out of it means you’ll spend more time enjoying hot showers in your own bathroom and less time troubleshooting temperamental heaters.

Most caravans sold in Australia come with one of three types of hot water system: gas, electric, or a combination of the two. Newer and premium vans are increasingly offering diesel options as well. Each has distinct advantages and trade-offs depending on how you travel, and this guide will help you understand what’s in your van, how to use it properly, and when an upgrade might be worth considering.

The Three Types of Caravan Hot Water Systems

Gas Hot Water Systems

Gas is the most common fuel source for caravan hot water in Australia. These systems run on LPG from your gas bottles, which makes them completely independent of mains power. That’s a significant advantage for free camping and off-grid travel. A gas burner heats water either in a storage tank or instantaneously as it flows through the unit, depending on the model.

The two big names are Truma (German-engineered, widely factory-fitted in Australian caravans) and Suburban (American-made, the workhorse of the Australian aftermarket). Truma’s UltraRapid is probably the most common factory-fitted unit you’ll encounter, while Suburban’s SW6D and SW6DE models are popular as both factory and aftermarket options. Gas systems typically heat a full tank in 30-45 minutes and use roughly 200-400 grams of LPG per heating cycle.

Electric Hot Water Systems

Electric systems use a 240V heating element to heat water in a storage tank. They’re simple, quiet, and have no open flame or gas connections to worry about. The downside is obvious: you need mains power. That means they only work when you’re plugged into a powered site at a caravan park or running a generator. For travellers who spend most of their time in caravan parks, electric-only systems are perfectly adequate. For anyone doing regular free camping, they’re a non-starter on their own.

Electric-only units are less common as factory-fitted options because of this limitation. The Suburban SW5EA is the most affordable option at around $500, with a generous tank capacity, and it’s popular with travellers who primarily stay at powered sites. Heating time is generally slower than gas, typically 40-60 minutes for a full tank depending on the element wattage and starting water temperature.

Diesel Hot Water Systems

Diesel hot water is the newest option in the caravan market and is gaining popularity quickly, especially in off-road and premium vans. These systems tap into a dedicated diesel tank (or in motorhomes, the vehicle’s fuel tank) and use a combustion process to heat water. The main players are Eberspacher (with their Hydroplate continuous flow system) and Autoterm.

The appeal of diesel for Big Lappers is straightforward: diesel is available everywhere in Australia, it’s generally cheaper per litre than LPG, and you don’t need to manage separate gas bottle refills. Diesel systems also pair neatly with diesel heaters for cabin heating, meaning one fuel source handles both space heating and hot water. The trade-off is higher upfront cost and the need for professional installation.

Combination (Gas/Electric) Systems

The most versatile option, and increasingly the default in new caravans, is a dual-fuel gas/electric system. These give you the best of both worlds: gas for off-grid camping, electric when you’re at a powered site. Running both simultaneously heats water faster than either fuel source alone. The Truma UltraRapid Gas/Electric heats a full 14-litre tank in about 28 minutes using both fuel sources together, compared to 45 minutes on gas alone or 40 minutes on electric alone.

Suburban’s combination models (like the SW6DE with its 22.6-litre tank) are a common sight in Australian caravans and offer the largest storage capacity in the category. The bigger tank means longer showers and the ability to supply hot water to multiple people without waiting for a reheat cycle.

Storage Tank vs Instantaneous: What’s the Difference?

Beyond the fuel source, caravan hot water systems fall into two categories based on how they heat water.

Storage Tank Systems

These heat a fixed volume of water (typically 10-23 litres) and store it in an insulated tank until you use it. When the tank empties, you wait for it to reheat. Most caravan hot water systems are storage type, including the Truma UltraRapid (14 litres), Suburban SW6DE (22.6 litres), and Truma Combi (10 litres).

The advantage is simplicity and proven reliability. The disadvantage is running out of hot water mid-shower. With a 14-litre tank, you’ll get one decent shower (5-7 minutes) before the water starts cooling. A 22-litre tank handles two consecutive short showers. The Truma UltraRapid partly solves this by continuously reheating while you’re showering, so if you’re not using water at full flow, it keeps up reasonably well.

Instantaneous (Tankless) Systems

Instantaneous systems heat water on demand as it flows through the unit. There’s no tank to empty, which means endless hot water as long as you have fuel. The Truma AquaGo is the premium option here, featuring microprocessor-controlled burner management that maintains a constant outlet temperature regardless of flow rate. You set your preferred temperature (up to 49°C) on the control panel and the system adjusts automatically. No more fiddling with taps to find the right mix.

The AquaGo also eliminates the classic instantaneous heater problem of temperature fluctuation. A small 1.3-litre stabiliser tank smooths out the temperature variations that plague cheaper instant systems. The Camec Digital Instant is a more affordable alternative but has a reputation for being sensitive to water pressure, so check reviews carefully before committing.

Instantaneous systems cost more upfront (the AquaGo kit runs around $1,800-2,200 installed) but the endless hot water supply is genuinely life-changing for families or anyone who values a long shower.

How to Identify What’s in Your Van

If you’ve bought a used caravan or haven’t paid much attention to the hot water setup, identifying your system is straightforward. Walk around the outside of your van and look for an access panel, usually a square door about 450mm x 450mm on the lower half of a sidewall. The brand name is typically printed on the door or visible when you open it.

Truma units have a distinctive grey or black plastic access door. The model name (UltraRapid, AquaGo, Combi, Boiler) is usually printed on the inner frame. Truma also has a control panel inside the van, often near the bathroom, where you switch the system on and select gas, electric, or both.

Suburban units have a metal access door with a stamped or printed model number (SW4D, SW6DE, etc.). The “SW” prefix is Suburban’s signature. Control is usually via a simple rocker switch inside the van.

If you have a Truma Combi, your hot water and cabin heating are built into a single unit installed under a seat or bed inside the van. The Combi heats 10 litres of water and provides ducted warm air heating, with the option to use either function independently. The external access panel is smaller than standalone hot water units, and the ducted heating outlets throughout the van are a giveaway.

Getting the Most From Your Hot Water System

Managing Gas Consumption

On a typical big lap, your gas bottles serve multiple duties: cooking, hot water, heating (if gas-fired), and potentially your fridge if it’s a three-way model. Hot water is usually the biggest consumer. A pair of 9kg gas bottles will last a couple 2-4 weeks depending on how frequently you shower and whether you’re also using gas for heating.

To stretch your gas further: heat water only when you need it rather than leaving the system on all day; switch to electric heating whenever you’re on a powered site; and keep showers to a reasonable length. Navy showers (wet, tap off, soap up, rinse) use a fraction of the water and gas of a continuous flow shower.

Temperature Settings

Storage systems heat water to around 60-70°C, which is then mixed with cold water through a tempering valve to deliver a safe outlet temperature below 50°C. This is a legal requirement and a safety feature: water above 50°C can cause scalding in seconds. Don’t tamper with tempering valves. If your water feels lukewarm rather than hot, the tempering valve may need adjustment or replacement by a licensed plumber, not removal.

Water Pressure Considerations

Instantaneous systems are sensitive to water pressure. Too much pressure (common when connected to mains water at a caravan park) can damage the unit. Too little pressure (common with on-board pumps in older vans) can prevent the system from firing. If you have an instantaneous system, always use a pressure regulator when connecting to mains water, and ensure your on-board pump delivers adequate, consistent pressure.

Common Problems and How to Fix Them

System Won’t Ignite

The most common issue. Check the obvious first: is the gas turned on at the bottles? Is the gas bottle empty? Is the switch inside the van actually on? Beyond that, the most likely culprits are a flat ignition battery (some systems use a separate battery for the spark ignitor), a dirty or corroded ignition electrode, or a faulty gas solenoid. If the system has been sitting unused for months, the gas line may have air in it. Turn the system on, wait 30 seconds, turn it off, then try again. It can take 3-4 cycles to purge air from the line after a long idle period.

Water Not Getting Hot Enough

If the system ignites and runs but the water never reaches proper temperature, the tempering valve may be set too low (or stuck), the heating element may be failing (electric systems), or the gas flame may be weak due to a partially blocked burner jet. Mineral scale buildup inside the tank also reduces heating efficiency over time. Truma recommends descaling twice a year, and any storage system benefits from an annual flush.

Running Out of Hot Water Too Quickly

With storage systems, this is often just a capacity issue rather than a fault. A 14-litre tank delivers about 5-7 minutes of showering depending on flow rate. If you’re consistently running out, consider reducing your shower flow rate (low-flow shower heads make a real difference), waiting longer between the system finishing its heating cycle and showering, or upgrading to a larger tank or instantaneous system.

Anode Rod Maintenance

Suburban storage systems use a sacrificial anode rod to protect the tank from corrosion. This rod needs checking annually and replacing when it’s worn to about half its original diameter. Neglecting the anode will shorten the life of your tank significantly. Truma UltraRapid systems use a stainless steel tank and don’t require an anode, but they do need regular descaling instead.

When to Consider an Upgrade

If your current system is working well and meeting your needs, there’s no pressing reason to change it. Upgrades make sense when your system is failing, when it can’t keep up with your family’s hot water demand, or when you want to change fuel sources to suit a different travel style.

The most common upgrades are:

Gas-only to gas/electric: If you have a Suburban gas-only unit and regularly stay at powered sites, upgrading to a gas/electric model means you stop burning gas when mains power is available. The Suburban SW6DE is a straightforward swap and uses the same mounting cutout as most gas-only Suburban models.

Storage to instantaneous: The Truma AquaGo is designed to fit the same cutout as common Suburban units, making it a relatively clean retrofit. The endless hot water supply is the single biggest quality-of-life upgrade you can make if you’re a family of four sharing one shower. Budget $1,800-2,200 for the unit and installation.

Adding a Truma Combi: If you need both cabin heating and hot water and don’t currently have either done well, the Truma Combi 4E or 6E combines both functions into one unit. It’s a significant install (the unit goes under a seat or bed, with ducted outlets throughout the van) but eliminates the need for separate heater and hot water units. Budget $3,000-4,000 installed for the gas/electric version.