I’ve heated four campervans. Three of them had separate heating and hot water systems. The fourth, my Fiat Ducato has a Truma Combi Boiler. And honestly? I wish I’d made the switch two builds ago.
This isn’t some sponsored love letter to Truma. I bought the unit with my own money after spending three builds mucking about with Chinese diesel heaters, separate water boilers, and the sort of plumbing nightmares that wake you up at 3am wondering if you’ve created a death trap. The Truma Combi costs more. A lot more. But after 18 months of testing it against my previous heating setups, I can tell you exactly why it was worth every penny and when it absolutely isn’t.
The Heating Journey: Vans 1 to 3
Let me walk you through what I learned the hard way.
2017 VW Transporter had no heating at all. Just a £3,000 budget and youthful optimism. Took it to Scotland in February 2018. Water tanks froze solid. Spent three nights shivering in a sleeping bag rated for summer camping. Learned that “weekends away” in a British winter requires actual heating, not just extra jumpers.
2019 Ford Transit got a Chinese diesel heater, one of those £120 units off eBay that everyone raves about on YouTube. For hot water, I installed a separate 10L Elgena electric boiler that ran off shore power or a 1500W inverter. Total cost: around £280 for both systems. Sounded brilliant on paper.
Reality? The diesel heater worked perfectly for about 8 months, then started throwing error codes. Fuel pump failed twice. Got it sorted each time, but it meant stripping out furniture to access the unit under the bed. The Elgena boiler was fine—when I had shore power. Which was about 30% of the time. Running it off the inverter drained my 200Ah AGM battery bank in under 2 hours. So most mornings involved heating water in a kettle like some sort of Victorian scullery maid.
2022 Mercedes Sprinter was where I thought I’d cracked it. Upgraded to a Webasto Air Top 2000 STC (£850 from a proper supplier, not eBay). Absolute workhorse. Quiet, reliable, properly engineered. For hot water, I installed a Propex WH2000 gas water heater (£520). Two separate systems, two different fuel sources, two different sets of venting requirements.
Both systems worked perfectly. I had no mechanical failures across two years of use. But the installation was a nightmare—diesel flue and air intake for the Webasto, gas flue for the Propex, separate controls, separate programming, separate maintenance schedules. The plumbing alone took me four weekends because I had to route hot water pipes from the Propex (mounted near the rear doors for gas locker access) all the way to the kitchen tap up front.
And here’s the thing nobody mentions: having two separate systems means two potential failure points. The Webasto failed while I was in the Lake District in January 2024. Nothing catastrophic, just a glow plug that needed replacing. But without heating, I also lost hot water indirectly because I wasn’t willing to run the Propex without having the Webasto available as a backup heat source. Ended up cutting the trip short.
That’s when I started researching combination units.
What Actually Is a Truma Combi?
The Truma Combi Boiler is a combined blown-air heating and hot water system that runs on either LPG gas or mains electric (the “E” models). One box does both jobs. It heats your van’s living space and provides hot water for your taps and shower.
The unit I installed is the Truma Combi 6E (Part Number J46789 / OEM Part Number 33516-78, £1795.00 at time of purchase from Just Kampers. The “6” means 6kW heating output. The “E” means it has a 230V electric heating element for when you’re on shore power.
Here’s what’s inside that grey plastic box:
- 10-litre stainless steel hot water tank
- LPG gas burner (6kW heat output)
- 1800W electric heating element (for shore power)
- Blown-air fan and ducting outlets
- Electronic control system with room thermostat
- Frost protection mode
- Built-in expansion relief valve
The whole unit weighs 17.5kg empty. It’s 513mm long, 345mm wide, and 246mm tall. Not small, but smaller than having a separate diesel heater and water boiler taking up space in different parts of the van.
The Installation Reality Check
Let me be straight with you: installing a Truma Combi is not a Saturday afternoon job. This is a proper weekend project, possibly stretching into a second weekend if you’re doing it solo like I did.
You’ll need gas certification for the LPG connection. That’s non-negotiable. I did everything else myself, mounting, ducting, water plumbing, electrical – but the final gas connection was done by a Gas Safe registered engineer (cost me £180 for his time). He pressure-tested the system, issued the certificate, and I sleep better knowing a professional checked that bit.
What you’ll need:
The unit itself comes with mounting brackets and a basic instruction manual that’s actually quite good. What it doesn’t come with:
- Heating ducting and outlets (I used 60mm Truma ducting, about £65 for 3 metres)
- 12mm water inlet and outlet pipes (John Guest push-fit, £23)
- 230V mains cable and connection (2.5mm Arctic flex, £18)
- Gas supply pipe and regulator (installed by Gas Safe engineer)
- 12V power supply to control panel (ran from my 12V fusebox)
- Drainage pipe for condensate (just some 10mm waste pipe I had lying about)
Total additional parts: around £290 on top of the unit cost.
The actual installation process:
I mounted the Combi under my offside seating area, which doubles as a storage box. The unit needs to be mounted level – there’s a spirit level built into the mounting bracket specifically for this. It also needs access to:
- LPG gas supply
- 230V shore power (if you’re using the electric element)
- 12V power for controls and fan
- Fresh water inlet
- Hot water outlet
- Heating duct outlets
- External flue
That’s seven different connections. Compare that to a Chinese diesel heater (fuel in, exhaust out, 12V power) and you start to see why this takes longer.
The flue installation is critical. Truma provides a specific flue terminal that must be mounted on an exterior wall, horizontally, with a slight downward slope for condensation drainage. Mine exits through the van’s side wall about 300mm from the floor. You’ll want it as low as practical because the flue gets hot—mounting it near windows or plastic trim is asking for trouble.
I used a 60mm hole saw for the flue penetration. Sealed it with Sikaflex 252 (the same stuff I use for window installations, because I trust it). Let it cure for 24 hours before running the system.
Water connections are straightforward if you’re already familiar with John Guest fittings. Cold water in, hot water out. The Combi has built-in non-return valves, which is brilliant because it means you don’t need separate check valves in your plumbing. Just connect and done.
The heating ducting took me longest. I ran 60mm ducting to three outlets: one under the front seats (driver and passenger areas), one mid-van (seating/living area), and one rear (bedroom area). Each duct run needs to be as short and straight as possible—every bend reduces airflow efficiency. I used adjustable outlet grilles (£8.50 each from Amazon UK) so I can direct heat where it’s needed.
Common installation mistakes I nearly made:
Mounting it too high. The Combi is heavy when full of water (27.5kg loaded). I initially planned to mount it up near the roof for space reasons, but the mounting instructions specifically warn against this—the weight stress on the brackets isn’t designed for overhead mounting.
Undersizing the gas supply. The Combi needs a 30 mbar gas regulator and 8mm gas pipe minimum. I nearly used 6mm pipe because that’s what I had left over from a previous build. Would have restricted gas flow and caused the burner to underperform.
Forgetting the condensate drain. The unit produces condensation that needs to drain away. There’s a small outlet on the bottom of the unit for this. I ran a 10mm pipe from this outlet straight through the floor. Without it, you’ll get water pooling inside the unit housing.
How It Actually Works in Practice
Right. Theory is one thing. But does it actually heat the van and provide hot water reliably? After 18 months and roughly 15,000 miles of testing, here’s the reality.
Heating performance:
The 6kW output is spot-on for my high-top Ducato (internal volume roughly 11 cubic metres). At -2°C outside temperature, it takes about 25 minutes to bring the van from freezing to 18°C. That’s with the thermostat set to 20°C and all three heating ducts open.
Fan noise is noticeable but not intrusive. On maximum fan speed, it’s about as loud as a household bathroom extractor fan. You can hold a conversation over it, but you wouldn’t call it silent. The Chinese diesel heater was quieter, I’ll give it that. But the Webasto was actually louder, so this sits in the middle.
Running on gas, the Combi uses approximately 385g of propane per hour at full output. I’ve got a 6kg refillable gas bottle. In theory, that’s 15.5 hours of continuous running. In practice, the thermostat cycles the burner on and off, so I get closer to 30-40 hours of heating from one bottle in winter conditions.
For comparison, the Webasto diesel heater used about 0.25 litres per hour, which worked out cheaper per hour of heat. But I was carrying diesel anyway for the engine, whereas gas serves multiple purposes (cooking hob, gas heating, hot water). The economics depend on your specific setup.
Hot water performance:
This is where the Combi absolutely smashes separate systems. Ten litres of hot water, heated to 60°C in about 20 minutes from cold on gas, or 40 minutes on the electric element.
Ten litres doesn’t sound like much, but it’s genuinely enough for:
- A 5-minute shower (using an Ecocamel shower head at 6 litres per minute, you’ll use about 4-5 litres total of mixed hot/cold water)
- Washing up after a meal for two people
- A quick wash in the sink
If you run out, you just wait 20 minutes for the next batch. With the separate Elgena boiler ive previously used, I had the same 10L capacity but it took 50 minutes to heat on 230V power and drained my batteries if I used the inverter. The Propex heater was instantaneous (on-demand heater) but needed the taps running to trigger it, which wasted water while you waited for hot water to arrive.
The Combi’s tank stores heat. Open the tap, hot water comes out immediately. No waiting, no wasted water running down the drain while the system fires up. That alone makes it worth having for someone like me who primarily camps off-grid.
Frost protection:
This feature saved my arse in the Cairngorms last winter. The Combi has a built-in frost protection mode that monitors the water temperature. If it drops towards freezing, the system automatically fires the burner just enough to keep the water above 4°C.
I’d left the van parked for three days while I was in the Austrian alps. Came back to -8°C overnight temperatures. Every other van in the car park had owners frantically draining their water systems. Mine? Still functional. The Combi had used about 800g of gas keeping itself from freezing, but everything worked perfectly.
Compare that to my first build where my tanks froze solid, or even my third attempt where I had to manually drain the Propex every time temperatures dropped, and you start to see why I’m willing to pay for this level of automation.
Electric heating mode:
When hooked up to shore power, you can switch the Combi to electric-only mode. The 1800W element heats the water tank and provides some space heating through the blown-air system, though it’s not as powerful as the gas burner.
I use this when I’m on a campsite with electric hook-up (EHU). It’s “free” heat (included in your pitch fee), it’s silent, and it doesn’t use gas. The 1800W draw is well within the typical 16A campsite supply (3,680W maximum).
The electric mode won’t heat the van as quickly as gas—it’s more of a “maintain temperature” setting than a “warm up from freezing” setting. But for overnight heating when you’re already warm and just want to maintain 16-18°C, it’s perfect.
The Money Question: Was It Worth £2,137.32?
Let’s break down the actual costs:
Truma Combi 4E unit: £1795.00
Additional installation parts: £290.00
Gas Safe certification: £180.00
Total: £2,265.00
For comparison, here’s what I spent on the third builds separate systems:
Webasto Air Top 2000 STC: £850.00
Propex WH2000 gas heater: £520.00
Installation parts for both: £340.00
Total: £1,710.00
The Truma cost £555.00 more. That’s 1/3 more expensive.
But here’s what that extra money bought me:
Simplified installation: One unit to mount, one flue to install, one control system to wire up. The labour saving was substantial—I estimate the Combi installation took me about 60% of the time that installing two separate systems took in my third build.
Reduced complexity: Fewer potential failure points. Fewer things to maintain. Fewer systems to understand and troubleshoot.
Better integration: The heating and hot water share the same fuel source and electrical supply. No separate timers, no separate controls, no confusion about which system does what.
Frost protection: This alone has saved me from potential damage that would have cost more than the price difference to repair.
Resale value: I plan to sell this van eventually when im ready to build my 5th and final van happens. A professionally-installed Truma Combi with Gas Safe certification is a selling point that commands a premium over DIY separate systems.
Would I recommend it for everyone? No.
If you’re on a tight budget and doing a basic weekend warrior build, a Chinese diesel heater and a kettle will get you through. Save your money.
If you’re doing a more serious build but primarily camping in summer, you might not need the frost protection or the complexity. A simpler system makes sense.
But if you’re building for year-round use in the UK, particularly if you plan to leave your van parked in winter conditions, or if you value reliability and integration over saving a few hundred quid, the Truma Combi is the single best heating investment I’ve made across four builds.
Common Questions and Reality Checks
“Can I install it myself without Gas Safe certification?”
Legally, no. Any LPG gas connection in a habitation vehicle must be installed and certified by a Gas Safe registered engineer. You can do everything else – mounting, ducting, water plumbing, electrical – but the gas connection must be certified.
Could you physically do it yourself? Yes. Should you? Absolutely not. Gas leaks in confined spaces kill people. The £180 I paid for certification is cheap insurance against ending up as a cautionary tale on a van life forum.
“Does it work with refillable gas bottles?”
Yes. I use a 6kg bottles with a standard 30 mbar regulator. The Combi doesn’t care where its propane comes from as long as the pressure and flow rate are correct.
“What about running it while driving?”
The Combi can technically run while the vehicle is moving, but Truma recommends against it for safety reasons. The gas supply should be turned off while driving. In practice, I heat the van thoroughly before setting off, and the insulation keeps it warm for 2-3 hours of driving in winter.
“How often does it need servicing?”
Truma recommends annual servicing by an authorized technician. This involves checking the burner, cleaning the flue, inspecting gas connections, and descaling the hot water tank if needed. Cost is typically £120-150. I’ve had one service so far (at 12 months) and everything checked out fine.
“Does the 10L tank get limescale buildup?”
Yes, if you’re in a hard water area. I’m in Essex—our water could probably be used as building aggregate. I descale the tank every six months using Oracstar Liquid Descaler (£6.50 from my local Screwfix in Braintree). Takes about 30 minutes, involves draining the tank, filling it with descaling solution, letting it sit for an hour, then flushing thoroughly.
“What’s the 12V power draw?”
The control panel and fan run on 12V. At maximum fan speed, it draws about 2.8A (34W). At minimum fan speed, about 0.9A (11W). The gas ignition system draws about 10A for 3-4 seconds during startup, then drops to nothing once the burner is running.
Compare this to diesel heaters which draw 8-10A continuously while running, and the Truma is actually more efficient if you’re running on gas.
What I’d Do Differently
Even after 18 months, there are things I’d change if I were installing it again:
Ducting layout: I wish I’d run four outlets instead of three. The rear bedroom area doesn’t get quite enough heat with just one duct serving it. I’d add a second outlet specifically for the bed area.
Mounting position: I mounted it under the seating on the offside (passenger side) because that’s where my gas locker is. But this means it’s directly under where my partner sits. The unit generates some radiant heat even though most goes into the ducting. In summer, this makes that seat warmer than you’d want. If I were doing it again, I’d mount it further back, maybe under the bed base where the radiant heat would actually be beneficial.
Control panel placement: I mounted the control panel on the kitchen unit about 2 metres from the Combi. This works fine, but the cable supplied is 2.5 metres and I’ve used almost all of it. An extra metre of slack would have given me more flexibility in positioning.
Hot water outlet placement: The hot water outlet on the Combi is on the right-hand side of the unit (facing it from the front). My kitchen is on the left side of the van. This meant running hot water pipes across the width of the van to reach the tap. If I’d mounted the unit reversed, I could have cut that pipe run by about a metre.
The Honest Verdict After 18 Months
I’ve heated vans with Chinese diesel heaters (£120), with Webasto diesel heaters (£850), with separate gas water heaters (£520), and now with the Truma Combi (£1795).
The Combi is the best heating solution I’ve used. Not the cheapest. Not the most powerful per pound spent. But the best in terms of overall functionality, reliability, and peace of mind.
It just works. Turn the thermostat to your desired temperature, and the van gets warm. Open the hot water tap, and hot water comes out. Park in freezing temperatures for a week, and it protects itself. That level of integration and automation is worth paying for when you’re using the van year-round in British weather.
Would I fit one in my next build? Absolutely. In fact, I’m already looking to install the Truma Combi 6E (6kW output) for what will be a longer wheelbase and hightop van. Because once you’ve experienced the simplicity of a combination system done properly, going back to separate heating and hot water feels like a backward step.
The Chinese diesel heaters will always have a place in budget builds. The Webasto and Eberspacher diesel heaters will always be brilliant for people who prioritize efficiency and want separate heating control. But for someone who wants reliable heating and hot water from one integrated system, with frost protection and dual fuel capability, the Truma Combi is the only choice I’d make now.
Just budget for it properly, get the gas work certified, and don’t skimp on the installation. Done right, it’s the last heating system you’ll need to install.
Affiliate Disclosure: This article contains affiliate link to Just Kampers. If you purchase through this link, I earn a small commission at no extra cost to you. I only recommend products I’ve tested across my four van builds or would confidently use in my next build. The Truma Combi 6E mentioned in this article was purchased with my own money – nobody paid me to write this. Your support keeps this site independent and ad-free.
