Caravans and motorhomes are some of the hardest vehicles to dry after washing. You are dealing with large, flat panels, roof-mounted solar panels, awning rails, and decals that trap water. Every missed spot leaves a mineral stain when the water evaporates.
The fix is surprisingly simple: use deionised (DI) water for your final rinse.
Why Caravans Are Worse for Water Spots Than Cars
A sedan has roughly 8-10 square metres of exterior surface. A typical caravan has 25-40 square metres, three to four times the drying area. Add in:
- Flat roof panels that pool water
- Solar panels where mineral deposits reduce efficiency
- Awning tracks and rails that trap water and streak as it runs out
- Vinyl decals and graphics that show every water mark
Hand-drying all of this is a 30-60 minute job, and you will still miss spots. In Australian summer heat, the water dries faster than you can wipe it.
How Deionised Water Solves the Problem
DI water has had all dissolved minerals removed through ion exchange resin. When it evaporates, nothing is left behind, no calcium, no magnesium, no spots.
The process:
1. Wash your caravan with normal tap water and caravan shampoo as usual
2. Rinse off all soap with tap water
3. Switch to DI water through the bypass valve on your tank
4. Final rinse every panel, the roof, solar panels, windows, and wheels with purified water
5. Pack up: the water air-dries completely clean
A full caravan rinse typically uses 40-60 litres of DI water. An XL 25-litre resin tank produces 6,700-7,500 litres at 100 ppm input, enough for over 100 caravan washes before the resin needs replacing.
Best Tank Size for Caravan Owners
| If you wash... | Recommended tank | Why |
|---|---|---|
| One caravan fortnightly | Medium 10L | Good balance of capacity and portability |
| Caravan + tow vehicle together | Large 15L | Handles both in one session |
| Multiple vehicles or commercial use | XL 25L | Maximum resin life between replacements |
The Medium 10L is the most popular choice among caravan owners. It produces 2,550-2,900 litres of pure water at typical Australian water hardness, enough for 40-50 full caravan rinses.
Tips for Spot Free Caravan Washing
- Wash in sections: roof first, then sides top-to-bottom, then front and rear
- Use a water fed pole for the roof instead of climbing up. A pole with DI water cleans and rinses in one step
- Do the final DI rinse last: never go back to tap water after the DI rinse
- Check your TDS meter before each wash to confirm the resin is still producing 0 ppm water
- Flush the tank for 10-15 seconds before starting if it has been sitting for more than a week
What About Caravan Parks and Travel?
The Medium 10L tank is portable enough to take on the road. They connect to any standard Australian garden hose fitting, the same fittings found at most caravan park wash bays.
Fill up with tap water from the park’s supply, connect your DI tank for the final rinse, and you have a spot free van without carrying chamois cloths, spray bottles, or drying aids.
If you wash at home, it is worth checking your local rules first. Most councils have no problem with washing a van in your driveway or on the lawn, but soapy runoff entering the stormwater drain can attract a fine. Our state by state guide to home car washing rules and water restrictions in Australia covers what applies in your area.
Solar Panels on Your Caravan Roof
Mineral deposits from tap water reduce solar panel efficiency over time. When you rinse your caravan roof with DI water, you are also cleaning the solar panels with zero-residue water, maintaining maximum output without any extra effort.
Travelling? Our Big Lap caravan washing guide covers salt, dust, park rules and keeping the van clean on the road.
