Your fresh water tank can develop biofilm, algae, and bacteria over time, particularly in warm conditions. A tank that hasn’t been cleaned tastes off and can make you sick. Cleaning every 3 to 6 months (or after any period of non-use longer than 2 weeks) keeps your water fresh and safe.
When To Clean
Every 3 to 6 months during regular use. Immediately if the water tastes or smells unusual. After any period where the tank has sat full and unused for more than 2 weeks. Before your first trip if the van is new (tanks can contain manufacturing residues). After filling from a questionable water source.
How To Clean Your Tanks
Step 1: Drain
Empty the tank completely through the drain valve (usually underneath the van). Open all taps to flush the lines. If your van has a hot water system, drain that too.
Step 2: Fill With Cleaning Solution
Fill the tank with clean water and add a sanitising agent. Options include:
Thetford Fresh Water Tank Cleaner ($15 to $25): Purpose-made for caravan tanks. Follow the instructions on the bottle — typically one dose per 40 litres. The easiest option with no guesswork on concentration. Available from most caravan accessory stores.
Puriclean Tank Cleaner ($10 to $18): Another purpose-made caravan tank sanitiser. Particularly effective against biofilm and algae. Widely available online and at caravan dealers.
Milton Sterilising Tablets ($8 to $12 from the supermarket): The budget DIY option. 2 tablets per 10 litres of water. Originally designed for sterilising baby bottles, so perfectly safe for water systems. Effective and cheap.
Sodium Percarbonate ($8 to $15 per kg from cleaning supply stores): An oxygen-based cleaner that breaks down biofilm without leaving chemical residues. 1 tablespoon per 10 litres. Rinses clean easily. The preferred option for many long-term travellers.
Do not use bleach in high concentrations; it can damage tank fittings and leave residual taste.
Step 3: Circulate
Run the solution through all taps (hot and cold) until you can smell the cleaning agent. This cleans the lines and fittings, not just the tank. Let the solution sit in the tank for 4 to 12 hours (overnight is ideal).
Step 4: Drain And Rinse
Drain the cleaning solution completely. Fill with fresh water and drain again. Repeat the rinse until you can’t taste or smell any cleaning agent. Run all taps to flush the lines.
Step 5: Refill
Fill with fresh, potable water. Your tank is now clean and ready for use.
An inline water filter on your tank inlet reduces the contamination entering your tank in the first place, extending the time between deep cleans. The Camec Inline Carbon Filter ($30 to $50) is the most popular basic option and removes sediment, chlorine taste, and odour. For more thorough filtration, the Doulton Rio 2000 ($150 to $250) or Puretec Caravan Kit ($200 to $300) offer multi-stage filtration that handles bacteria and finer particulates. A good filter makes town water taste noticeably better and protects your tank from accumulating contaminants.
Clean your water tanks every 3 to 6 months using a tank cleaner or Milton tablets. Drain, fill with solution, run through all taps, let sit overnight, then rinse thoroughly. An inline filter on the inlet reduces contamination between cleans.
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