A campervan water tank is a warm, dark container that is often left half full between trips, which is exactly what bacteria and biofilm like. Cleaning and sterilising the whole system (tank, pump, pipes, taps, shower and any water heater) is a short job once you know the order. It is worth doing even if you only drink bottled water.
This guide covers why it matters, which products to use (and avoid), a step-by-step routine, how often to repeat it and how to keep the water fresh between cleans. If you are still building your system, start with our campervan water tank and pump setup guide. Always follow the label of the product you use and the instructions for your water heater.
Why sterilise a campervan water system?
The Caravan and Motorhome Club’s technical team says its microbiological testing found that poorly sterilised leisure-vehicle water systems were more likely to cause a mild respiratory infection than a stomach upset. You can catch this by breathing in water vapour from the sink or shower, so using bottled water for drinking does not make you immune. The Club also found appreciable contamination after just a few weeks of non-use.
The Foundation for Water Research (FWR) guide to water for leisure boats and caravans explains that stored water is not inert. It can support microbial growth, and non-approved DIY materials, particularly some flexible pipe, can build up visible biofilm: a slimy mix of bacteria, mould and other microorganisms that causes tastes, smells and even bits in the water. Its rule of thumb is simple: “if in doubt, flush it out”.
What to use, and what to avoid
| Product | Use it? | Notes |
|---|---|---|
| Proprietary leisure-vehicle steriliser (for example Puriclean) | Yes, the safest default | Made for tanks, pipes, pumps and taps. Clean Tabs says Puriclean cleans and sterilises, is left to soak for 1–12 hours, and can be used in systems with stainless steel boilers and aluminium tanks. |
| Chlorine sterilising fluid or tablets (baby-bottle type) | Only if your heater and tank allow it | FWR calls chlorine “the disinfectant of choice” for water systems but warns it can corrode metal parts in water heaters and degrade polyurethane flexible tanks. Truma says chlorine products are not suitable for its water heaters. |
| Household bleach | No | FWR says many household bleaches contain additives that make them inappropriate for drinking-water systems. |
| Vinegar | Not as a disinfectant | FWR says vinegar has very little disinfecting ability and leaves a strong taste. Vinegar essence or citric acid can be used for descaling heaters, which is a different job. |
| Camden / metabisulphite tablets | No | FWR notes these mainly remove chlorine; they do not disinfect. |
Check your water heater first
If your van has a Truma Therme, Boiler or Combi, Truma’s own maintenance guidance recommends commercially available cleaning and sterilising products and says that products containing chlorine are not suitable. It also recommends heating the boiler water to 70 °C at regular intervals to help prevent microorganisms. On a Combi E, set the water to 60 °C in gas mode, leave it on for at least 30 minutes without drawing hot water, and residual heat takes it to 70 °C. Other heater brands have their own instructions, so read yours before choosing a product.
Before you start: checklist
- A leisure-vehicle steriliser suited to your tank size and heater (check the dose on the pack).
- Enough clean drinking water to fill the tank or container at least three or four times.
- A funnel and a clean filling hose kept only for drinking water.
- Somewhere suitable to drain into (a site drain or waste point, not a river or ditch).
- Access to the tank drain, all taps, the shower and the heater drain valve.
- Rubber gloves; concentrated sterilisers can irritate skin.
- A replacement filter cartridge if you run an inline or carbon filter.
How to clean and sterilise a campervan water tank: step by step
These steps combine the guidance from FWR, the Caravan and Motorhome Club and the published Puriclean method shown by Caravan Guard. Your product’s instructions override any general step here.
1. Drain everything
Switch off the water heater and let it cool. Open the tank drain and every tap (hot and cold) and the shower. FWR points out that water cannot pass back through a diaphragm pump, so on a fixed-tank system you need to run the pump until no water comes from any tap, then switch it off. Open the heater drain valve as its manual describes.
2. Remove filters
Take out any water filter cartridges before sterilising. Both FWR and the Caravan and Motorhome Club say to remove them first or replace the element afterwards, because the steriliser can damage the filter and the filter is not a substitute for cleaning.
3. Clean what you can reach
If the tank has an inspection lid, look inside. Physically clean taps, hose ends and fillers before disinfecting them. FWR says surfaces should be cleaned before a disinfectant is applied. For a removable container, rinse it out with drinking water.
4. Mix the solution and fill
Close the tank drain and heater drain. Add the steriliser at the dose on the pack for your tank volume, then fill with drinking water. Caravan Guard’s guide quotes the Puriclean pack as one teaspoon per four and a half litres. Clean Tabs states the 100 g tub treats tanks up to 90 litres and the 400 g up to 360 litres. If you have a portable container, mix the solution in it and connect it as though filling from dry.
5. Draw it through every outlet
Switch the pump on and open each tap and the shower, hot and cold, until the solution comes through, then close it. A common tip is to start at the outlet farthest from the tank and work back. Do not forget the hot side: FWR warns that Legionella bacteria can grow in warm, stagnant water such as rarely used shower heads.
6. Leave it to soak
Follow the product’s contact time. Clean Tabs gives 1–12 hours for Puriclean. For a chlorine solution, FWR suggests charging the system at 50 mg/l and leaving it for at least 8 hours, preferably a day, but only where your heater and tank materials allow chlorine.
7. Drain and flush
Drain the tank and run the solution out through every outlet. Refill with fresh water and flush again. Caravan Guard repeats this two or three times. Keep flushing until the water no longer smells or tastes of the steriliser at any tap.
8. Refit filters and refill
Fit a new or cleaned filter element, close the drains and refill with fresh drinking water. If you are storing the van, drain the system down instead and leave the taps open, which protects against frost as well.
Don’t forget the bits outside the tank
- Filling hoses and containers. The Caravan and Motorhome Club says to include external fresh-water containers and connecting hoses in your routine. For containers, FWR suggests filling them completely with a 50 mg/l chlorine solution for at least 15 minutes, then rinsing well and leaving them upside down to drain somewhere clean.
- Shower heads. Run them during the sterilise and flush stages; they are a classic spot for stagnant warm water.
- Clear pipe. FWR notes algae can grow in clear plastic tubing exposed to daylight, even if approved, so keep pipe runs covered or use opaque pipe.
How often should you sterilise?
No single interval suits every van. The Caravan and Motorhome Club says it is “probably more often than you think” and recommends sterilising again after any significant period of non-use, not just at the start of the season. Treat these as minimum triggers:
- When the van comes out of storage or after winter drain-down.
- After a few weeks of not using the system.
- If the water smells, tastes odd, or you see slime or particles.
- After filling from a source you are not sure about.
- After any work on the tank, pump or pipework.
Keeping the water fresh between cleans
- Turn it over. Lifesure’s motorhome water tank guide advises not leaving water in the tank for more than three days and refilling every one to three days.
- Fill from the right tap. Use taps marked as drinking water and keep your hose off the ground. FWR advises a backflow preventer and checking any hose already attached to a site tap.
- Use approved materials. FWR recommends WRAS-approved pipe and fittings even when not connected to the mains, because non-approved materials can support bacteria and cause taste or odour.
- Drain before storage. Drain down the whole system, including the heater, before frost or long lay-ups.
- Keep hot water hot. If your heater maker recommends periodic heating to 70 °C, as Truma does, build it into your routine.
If you are planning your build, think about access now: a tank with an inspection lid and a reachable drain, plus a pump you can isolate, makes this job much easier. Our UK van conversion walkthrough covers where the water system fits in the build order, and the 12V electrics guide covers fusing and switching the pump circuit.
FAQ
Can I use Milton to sterilise my campervan water tank?
Baby-bottle sterilising fluid is a chlorine solution. FWR lists chlorine solutions sold for sterilising babies’ bottles as acceptable for water systems, but warns chlorine can corrode metal heater parts. Truma says chlorine products are not suitable for its heaters. If you have a heater, check its manual; a product marketed as safe for leisure-vehicle water systems and your heater is the safer choice.
Can I use household bleach?
No. FWR says many household bleaches contain additives that make them unsuitable for drinking-water systems.
Is vinegar good enough?
Vinegar is not a disinfectant in this context; FWR says it has very little disinfecting ability and leaves a strong taste. It, or citric acid, can descale a heater if the manufacturer allows it, but that is separate from sterilising.
How long should I leave the steriliser in the tank?
Follow the label. Puriclean gives 1–12 hours. FWR suggests at least 8 hours, preferably a day, for a 50 mg/l chlorine solution where chlorine is appropriate.
Is the water safe to drink afterwards?
Once flushed until there’s no smell or taste of the product, refilled from a drinking-water tap, and with a fresh filter fitted, the system is clean. Many owners still drink bottled water or boil tank water, as Lifesure suggests, because you cannot control every site tap or hose.
Do I need to sterilise a removable water container?
Yes. The Caravan and Motorhome Club specifically says to include external containers and filling hoses, and FWR gives a short container routine (see above).