How can you keep the water tank in your motorhome or caravan clean?

January, 2 2018

If you’re planning on a trip with your motorhome or caravan, a full water tank is indispensable. Although we don’t advise that you drink the water from the tank, it’s still important to keep not just the water itself but also the tank clean. This way you can prevent the growth of all kinds of unpleasant bacteria. Many campers don’t realise this, so we’ve asked Geert de Bekker, an expert on water, to explain the subject to us.


Geert de Bekker, a passionate camper for almost 50 years, has been a motorhome enthusiast for the last 20 years. He knows what concerns campers more than most. Thanks to his 10 years of experience in ozone technology, he’s gained a lot of knowledge about everything to do with clean and safe water. He’s grateful for that experience now as he’s used it to develop applications for water treatment plants and drinking water tanks.


The quality of the water in a water tank rapidly deteriorates. High temperatures in the summer don’t help, as they encourage the growth of harmful bacteria. Bacteria have free rein to multiply rapidly because the water isn’t moving and is in an enclosed space. They nestle against the interior wall and in the tubes of the tank. If you combine this with higher temperatures outside, the water tank becomes an ideal breeding ground for bacteria and mould.

Biofilm in the tank

The result is a slimy residue in the pipes. This mixture of microorganisms is called a biofilm. As a result of the biofilm on the water, both the water and the tank itself shouldn’t be relied upon. Obviously, water safety can’t be taken for granted.

 Eurocampings Newsletter 

Don’t drink water from the tank

You never know how dirty the water pipes are, so it’s safest not to drink water from the tank. This will help you to avoid getting diarrhoea. The water in the pipes is actually the most likely to be dirty. It’s difficult to check whether they’re clean or not, and they’re also the parts of the tank that are most susceptible to getting dirty. In addition, the water is often lukewarm when it comes out of the tank, so it’s less pleasant to drink than fresh cool water. You also need to bear in mind that the quality of drinking water isn’t as good as it is in the UK in lots of other countries. That’s why we advise that you drink bottled water – and if you keep it in the fridge it’s always nice and cool too. If you really don’t have access to any water apart from what’s in the tank, we advise that you boil it for at least 3 minutes before drinking it. That’s how long it takes to kill all the harmful bacteria.


You might be asking yourself, if drinking water from the tank is discouraged, why is it important to keep the tank free from bacteria? The most feared bacterium is the legionella bacterium. If the water in your tank is contaminated with this bacteria, then you can get sick just from showering or drawing water from the tap. That’s because legionella can enter your body when you inhale the mist rising off the water. It won’t necessarily make you sick, but there is a chance that it can, particularly if you’re older. In that case, the chance of complications from certain bacteria is higher. A clean tank as well as clean water prevents these types of bacteria from occurring in the first place.

Clean tank = clean water

Just rinsing the water through the taps every few days and filling the tank with clean water isn’t enough. There are various products for ‘disinfecting’ the water. Using them is a good idea, but they don’t clean the biofilm from the tank itself. The result is that your dirty tank immediately contaminates the clean water that you put in it, and the water still isn’t safe. That’s why it’s important to thoroughly clean the tank itself on a regular basis. Even then, there will still be some traces of dirt in the tank.
Water tanks are usually maintained by adding a cleaning product to them once or twice a season. That’s one way of cleaning the tank, but it’s only temporary, as bacteria will start to grow again after a while. So, in order to keep the tank and the water safe, you really need to keep on top of things. The idea that you don’t have to worry about doing any maintenance to your tank for the rest of the season is a misconception.

Always use a clean water hose to fill the tank up. That’s an easy way to prevent bacteria getting in to your tank in the first place. Of course it’s possible that the campsite or motorhome pitch you’re at doesn’t have a clean water hose. So make sure you bring a watering can with you that you only use to fill your tank with clean water.

 CampingCard ACSI 

New developments

You can see why there was a need to develop a way to keep your water tank clean with as little work as possible. Because which camper wants to spend loads of time keeping the tank clean? Geert, who’s been a camper for almost 50 years, spent a long time researching and developing a system for water purification in the recreation sector. ‘I was looking for an improvement that was both easy and environmentally friendly’.

Always clean and safe

Tank-O3 is a small built-in system for in the water tank of a caravan or motorhome, which works on both 12 and 24 volts. An electric current causes a chemical reaction in the water, whereby oxygen in the water (O2) is converted into ozone (O3). Ozone is an extremely strong oxidant which is both tasteless and odourless – and it makes sure that both the water and the tank itself remain free from bacteria. You clean the pipes before using the appliance, so the pipes also remain clean and safe. As long as you keep the system on continuously during the season, all you need to do is keep the tank filled up. The water that’s in the tank can stay there for the whole camping season without causing any problems.

Want to stay informed with fun and useful camping news? Then sign up for the Eurocampings newsletter!

Anouk Hulsman
  • Author: Anouk Hulsman
  • Impressive countryside, beautiful towns and cities, nice beaches or villages rich in history, there is nowhere that Anouk wouldn't consider visiting in her motorhome. As an experienced camper, she is always happy to share her tips for an unforgettable holiday.


  1. Avatar

    Am fairly new to motorhoming and I am keen to pick up tips from experienced campers

  2. Avatar

    Great advice about water treatment

    • Avatar

      Thank you, Charles!

      • Avatar

        How do you clean the pipes before installing your gadget?
        How to clean all the other parts of the system?
        How is your ‘biofilm’ removed?
        Rubbish article of no practical use!

      • Avatar

        What chemical should I put in my RV water tank to make the water safe ?

  3. Avatar

    I can’t fill my water tank

  4. Avatar

    Is this an advert?

    • Avatar

      We emptied the water tank on our motorhome when we took it off the road for winter. We flushed it through with Puriclean 5weeks ago and went way in it for a rew days and it was fine. We filled it fresh from home before going away last weekend but the water was tainted. We flushed it through thrice but taste just the same. Any ideas on how to solve this problem would be much appreciated. Thank you.

      • Avatar

        Your most likely issue will be your hose pipe. Always use a food grade hose.

      • Avatar

        Your most likely issue will be your hose pipe. Always use a food grade hose to fill your tank.

      • Avatar


    • Avatar

      Certainly looks and reads like an advert.
      €399 for the only recommended ‘fix’ in the article.

  5. Avatar

    Complete and utter rubbish. You are actually encouraging people to buy bottled water which may have been shipped half way across Europe at a huge cost to the environment. People may even be camping in the mountains with fabulous local tap water and then buying bottles from another country! Ignore this rubbish and just clean out the system using Milton and refill regularly.

    • Avatar

      We have spent three years caravaning in Australia, Milton was used on a regular basis to keep pipes and tank sweet, yes there is sometimes a taste of Milton but we were safe. In a country where water is more important than fuel, both were topped up at a start of a day’s travel . As a retired clean water employee, I would be more concerned with the source of the water, as it leaves a high pressure, animal infestations disintegrate at atmospheric pressure, so careful what you drink!

      • Avatar

        It is well known that the use of Miltons can seriously damage your water heater and other metals in the water system – so why not use the recommended products also vinegar can be a good aid. All the best George.

        • Avatar

          Yes. If you put a little Milton on to some stainless steel and leave it you will soon understand what it does to the inside of you stainless steel water heater. You won’t use it again when you have seen that.

        • Avatar

          Absolutely agree with Kevin, suggesting buying bottled water is so wrong for many different reasons.
          Also, using these pages, which we campers believe to be about sharing help and advice, to advertise a product is very disappointing – shame on you ASCI!
          Thanks very much, George T and others for info about Miltons. I was about to flush out my camper, it having stood sadly unused for a couple of months now, with Milton but will now look into vinegar or citric acid options. Thank you.

  6. Avatar

    I read about the use of Milton and bleach and the problems it can cause. The manufacturers of our boiler recommend using citric acid which is tasteless and does not cause any problems with the boiler. This can be bought in powder form from Amazon. I will be using this to clean our water tanks as it is inexpensive and safe.

  7. Avatar

    We have always drank water from out Motorhome onboard tank for the last 25 years. However I have always fitted a filtration system.
    For many years I used the Nature-Pure filter system but due to the increasing costs of replacement canisters I have changed to the 3 M HF10 filter which gives similar protection.

    • Avatar

      Simply use either pure lemon juice or vinegar (I prefer lemon juice as no residual taste) you simply need an acid to rid yourself of alkaline (build up in the tank & pipes)
      1. Good dose of lemon juice depending on size of tank.
      2. Flush through the system thoroughly.
      3. Refill with clean water.

  8. Avatar

    I would exercise caution following the use of an Ozone generator in a caravan or motorhome, in my experience as a water engineer my main issue was always with pipe cleanliness, especially the issues already pointed out by some well informed readers on this thread.

  9. Avatar

    Interesting article but our problem is that we filled our take with a non potable hose and didn’t realise. We couldn’t understand why the water tasted bad.
    Once we realised the cause we’ve flushed and flushed out the tank but can’t get rid of the last taint.
    Any suggestions. The list of contaminants from a non potable hose is horrendous.

  10. Avatar

    Thanks For Sharing this Blog!!


Your email address will not be published. Required fields are marked *

Confidental Infomation