Cleaning the fresh and waste water tanks

In a motorhome, van or converted truck, there is always a “clean” water tank as well as a “gray” wastewater tank.

The fresh water tank is the one that will supply the entire water circuit of the vehicle; boiler, tap(s) and shower(s). It is filled by an opening cap located on the side of the vehicle or by the opening the lit located on the top of the tank itself. To avoid health issues this tank requires regular maintenance.

The dirty water or gray wastewater tank is the one that will store the water after you’ve used it. Draining is usually done via a small tap located at the rear of the vehicle. This tank mainly contains water, but also detergents, food scraps, hair, etc. Its maintenance is mainly used to prevent odors into the vehicle. Because indeed, especially in summer under the effect of heat and / or while driving under the effect of the eddies, odors can go up in all the passenger compartment! Not cool.

We do our best to be green, so the cleaning solutions presented are the least harmful to the environment (even if they are… because of their production). But still as effective! Guaranteed! Well ok, I’ll also will show you the benefits of using chemistry for a deep cleaning of your pipes, which can sometimes be necessary.

You should know that the cleaning of the two tanks is done differently. Indeed, the fresh water tank is intended for consumption so some products are not advised!


Cleaning the fresh water tank

Cleaning the fresh water tub is fundamental, especially if you want to use your tap water for washing your vegetables, brushing your teeth or showering. If you want to drink your tap water, that’s even more than a requirement ! Indeed in this case you will have to purify your water… and you do not want it recontaminated by your tank, do you?

In short, it is always essential to clean your own water tank, no matter how you use your water.


Why should you clean your own water tank?

Roughly speaking, three types of pollutants are found in water: chemical compounds, micro-organisms and particles. Cleaning the tank helps to stop / slow down the development of microorganisms.

Micro-organisms (bacteria, protozoa, etc.) develop very quickly in an aqueous envirojnment. Their development is aided by heat, stagnation and thermal shock. Also, these microorganisms are super intelligent since they manage to form a “biofilm”. Biofilm is a bit like a micro-organic village protected by a wall of bacteria resistant to detergents. A kind of microbial castle! Does the slimy thing on the walls of your tank or hoses sound familiar? This is the biofilm. In addition, this biofilm can contain thousands of pathogenic bacteria, such as Salmonella or the famous E. Coli.


How often should you clean your fresh water tank?

The recommended frequency will depend on the use you make of your vehicle and the quality of the water you use to fill your tank. For some, a cleaning before / after the holidays will be sufficient. For those who live year round and source water that is always polluted, monthly cleaning may be necessary.

Most specialized websites recommend annual or biannual cleaning. This is not really good advice since the frequency of cleaning depends on each individual. It also depends on your purification system, if you have one. Indeed, if you purify your water before it enters the tank through a filter and / or in the tank itself, you will probably not need to clean your tank every month!


My advice: a cleaning every 6 months at least, whether you live in it or not. Then adapt according to the quality of the water you are using. And above all, check your tank as regularly as possible! A quick glance through the inspection hatch takes a few seconds. Plus, regular cleaning promises quick cleaning! Check for the presence of biofilm (sticky, viscous film). If you found some, you’re already above the perfect timing to clean your tank.


How to clean your fresh water tank?

The cleaning step

  • Empty the tank completely
  • Rub with a sponge + water = we try to eliminate a maximum of biofim and all the particles (sand, earth …)

Note : rinsing with clean water without even rubbing allows more than 60% recent biofilm to be removed ! Hence the importance of regular cleaning.

  • Rinse with clean water
  • Rub with a vinegar / baking soda mixture. Try to reach as many nooks and crannies as possible!
  • Rinse again


At this stage, you have already eliminated 90% of the bacteria and other impurities present in your tank. For the more judicious or for those who also wish to clean the pipes and the boiler, go to the disinfection step!


The disinfection step


White vinegar is an antibacterial (acts against microorganisms)

Sodium bicarbonate is a fungicide (acts against fungi, molds)

Hydrogen peroxide is a virucide (acts against viruses, and it perfectly replaces bleach ! In France, one or the other of the solutions is used to disinfect water tanks and pipes )

WARNING! Hydrogen peroxide, like bleach, does not mix with vinegar! The tank must be rinsed and re-rinsed before coming into contact with these products! 


1. Bacteria & descaling

  • Fill the tank with 30/50% water and add 1L of white vinegar. If the water is hot, that’s a plus.
  • Roll! The more roundabouts, the better ?
  • Evacuate the water through the taps: the vinegar must pass through all the taps, shower hoses, water heaters.
  • Rinse. Abundantly. The vinegar does not smell very good, and you will feel this vinegar for a few days just by washing your hands if the rinsing is not done properly (Your tub may be unusable for a few days: the vinegar, it smells, it stays a long time, it’s strong). Plan accordingly!


2. Viruses

  • Your tank must be empty and rinsed well: the vinegar must not be mixed with hydrogen peroxide (because it becomes peracetic acid) or with bleach (there, it becomes chlorine gas).
  • Bleach : spray a solution diluted at 10 mg / l on the walls. Then fill the tank to 100% and leave to submerge for at least 24 hours (recommendations from the French Ministry of Health). Empty through the taps, then rinse thoroughly. Water mixed with bleach gives chlorinated water, with the characteristic smell of swimming pools. Diluted to a certain degree, it is not harmful to health. However, I recommend a heavy rinse!
  • Hydrogen peroxide : spray a dilute ready-to-use solution (1 to 3% dilution). Leave on for the recommended time (generally a few hours). Then same pattern as bleach, you rinse, you rinse, you rinse, you smell. And if it smells like a flower , you’re good!


Cleaning the fresh water tank is tedious. It also requires a lot of water, and it is not always possible to have plenty of water when living in a van. This is why the best solution is to opt for a regular, almost monthly cleaning. This prevents the formation of biofilm which requires a lot of elbow grease and rinsing. The other solution is to purify its water upstream of the filling, to avoid having particles in the tank. Also, it is possible to purify the water inside the tank, which prevents the formation of biofilm, the development of bacteria and inhibits viruses. But all that, I explain it here.


Cleaning the grey wastewater tank

Cleaning the grey wastewater tank is a much less critical topic. Because in fact, the only problem with a dirty gray wastewater tank is the smell. The frequency of cleaning therefore depends a lot on what you leave to pass through your pipes and how often you empty the tank. Odors tend to rise more often in the summer and while driving.

If you have odors from the grey wastewater tank while driving but don’t have time or enough water at the moment to clean it, try to plug all the sinkholes before hitting the road!

Since we already have baking soda and vinegar in stock, I opt for this cleaning solution:

  • Drain the tank completely and close the drain valve.
  • You can try to clean the tank by hand by going through the inspection hatch, but it is quite tedious and not necessarily.
  • Pour 1L of white vinegar mixed with baking soda into the pipes.
  • Let several liters of water, cold or hot, flow through your pipes.
  • Roll, let stand a few hours (as long as possible)
  • Drain


And that’s all! The grey wastewater tank does not require more maintenance, since this water is intended for the sewerage system. If you still have issues with the grey water tank smeel, you can use a little bit of bleach. Take care of using the right places to empty this tank if you choose this option.

I just have to wish you good luck!