Spring awakening for your water system in yacht and camper

Published on 7 May 2025

The first warm sunshine says it all: the 2025 camping and boating season is ready to start! Anticipation for freedom and adventure is growing. But before you cast off the lines or start the engine, it is worth taking a critical, often underestimated part of your mobile home under close scrutiny: the water system.

After the long winter break, during which your motorhome or boat may have stood unused, invisible lodgers may have settled into tanks and pipes. Residual water, temperature fluctuations and darkness provide ideal conditions for germs, bacteria and stubborn biofilm to form. These can not only spoil the enjoyment of fresh water but also pose a serious health risk.

The invisible danger of hibernation: how biofilm conquers your water system
After a long period of standing still, as is typical over the winter months, small amounts of residual water often remain in the fresh water tank, the pipes, the pump or the boiler. Even if you have "emptied" the system, moisture and tiny pools of water remain in many places. This residual moisture, combined with the often considerable temperature swings between cold nights and the first mild spring days (which lead to condensation forming on the inner tank walls), creates an ideal microclimate for the growth of microorganisms.

On the inner surfaces of the tanks and hoses (which, depending on material and age, can also have micropores or rougher patches where germs settle more easily), naturally occurring water bacteria, but also germs introduced from outside, now begin to establish themselves. They feed on tiny organic particles in the water or on substances that can leach out of the material of the pipes themselves.

These microorganisms, including bacteria such as E. coli (an indicator of faecal contamination, if, for example, contamination was introduced while filling), pseudomonads (typical moisture-loving germs that thrive in standing water and can trigger infections), or the feared Legionella, multiply and, in doing so, excrete slimy substances. These substances, known as extracellular polymeric substances (EPS), form a protective coating and are the basis of the biofilm.

A biofilm is therefore far more than just a bit of dirt; it is a complex, structured community of microorganisms embedded in a self-produced slime matrix. This matrix effectively protects the germs from outside influences, such as brief temperature fluctuations or simply flushing with water. The biofilm grows over time, becoming thicker and more complex, and can narrow entire pipe cross-sections. It often remains unnoticed for a long time, as it develops out of sight.

Health risks and quality defects: the consequences of a contaminated water system

An established biofilm is a constant source of contamination for the entire water system. Every time water is drawn, germs and parts of the biofilm can get into the fresh water.
The health risks involved should not be underestimated:

1. Pseudomonas aeruginosa, a common biofilm former, can cause infections on contact with skin or mucous membranes, especially where there are small wounds. Ear and eye infections are also possible.
2. Escherichia coli (E. coli) can cause severe gastrointestinal illness with diarrhoea and vomiting.
3. Legionella (Legionella pneumophila) are particularly treacherous, as they can enter the lungs by inhaling the finest water droplets (aerosols), such as those produced when showering or through atomisation at taps, and can trigger Legionnaires' disease (a severe pneumonia) or the milder Pontiac fever.
4. Enterococci can also occur in biofilm and cause urinary tract infections or other infections. Besides these direct health hazards, a contaminated system also leads to a considerable reduction in water quality. The water can take on a musty, earthy or foul smell and taste, making it impossible to enjoy drinks or prepare food. Visible slime particles in the water or discoloured outlets on the fittings can be late signs of severe biofilm infestation.

Why simple rinsing or household remedies can fail against biofilm

1. Many vehicle owners simply try to flush their water system vigorously with fresh water at the start of the season, or turn to household remedies. But the reality is sobering: an established biofilm is extremely resilient. The slime matrix acts like protective armour and a diffusion barrier.

2. Mechanical cleaning (rinsing): often only removes loose particles and the uppermost, easily accessible layers of the biofilm. The firmly anchored base, and the microorganisms protected within it, mostly remain untouched, however, and can quickly spread again from there. This is referred to as the "seed material" for rapid recolonisation.

3. Hot water: would need to reach temperatures of over 70°C for an extended period throughout the entire system (including all "cold corners") to show any effect, which is barely practicable or material-friendly to achieve in most leisure vehicles.
4. Household cleaners (e.g. vinegar cleaner, denture cleaner): are often not sufficiently biocidal against the variety of germs in the biofilm, or can attack materials and themselves leave residues that can in turn serve as a breeding ground.

The biostream® ZERO solution helps: putting an end to biofilm professionally

For a truly thorough and permanently effective cleaning and disinfection of your water system at the start of the season, we recommend using biostream® ZERO. This highly effective, chlorine-dioxide-based disinfection concentrate was specially developed to fight even stubborn biofilm effectively. The disinfection process is very simple:

1. Activating biostream® ZERO (example: 250 ml bottle):
   Using it is as simple as it gets. The supplied tablet or powder is added completely to the liquid component in the bottle. Shaking or stirring dissolves the activator. Then leave the solution to stand for at least 3 hours at room temperature until it has taken on a clearly yellowish colour, a sign that the chlorine dioxide concentrate is ready for use. Important before using it in the system: any water filters present must be removed or bypassed for the disinfection process. Likewise, any permanently installed appliance cooling or UV disinfection units must be switched off, as these could impair the effect of the disinfectant or be damaged themselves.
2. The power of chlorine dioxide (ClO₂):
   The active substance chlorine dioxide contained in biostream® ZERO is an extremely effective biocide. Unlike simple chlorine, it does not form harmful chlorinated organic compounds such as trihalomethanes (THM) and attacks the slime matrix of the biofilm directly. Chlorine dioxide is a small, uncharged molecule that can penetrate the polymeric structure of the biofilm and destroy the microorganisms embedded within it through oxidation. It works not only on the surface but penetrates deep into the biofilm and dissolves it from the ground up. Scientific tests, for example carried out by the University of Hannover, confirm the high efficacy of biostream® ZERO against relevant germs such as E. coli, Pseudomonas aeruginosa and Enterococcus faecium, even at low concentrations and short contact times (a reduction of at least 99.9 % was demonstrated). According to DVGW code of practice W 291, biostream® ZERO is also around 25 times stronger than hydrogen peroxide, which is often considered only a weak oxidising agent and does not reliably remove biofilm.

Step-by-step guide to spring disinfection of your water system with biostream® ZERO:

Careful preparation and execution are the key to success. Allow yourself enough time for the disinfection.

1. Preparing the system:
   Check all accessible components of your water system (tank, hoses, connections, taps) for visible dirt or damage.
2. Drain the entire system completely, including the boiler/water heater. Open all taps and drain valves to do this.
3. Make sure to remove all water filters (pre-filters, activated carbon filters, etc.) from the system, or ensure they are bypassed. Disinfectants can damage filter media, or lose their effect.
4. Switch off any UV lamps for water disinfection or the cooling of water dispensers, if present.
   
5. Activating biostream® ZERO:
   Prepare the biostream® ZERO concentrate as described above (tablet/powder in liquid, 3 hours reaction time until it turns yellow).
6. Dosage for the basic sanitation (recommended at the start of the season or in cases of heavy contamination/suspected biofilm):
   For an intensive basic disinfection, especially where biofilm might be present, use 10 ml of the freshly activated biostream® ZERO concentrate per 1 litre of water that your entire system can hold (tank volume plus the estimated volume of the pipes and the boiler).
   Add the calculated amount of biostream® ZERO concentrate to the empty fresh water tank.
   Then slowly fill the tank with fresh tap water until it is completely full.
   Now open all taps (cold and hot water) one after another until the yellowish disinfection solution visibly emerges. This ensures the solution has reached the entire pipe system, including the boiler. Then close the taps again.
7. Contact time: leave the biostream® ZERO solution to work throughout the whole system for at least 1 hour. Longer contact times, for example several hours or overnight (up to 12 hours is possible), can further improve the effect against stubborn biofilm.
8. First rinse: once the contact time has elapsed, drain the entire system completely again via all drain valves and taps.
9. Second application (crucial for biofilm!):
   To ensure the biofilm is not just attacked on the surface but is effectively destabilised and completely removed, a second application is essential. A single application where heavy biofilm infestation is suspected can, paradoxically, lead to a short-term worsening of water quality at first, because the biofilm is merely broken up and dissolved particles enter the water.
   So repeat step 9: dose a further 10 ml of activated biostream® ZERO concentrate per litre of system volume, fill the system and again leave the solution to work for at least 1 hour.
   Final, thorough rinse: after the second contact time, drain the system completely once more. Then rinse the entire system thoroughly at least two to three times with plenty of fresh drinking water, until no yellowish colour or any slight odour of the disinfection solution can be detected at the outlets any longer.

Order biostream® ZERO now