Fresh water system hygiene in your motorhome — the complete guide

Why does the fresh water tank need cleaning and disinfection?

At first glance the tank may look clean, but deposits build up on the inner walls over time. The problem isn't just the tank — it's also the pipes, connections, pump, boiler and taps.

Dirt gets in when filling, via the fill hose, by touching the cap, or because water sits still for a long time. If the system isn't fully drained and dried after use, moisture remains — ideal conditions for micro-organisms.

Extra attention is needed after a long period of standstill. During winter storage, residual water stays in the pipes and tank. Filling with fresh water before the season doesn't mean the interior is clean.

Ordinary rinsing removes loose particles but doesn't disinfect. That's why Iza Effect WATER SYSTEM is recommended: it also reaches pipes, taps, shower and boiler.

What is biofilm and why doesn't water alone remove it?

Biofilm is a layer of micro-organisms and organic matter that clings to the inner surfaces of the tank and pipes. You usually don't see it, because it forms in places you can't reach.

Over time it develops mainly in pipes, connections, against the tank wall and wherever water stands still. It can also occur in the boiler, around the pump, or at the tap outlets.

Filling and draining alone isn't enough: water flows past the surfaces, but the deposits remain. Even clear, odourless water doesn't rule out internal build-up.

WATER SYSTEM is designed to disinfect the water system and helps remove biofilm. The formula contains active oxygen, PAP, silver citrate and stabilisers, and is tested to EN 1040, EN 13727, EN 13624 and EN 14476.

How does WATER SYSTEM treat the whole fresh water system?

WATER SYSTEM isn't just for the tank — it's designed for the hygiene of the complete fresh water system in a motorhome, caravan or camper van.

First fill the tank with clean water, then add the correct amount of product based on the water volume. Always follow the dosage on the packaging.

Switch on the pump and let the solution run through every tap and outlet — kitchen tap, washbasin, shower and any other outlets — until the solution comes out. It's important that the product also reaches the boiler.

Leave to work for at least six hours, then drain the system and rinse with fresh water.

WATER SYSTEM is suitable for plastic and stainless steel. Because it can cause corrosion in some metals, check the materials beforehand and follow the warnings on the label.

When should you use WATER SYSTEM?

Cleaning the fresh water system is especially recommended before the start of the season. If the vehicle has stood idle for months, treat the tank, pipes, boiler and taps before first use.

Treatment also makes sense after a long standstill during the season. If water has sat in the system for weeks, simply topping up isn't enough.

• before a longer trip
• after coming out of winter storage
• if you notice an unusual smell from the water system
• if water has sat in the tank for a long time
• after buying a second-hand motorhome
• if the previous maintenance history is unknown
• before restarting the boiler and shower

How often should you clean your motorhome's water tank?

A fixed rule of thumb helps you not to forget. Disinfect the entire system at least twice a year: when coming out of winter storage in spring, and just before winter storage, so you don't leave contaminated water standing.

If you're on the road all season, a treatment every six to eight weeks is wise — especially in warm weather, since micro-organisms grow considerably faster above 20°C.

In between: drain the tank if the motorhome stands idle for more than a week, and leave the taps open afterwards so the pipes can dry. Standing water is the main cause of a musty smell.

• spring: full disinfection before first use
• peak season: every 6 to 8 weeks
• after any standstill of more than a week: drain the tank
• autumn: disinfect and store the system empty and dry

Musty or rotten-smelling water: what's the cause?

A musty or sulphurous smell from the tap rarely comes from the water itself, but from deposits in the system. In most motorhomes there are three spots to rule out before replacing anything.

The first is the boiler: hot water often sits there for days, which speeds up bacterial growth. The second is the low-lying sections of pipe and the shower hose, where a little water always remains. The third is the fill hose itself — never store it damp and coiled up in a closed cupboard.

If it still smells after a full disinfection and rinse, check whether the smell is coming from the drain rather than the tap. Grey water produces a similar smell and needs a different approach.

• Cleaning the grey water tank and preventing odour
• Six causes of odour in a motorhome

Boiler, filter and water hose: the forgotten parts

The boiler is the part most often skipped. When flushing, also open the hot water taps so the solution replaces the boiler's contents. Don't heat the water during the contact time.

If you have a carbon filter or water filter cartridge, remove it before treatment. Activated carbon binds the disinfectant, reducing its effect and rendering the filter itself unusable. Only fit a new cartridge after rinsing.

Treat the fill hose too: let some of the solution run through it, then store it dry, in a separate bag or box. A hose that has been left lying on the ground introduces fresh contamination into a freshly cleaned tank every time you fill up.

• Water System Cleaner — disinfection of the whole water system
• Water Hygiene Set — tank and water system together

Common mistakes when cleaning the water tank

Most disappointments aren't caused by the product, but by how it's applied. These are the mistakes we see most often.

• Treating only the tank and skipping the pipes, shower and boiler — that's exactly where the build-up is.
• Leaving it to work for too short a time: under six hours, the treatment isn't complete.
• Using household bleach or vinegar. Bleach masks the smell and can damage seals; vinegar doesn't disinfect and doesn't dissolve biofilm.
• Leaving the filter cartridge in during treatment.
• Not rinsing after draining, so the water still tastes of the product.
• Putting the system away filled for winter.

Is the water from a motorhome water tank drinkable?

In the Netherlands and Belgium, the water at most campsites and water points is of drinking-water quality. Quality only deteriorates once it's in your own tank and pipes — so the condition of your system determines whether the water stays safe.

Abroad, this can't be taken for granted. Only fill up at points marked as drinking water, always use your own clean fill hose, and never use the hose that's also used for rinsing the cassette.

A disinfected system and freshly drawn water together form the basis. If you're unsure about the source, use the water for showering and washing up, and bring bottled water to drink.

Key takeaways

The product isn't meant to mask odours — its purpose is the hygiene of the inner surfaces of the tank, pipes, boiler and taps.

• Bacteria, fungi and biofilm can develop in the tank, pipes, taps and boiler.
• Draining or rinsing alone is usually not enough for the whole system.
• WATER SYSTEM disinfects the complete fresh water system, not just the tank.
• Run the solution through every tap and leave it to work for at least six hours.