One of your worst nightmares…accidentally filling the water tank with fuel – bad enough if it is your own motorhome, scary if it’s a rental.

But don’t beat yourself up! It happens to people more often than you’d imagine. Luckily all is not lost and before you think about replacing the water tank there’s a very good chance that you can solve the problem quite easily.

We’ve had a number of customers who have faced this predicament. With a little bit of effort, following a simple procedure, you can fix the problem.

We’ve had excellent results with Simple Green Crystal. Crystal is a highly effective, concentrated, all-purpose degreaser and cleaner formulated for critical cleaning applications that demand a fragrance-free solution. Crystal contains a blend of highly effective surfactants that are activated by cold or warm water and is an ideal and effective degreaser/cleaner for such situations. Specially developed for the food and health industries, Crystal is NSF labelled A1, A2, A4, A8, B1 and C1 for use in food processing and handling facilities.

What To Do If You’ve Put Diesel In The Water Tank (Assumes a 46L Water Tank)

First flush the motorhome’s water tank out several times  (use the drain hole or siphon out) and then start as follows: Note: Do not try to empty via the sink/shower taps - you want to avoid getting Diesel in other parts of the system as it will be difficult to remove.

Step One

Pour 4L of Simple Green Crystal into the tank and then fill the tank slowly with water. This will make sure that the solution is well mixed in with water 4 L to 46 L water roughly a 1:10 dilution (note if you can use warm water that’s better - no need to go over 40 degrees C)

Leave for a couple of hours at least then drain out through the drain hole or siphon out.

Simple Green Crystal will foam. Soft water will increase the amount of foam produced. Foaming helps in the cleaning as it can get into hard to reach areas - but also means that it hides when flushing.

Step Two

Flush the tank with water and drain/siphon out.

Step Three

Pour 2L of Simple Green Crystal into the tank and fill the tank slowly with water.

Leave it in for an hour then drain out as in Step 1.

Step Four

Flush the tank with water and drain/siphon out.

Step Five

Fill the tank up to about half way, add 1L of Simple Green Crystal with the contents of the tank and then fill the tank slowly with water. This step saves time in filling the tank with water – you can add the Simple Green Crystal first if you wish

Leave for 30 minutes then drain out as above.

Step 6

Fill the tank with water and drain/siphon until there is no foam left.

This should have done the trick but if not then depending on how bad it is then either do another 1L or go to 0.5L and continue.


And…to avoid using too much, check the water after each flush/drain and between the steps, to see if it has already worked. If so flush and drain until there is no foam left.

Note: Foaming is quite normal with surfactants and detergents and increases with mixing and agitation. For the Flush/Drain sequence it is sometimes best to leave the solution to settle and then slowly drain/flush out followed by a slow tank re-fill and slow drain flush out.


Keeps Your World Clean

Simple Green is the leader in high-quality, environmentally safer cleaning products.

Tough Cleaning - Safe Solutions