The never-overflowing wash tank.

If you mist wash or spray wash your biodiesel, you may become bored with having to stand near the tank, keeping an eye on the level, so it doesn't overflow.

This simple layout automatically keeps the level in the tank fixed. As you add water via a spray or mist head, it passes through the biodiesel, taking methanol, soap and glycerol with it, and then collects in the bottom of the tank, where it is forced up, by the weight of biodiesel on top of it, through a drain pipe, to drain off as much water as is added.

It is arranged in a way which prevents it from siphoning uncontrollably.

The never overflowing biodiesel wash tank

The biodiesel outlet tube on the left is bent over with a U joint, to prevent water from entering the biodiesel drain pipe during washing.

Fill the tank with water first, to about 1/2 way between the biodiesel drain tube and the bottom of the tank. This should be around 15% of the tank capacity.

Caution: This system will work so long as the wash water can freely pass through the drain tube. Therefore, do not use this system in winter, where freezing of either the biodiesel or the water may occur. Use a large bore drain pipe to minimise the risk of it becoming blocked with a leaf, fat spider etc!

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Graham Laming