Put a small box of Bi-carb Soda in your water tank half to 3/4 full take the van for a spin and you should be right again Keith

Cheers John

By the time you get the town water to your tap, there in not much chlorine left and what is growing in the tank could just keep growing.
Give the tank a dose of household bleach (non perfumed, clear) each week or 2.
Use about 10-20 ml per 100 litres of water. More would be better for a while.

If your filter is a decent one (1um active carbon) and is fitted in the pipe after the van pump and just before the kitchen tap, it will remove any chlorine left in the water, but the quantities I mentioned probably won't be noticed.

Cheers,
Peter