water contamination with auxiliary fuel tanks?

[The motor guy]

This would be awesome to have if they didn't want my right arm and a finger for it. Anyways, I always hear about water contamination on these auxiliary tanks. Look at how the fuel nozzles are mounted. Looks like rain water would go right down the nozzle. I guess it's sealed when you shut it off, but still.

https://elitetruck.com/products/tra...d=120214112464280090&ad_id=120214112469490090