Thank you Joanna for your thoughts.
Another type of plastic is polyethylene and that too is used for water tanks.
It is also known to leach chemicals into the water.
Take a look at this company:
They have a great list and descriptions of chemicals to avoid, for your health.
Looks like I will be installing metal water tanks in my van.
This forum stimulates many topics, ideas, and opinions.
It looks like there are many well informed SMB users out there.
And that is great!
The more we each learn and share, the better for all.