On Wed, 27 Jun 2012 09:18:11 -0700 (PDT), "hr(bob) "
wrote:

H2O Yes but the water you use must not had contact with metal source
rain water accumulated on plastic sheets would be Ideal. good luck!

SAY WHAT?!?! *I've been filling them with tap water for decades.

....

You must live in an area with very low mineral content in your water.
Distilled water is the best as it is (supposedly) pure water with
nothing else dissolved in it. Anything dissolved in the water will
upset the battery chemistry.

A good practice. In the 40's -50's, etc. all full service gas stations
filled battery bottles from the spigot. The lady folk always soaked
the plate of the iron in a shallow bath of white vinegar to clean the
steam ports on plate bottom.

In a pinch you can fill a vehicle radiator with creek water.

(I know, I know - hillbilly, redneck, cracker method :-\)