First of all it is not absolutely necessary to use distilled water. It is a good idea to eliminate one of those variables which are the minerals and contaminates that might be in ordinary tap water. For 30 plus years I use ordinary tap water but it had few minerals in it and never seemed to reduce the life of the batteries.
Kind of a misnomer there.
Distilled water is the best choice. Will tap or well water work, sure will. I never worked in a service shop or dealership that used distilled water for batteries. Most guys never even used a battery filler, just old anti freeze bottles or a hose. Ever wonder why most batteries are now maintenance free, or minimal maintenance?
I worked for a Caterpillar fork lift division for awhile, and the electric trucks had huge 36 volt batteries. And we used distilled water in those - not tap.
On our boats, with 175 pound, hard to get to, expensive group D batteries we use distilled water.
On the golf cart with six expensive 6-volt batteries I use distilled.
On the cheap battery that came with the trailer I use the hose. That has since been replace with 6-volt AGM batteries.
Point is, if you have expensive, quality batteries, distilled water is cheap and proper. Distilled is also proper on the cheap starting batteries used, but the odds are the battery will go bad for other reason before tap water causes an issue.
The proper level is critical now matter what the electrolyte is.
Truckers do it with their 18-wheelers, which are in almost continues service.
Can't compare. OTR trucks could have 2-4 8D batteries, starting batteries, not deep cycle.
We use our trailers in a whole different way.
