Rain vs RO vs distilled water

[sailorboy1]

I can not even imagine how one iwould to find distilled water in a large part of say, the Bahamas. So for the "just run to the store" just let it go.

[captstu]

My battery set up to use a lot of water when I was cruising.

I bet the need by switching my water maker so the Drew from the tank of 450 ppm water better just made.

I then open the test Port and drew off some water until my gauge measured under 100 ppm.

Are use that water to fill the batteries. Probably not as good as the Stillwater but within the specs of the battery.

[Kenomac]

Originally Posted by toddster8

I measure these things for a living. People send me samples from their rooftop collection systems all the time. Rainwater is distilled water.

Not after it's run across a deck, roof or tarp during the collection process, and it also depends on where it's collected. Obviously, you've never tested rainwater in the Mediterranean where it sometimes rains red mud from dust off the Sahara, or near large cities with dust and other pollutants in the air. Are you going to claim that water to be 5-20 ppm and recommend people put it into their batteries?

[thinwater]

PS did a survey of this in August 2015. They also published vendor and industry specs No guessing.

RO Water. If from a tap water fed system, probably very good, but if it is from a seawater fed system this is probably your worse choice, worse than tap water. Just don't.

Rainwater. Very good, unless you did something foolish like collected it from a salty deck or you are in a dust plume. Instead, set out some clean pots. We also sampled rainwater off a hard top (this one was set up with a collection system) after it had rained for 30 minutes. Very good quality.

AC water. Quite variable, depending on the design, but generally not good. Many are designed to evaporate some of the condensate, concentrating the slats.

Dehumidifier water. Generally good. You would think this is the same as AC water, but it is not.

Distilled water. Great... except when you can't get it.

Overall, carefully collected rainwater is probably the most practical choice for a cruiser far from home.

[Web Sailor]

Check w/comedian Steven Wright: "I bought some instant water one time, but I didn't know what to add to it."
Probably be pretty pure if you can solve that problem. ;D

[redpointist]

Originally Posted by Kenomac

Not after it's run across a deck, roof or tarp during the collection process, and it also depends on where it's collected. Obviously, you've never tested rainwater in the Mediterranean where it sometimes rains red mud from dust off the Sahara, or near large cities with dust and other pollutants in the air. Are you going to claim that water to be 5-20 ppm and recommend people put it into their batteries?

There is a difference between suspended dust/sediment and dissolved solids. Even rainwater contaminated with sediment could actually be very low tds, and could be made just fine for battery use by straining the water, or running it through a sediment filter before use.

Unless it was an emergency I would test anything other than distilled water with a tds meter before use in a battery, but you're likely to find rainwater has a much lower tds than seawater fed RO water. Also, dust/sediment is much easier to remove from water than dissolved solids.