RO vs Distilled

[kavakava]

I'm aware that distilled water is recommended for topping off wet cell batteries. However, since we have a Reverse Osmosis system in the house, can the RO water be used too? Thanks.

[Cruisingdad]

That is a good question.

It is likely that distilled water is probably more "pure" water than RO, but by the simple process of a well running RO, I can't help but wonder if it would be fine too?

To te best of my knowledge...

In Cape Coral, much of their water is made from RO (I think they use brackish water/sea water). After they are finished, the water coming out is so pure that they mix back in 15% (I believe it is 15%) of the mineral wash they just took out. This gives the water a better taste (or a taste at all) and slows down erosion (pure RO has no dissolved minerals and thus has not reached any saturation point).

The question is how pure your RO water is?

In labs, we would always use distilled water... but I wonder if that is only because of the availability and cost. My guess is still that distilled is more pure (by the nature of how it is made), but RO would be a close second.

I would say yes... you could. But unless you used a GC or HPLC to measure the TDS and contaminants, you could not be sure. Still, at .60-$1 gallon, is it worth it??

You have to decide that.

- CD

[Canibul]

pure water does not conduct electricity. If you put a volt/ohm meters leads in your RO water, and can measure any appreciable resistance, whatever is conducting that electricity will start to work on your batteries. Probably a matter of degree how much faster RO water would degrade the batteries. Maybe none at all...hopefully.

[camaraderie]

I would use only distilled...all the boat made RO water I've ever had has a taste to it that can only be from imputities. How about a test, buy sme distilled and take some of your RO and taste test them. If you can taste the difference there are impurities. ...safe to drink but I'd not use it in my batteries.

[dakuehn]

Much of the purity of RO depends on the post filtration employed. Barebones RO filtration just using a prefilter and Thin Film Composite (TFC) membrane can yield water @ 95 % pure. Post filtration with resins (there are many combinations) can get you to 99.9%. In the world of aquarium husbandry we avoid distilled water because this can be done in copper tanks, which can result in toxic ppm concentrations of free copper

[Cruisingdad]

It is an interesting thought though Cam, makes me wonder:

What of you RO and charcoal filter? I mean, at what point are the impurities so small it does not matter? I seriously doubt (can almost guarantee) that Kroger's distilled water is without impurities.

You live in the Abacos, or S America, or whatever... and need to top off your batts... why not use RO and filter? It is probably better than the distilled you get down there (if you can get at all). Brings up a interesting conversation.

How pure does your water really have to be?

Here in the states, you can run up to any grocery store and buy it for pennies... so why not use it? But as we try to set up our boats to be more self sufficient, why couldn't you RO and filter? Would it REALLY make that much (or any) difference????

[sailingdog]

I guess a lot of it depends on what impurities are in the RO water. Certain impurities aren't really going to affect the chemical reactions that need to take place in a battery, others will. Some salts will combine with the electrolyte and effectively reduce the quality of the electrolyte, others will not. I would highly recommend that you use distilled water if you can get it. There isn't a lot of water needed for a properly designed battery system.