DI water, RO water, Softened water ???

[Grizz]

Having read a few posts about fresh water, softened water, DI water, RO water and the like, here’s my 2-cents worth based on years of experience with electroplating and RV fresh water systems.

Softened water: it is not pure and is not mineral free. If you use a salt system, the water it produces will contain salt. I prefer a Potassium based softener system. Softened water contains less minerals than hard water, but will spot because it contains salt (or potassium). Water softened prior to going into a DI tank will make the tank last longer since most of the mineral have been removed.

DI water: (Deionized) is produced by removing the mineral ions through a resin process. It does not remove bacteria, fertilizers, organic matter, etc. It’s not a good idea to drink DI water (or store it) as it is not a purified product. It is good for rinsing your vehicles spot-free and it’s easier and faster to produce that RO water - just run the city water through a DI tank.

RO water: (Revers Osmosis) is purified and safe to drink. It has nothing in it. No chlorine to prevent growth of bacteria. Also, no beneficial minerals! RO water is harder to produce in a coach than DI, but not impossible. The main problem is storage for future use as production is very slow.

DI or RO water should never be stored in your fresh water tank. Only water that has been properly treated with chlorine should be put into and stored in your fresh water tank. Actually, I wouldn’t run non-chlorinated water through any part of my fresh water system. That means any carbon filtration must be at the point of use – not the point of entry.

Some of the posts I read on the subject are quite old. I wonder if the original posters have reconsidered.

FYI: Wikipedia http://en.wikipedia.org/wiki/Deionized_water and others for further detail

[Grizz]

Jack:

That's basically how we did it in electroplating, but ran the RO water from the storage tanks through the DI system before adding it to the plating line. That process greatly reduced the cost of DI since there wasn't much left in the water for the resin to process. Either DI or RO water is good for washing the bus, but not for the fresh water system in a RV.

[dale farley]

What about these small RO systems such as the one in the picture. My bus came with a similar system under the kitchen sink, but someone had removed the filters, so I removed the tank when I got it. I am thinking about getting one for my house to use for drinking water. Of course, these small systems are designed for drinking water only. That's why they come with the faucet. They are advertised to be very effective for small quantities of water.

[jack14r]

I am a mirror manufacturer and the manufacturing process is a chemical plating process,I have had DI and RO machinery,the DI will produce water with almost zero TDS and the RO will remove 98% or greater TDS.I need 10 GPM all day for manufacturing mirrors,the cost to run a RO machine is about 15% of the DI cost but there is always about 3 gallons per minute going down the drain as waste water,there are other cost like salt for the softener and a carbon tank to remove chlorine.I have 2 chemical totes stacked filled with RO water in my shop (550 gallons) that I use to wash the bus and other vehicles,it is as good as DI and cost so much less.RO systems are just too big to haul around in a coach.

[Gil_J]

Jack makes an excellent point on the water wasted in the RO process. In Jack's case, that looks to be about 30%. Unless you can capture and reuse the RO runoff, it doesn't seem like the best use of our water resources unless your water use can't be achieved through any other process.

David's point of salt being transferred to the water after salt based water softening is something I've wondered about. Is the amount of salt of any significance? Take, high blood pressure patience, as an example. They should limit unnecessary salt intake. The water doesn't taste salty, so they aren't taking salt in this case for taste. I have a salt based water softener, as many of us in Florida do.

[jack14r]

Gil,We do return about 2 GPM back through the RO but the net reject is still 3 GPM,there is just too much TDS for our processes to use this reject water in any other places in my plant.Bottled water is usually RO water as stated on the labels,the salt must not be a factor.

[Grizz]

The salt remaining downstream of a salt-based water softener is enough to leave spots when it dries. It is enough to add salt to your human system. However, like a salt water pool (salt to chlorine generator) the salt contained is below the taste level.

Dale: Those small RO systems are great, but they remove beneficial minerals from the water also. A mineral supplement should be taken if you are using RO water for drinking, coffee, tea, etc. A good carbon filter will make your drinking water taste better and not remove the beneficial minerals.

FYI: Follow this link to an article on the differences between salt and potassium softeners. http://www.watertechonline.com/articles/potassium-chloride-as-an-alternate-regenerant