Water softener question...

[tjudy]

I have never had a water softener in a house before... and now I do. I use a lot of RO/DI. My question is this:

What will be harder for the RO/DI to purify (meaning the water that will shorten the life of the membrane and resins fastest), water with a lot of hardness (pre-water softener) or water with a lot of salts (post-water softener?

 

[farm41]

sounds like you have an experiment coming :wink:

 

[tjudy]

LOL.. I really hope to not have to experiment with it! I have been babying this 100gpd membrane for three years now. Backwashing every 100 gallons, fresh micron and carbon every 1000 gallons, and careful checking of water chemistry every batch looking for problems. I change the DI resins as soon as they are completely discolored (about 400 gallons). The result has been a membrane that has lasted three years and (at last count) about 12,480 gallons in three years. The water here in Wisconsin has a LOT more dissolved solids that Colorado or Arizona though. My tap (softened or not) has a 550 mS reading. Carbonate hardness in the unsoftened tap water is a KH of 10! Softened water has a KH of 3. My experience has been that calcium and carbonate hardness are harder on an RO than sodium salts... so I suspect that purifying the softened water will be easier than the unsoftened water. I am looking for confirmation though.

 

[Pnyklr]

What I was told when I had some things serviced in my house:

The water softener only uses the salt to clean out the material in the tank (not the brine tank) when it regenerates. He told me that it was a common misconception that the softener added salt to the water that runs through the house. The salted water only runs through the tank during the regeneration so that the material inside can once again remove the unwanted stuff from the water.

If this is truly the case, then I would say that the softened water would take less work.

EDIT: I found this:

"The idea behind a water softener is simple. The calcium and magnesium ions in the water are replaced with sodium ions. Since sodium does not precipitate out in pipes or react badly with soap, both of the problems of hard water are eliminated. To do the ion replacement, the water in the house runs through a bed of small plastic beads or through a chemical matrix called zeolite. The beads or zeolite are covered with sodium ions. As the water flows past the sodium ions, they swap places with the calcium and magnesium ions. Eventually, the beads or zeolite contain nothing but calcium and magnesium and no sodium, and at this point they stop softening the water. It is then time to regenerate the beads or zeolite.

Regeneration involves soaking the beads or zeolite in a stream of sodium ions. Salt is sodium chloride, so the water softener mixes up a very strong brine solution and flushes it through the zeolite or beads (this is why you load up a water softener with salt). The strong brine displaces all of the calcium and magnesium that has built up in the zeolite or beads and replaces it again with sodium. The remaining brine plus all of the calcium and magnesium is flushed out through a drain pipe. Regeneration can create a lot of salty water, by the way -- something like 25 gallons (95 liters). "

 

[tjudy]

I know that softened water has an elevated sodium content. I can taste it... and test for it. The general concensus (from this and other sites) seem to be what I suspected... softened water (aka sodium water) is easier to purify that calcium carbonate water.