I am buying a house that has a water softener which uses salt. Can this water be used for a planted tank?

No, stay away from that.
You will need to add a by pass valve for the softener. This line will be where the softener is installed and then run the water line(Hot and cold) to the tank or a spigit where you can attach a hose for refilling the aquarium.

You never want to water house plants, gardens etc with softener water.
So you should add a by pass!!

It'll cost a bit, but it'll make life much better.
Also, use KCL, not NaCl, it cost more, but is better for you(K+ vs Na+) for various cooking and other things.
Some use that in their softeners but it still causes issues because the amount of KCL is so high relative to what we add for nutrients.


Regards,
Tom Barr

Sorry to bring this up from the dead.

I live in a place that I cannot bypass the softened water (Townhome). Do I just have a long hard road ahead of me? An RO unit was suggested, but I rather not have to go down that road unless I truely have to. I haven't calibrated my test kits (I know, I know ).......

Tap water from a cup that sat out for about 24 hours:
NO3: 5 ppm
PO4: .5 ppm
pH: 8 ppm
gH: 357ppm (26*)
kH: 464 ppm (20*)
(I've always thought we had REALLY hard water)

Tank measurements 2 days out from a 50% water change (EI dosing on a 110 gal.)
NO3: 20 ppm
PO4: 5 ppm
pH: 7.2
gH: 107 ppm (6*)
kH: 438 ppm (24*)
CO2 from Chuck's calc: 45ppm

If you cannot bye pass the water softener R/O is pretty much your only option other than bottled water. On the other hand you may still be able to draw water from outdoor spigots ? HTH. Prof M

So what you're saying is that I'll save myself a lot of greif if I just go RO

Just when I thought I was done building

So I decied to test the water from where it truely comes from (Washing machine). Hmmmmm it's a wee bit different. It didn't sit for 24 hrs though. Does this change any thoughts? Water chemistry is not one of my strong points

NO3 10ppm
PO4 0.5ppm
kH 340ppm (19*)
gH 35.8ppm (2*)
pH 7.6ppm

At the washing machine it should still be passing through the softener. Usually they Bye Pass for exterior hose bibs.

As far as whether to go W/ R/O ? Personally I'd opt for the Bye Pass, but that depends a great deal on your local water quality, and how well you get along with your HOA ??? R/O has it's own inherrent issues to deal with. A high quality industrial water battery will pretty much remove everything, and then you have to reassemble the water as you see fit. This can get tedious as well. We have 4 different sources here all intended for point of service.
Straight tap, Softened, Solid carbon/ceramic matrix, and an Industrial Battery W/DI and, dual R/O. Chemically pure water is actually kind'a Caustic/Corrosive since it is lacking in any or all hardness it's a little hard on stomach lining !