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re: Water softeners, very hard water

Daniel Segel wrote:

> I recently moved back to a place with very hard water - the 1999 Water 
> Quality Report lists the weighted average hardness, as CaCO3 at 439. They 
> also state "water hardness ranged from 130 mg/L to 680 mg/L (7.6 
> grains/gallon to 39.7 grains/gallon). To assist residents in adjusting 
> water softeners, the average hardness was 25.7 grains per gallon."

> I'm getting ready to set up my aquarium again and have a few questions 
> about this:

> 1. What do all these #'s mean? I know it's really hard based on what I've 
> read, but beyond that I'm at a loss. What exactly are they measuring when 
> they say things like "130mg/L"?

You can think of this as the amount of calcium carbonate dissolved in
the water.  That isn't what it is, but usually that's close.  Maybe
someone else will go into more detail.  The values in mg/l and in grains
per gallon both measure the same thing using different units.  The wide
range in numbers -- 130 to 680 mg/l or 7.6 to 39.7 grains per gallon
means that your water supply is extremely variable.  It could be a
variation from place to place within the water system, it could be a
variation over time or it could be both.  You should probably get a
hardness test kit and measure yours so that you know what it is.

> 2. Everybody in town has water softeners installed, but they're usually not 
> connected to the cold water tap in the kitchen, or to the outdoor spigots. 
> But if I use either of those sources for water changes (or to initially 
> fill the aquarium) then I have no choice but to use fairly cold water (if I 
> include a little warm water then it's been softened.) So, is the softened 
> water dangerous for plants or fish? The water softeners all require salt to 
> be added on a regular basis, and I always assumed that was going into the 
> water. I haven't actually tested any parameters of the softened water yet. 
> When I was growing up my Mom used to tell me that the softened water was 
> bad for plants and that I shouldn't drink it, but I never asked why...

Water softened with an ion-exchange water softener (the kind recharged
with salt) is bad for plants and planted aquariums.  The hardness that
they remove consists of calcium and magnesium, both of which are
essential for plant growth.  The softener replaces those elements with
sodium, leaving a lot of sodium in the water and rather little calcium
and magnesium.  The high sodium concentration can effectively block your
plants' ability to use the little calcium and magnesium that is left.

Softened water can be *really* bad to use on outdoor plants, because it
can destroy the texture of the soil and cause drainage problems.  The
softened water is also more saline than unsoftened water.

Problems are likely only if you use pure softened water.  A mix of hard
and softened water can probably be used without problems.  There's no
firm number I know of for how much hardness you will need in the mixed
result, but I'll guess that you can can prevent problems by keeping at
least 70 mg/l, or about 4 degress hardness in the mix.

Roger Miller