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dkindle 04-09-2011 12:29 PM

Softened Tap Water Safe for Concrete Mixing?
Hopefully this is a stupid question, but my garden hose is not plumbed behind the water softener, but rather the water that comes from the spicket is softened just like the rest of the water in the house. I have been mixing concrete for new porch footers and it just dawned on me that salt + concrete = BAD. I have read that water softened with salt has a really low concentration of sodium, otherwise we would all have high blood pressure due to salt and it wouldn't be safe. Someone please tell me I have nothing to worry about and don't have to break up my footers! Thanks.

Jackofall1 04-09-2011 12:39 PM

Hello and welcome Dkindle, to the best darn DIY'r site on the web.

You will be fine, water softners don't actually make water salty, the salt brine is used in a chemical reaction to change the electrical charge on the media in the resin tank during the flush cycle to remove the collected minerals.

No worries mate!


dkindle 04-09-2011 01:15 PM

Thanks for the quick reply. I put up some concrete blocks using the same water a couple of years ago and they are still holding strong, but I thought it wouldn't hurt to ask. Thanks again.

Daniel Holzman 04-09-2011 02:16 PM

I took this from the web site How Things Work.

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 prec*ipitate 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.

This paragraph seems to state very clearly that the magnesium and calcium ions in the water are REPLACED with sodium ions, which is what I thought happened. Therefore the water in your house actually does end up salty, however the concentration may be low, it would depend on the concentration of magnesium and calcium ions in your incoming water. As a note, calcium and magnesium are +2 ionization, sodium is +1, so you will replace each calcium and magnesium ion with 2 sodium ions, so the concentration of sodium will be twice that of the incoming water if you get 100 percent replacement.

As to whether the concentration is bad for concrete, well normally you want to mix concrete using water with no sodium, so it may be a bad idea to use softened water for concrete. Perhaps a concrete mixing expert can chime in.

jomama45 04-09-2011 02:24 PM

Seeing as you're only mixing concrete for your porch footings, I don't think you'll be even remotely close to compromising enough strength from the concrete to make any noticeable difference. Acceptable soil bearing capacity is generally a fraction of comprehensive concrete strength, making the soil the weak point in most situations. I'll see ,if I can remember, to ask one of the quality control guys we deal with if they have any experience in breaking test cylinders with soft water vs. non-softened water.

stadry 04-09-2011 03:19 PM

took this from our most recent GaDOT & USNavy specs - ' POTABLE water ' :thumbsup: of course everyone knows the Corps of Engineers & the Air Force're ' different ' :laughing:

concretemasonry 04-09-2011 03:26 PM

itsreallyconcrete hit it right!!

The big word is potable for anything but the most critical needs. If you can drink it, it will work to make the cement hydrate.

Have seen some visually bad water used for concrete. Even the few minnows were lost/destroyed in the mixing without any problems in meeting the needs. It was good sound aggregate, so a few minnows did little to increase the amount of organics up beyond what is allowed in the aggregate spec.


stadry 04-11-2011 05:10 PM

minnows still have a very high compressive strength :eek: back in the day, wasn't unusual to find pcs of wood in conc that was broken off storage bins, remember ? :yes:

Wildie 04-11-2011 08:49 PM

Perhaps you should consider removing the outside tap from the softened water supply.
I doubt that you would need softened water for the grass.
I'm of the impression that softened water should only be used for washing (bathing, clothes,dishes)purposes only.
If your whole house is on the softener it will certainly consume cost more to run it.

MarkWei 04-25-2011 12:00 PM

Was lurking, saw this thread, and thought I'd chime in with another quote:


A water softener works by exchanging ions. It pumps water through it and transfers sodium into the water, removing the calcium and magnesium. This makes it softer.

from how water softeners work

hope that helps, cheers! :)

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