• You are viewing the forum as a Guest, please login (you can use your Facebook, Twitter, Google or Microsoft account to login) or register using this link: Log in or Sign Up
  • You can now follow UKAPS on Instagram.

Household water softener water usability

MichaelJ

Member
Joined
9 Feb 2021
Messages
60
Location
Minnesota, USA
I have a household water softener system installed in our house. Its one one of those salt-based ones that replaces the calcium and magnesium ions from the city water water (which is considered very hard at around 20 GH) and replaces them with sodium ions - as far as I understand. All for the benefit of avoiding scale and lime buildup, use less soap and detergents etc. - it may release more metals from pipes and joints etc. than hard water. But anyway, the softener is hook up so everything that comes out of the taps run through the system (except for our irrigation system and outdoor hoses). The TDS of the water coming out of the softener (tap) is about 350 ppm, KH is around 10-11, GH “0” (unable to measure with test kit), Ph around 7.5. So if 10-11 KH is about 180 ppm then I assume a large chunk of the remaining 170 ppm (350ppm-180ppm) is from sodium? How much exactly I do not know.

When I restarted the hobby about 9 months ago I was given the advice that I should not be using the straight tap water due to the softener (sodium), but instead get an RO unit and remineralize the RO water to target specific KH,GH values and that is what I’ve been doing since (The RO unit claims 100 GPD and I am getting closer to 56 GPD partly due to being quite a bit lower than the of specified water pressure for 100 GPD…). Years back when I lived in an area with “better” water and no water softener I would just use straight dechlorinated tap water. Simpler times I guess…
Now with two 40 gallon tanks and a weekly 20% WC its been manageable, but I’ve realized recently that my RO water prep approach, fertilization level, bio load and possibly other factors beyond my understanding, that my weekly WC % is probably not enough. I want to up it to 40% a week, at least for a while. It already takes about 6 hours to produce the roughly 14 US gallon of RO water needed for the 20% WCs (7 gallon in each tank which holds a net volume of about 35 gallon ). Not to mention the waste from making the RO water (water is cheap and plentiful here in Minnesota but still…).

So, my question is the following:

Could I instead mix the softened (dechlorinated) tap water with RO water say 65% Tap / 35% RO, which would yield a KH of about 7 and remineralized to target my preferred GH (which is around 8) ?

With this approach I could reduce the time (and waste) to make the RO water by 30% and double my weekly WC %

A rough (and perhaps wrong?) approximation from my rudimentary understanding of the situation: The softener will leave around 45% sodium from the ion exchange which amounts to about 162 ppm for the 20 GH city water, which in turn leaves a residual of about 105 ppm (+ whatever sodium is in the city water already) after being mixed with the RO water (The RO water is 2-3 ppm… which is probably as good as it gets for the money).

Would the residual sodium be or become an issue for the fish or plants? If so, I could of course up the RO ratio, but how much would then be the question?

My livestock are tetras, rams and angles, ottos and mystery snails.
Both tanks are heavily planted with various crypts, various anubias, various swords and some vals.

Cheers,
Michael
 

sparkyweasel

Member
Joined
30 Jun 2011
Messages
1,889
High sodium is generally considered a bad thing.
Could you use the unsoftened tapwater from your outdoor tap mixed with RO? eg; 50/50 to give you 10DGH which will be fine for most fish and plants.
 

MichaelJ

Member
Thread starter
Joined
9 Feb 2021
Messages
60
Location
Minnesota, USA
High sodium is generally considered a bad thing.
That is what I thought, I just have not been able to find some good data points about at what level it becomes a problem.

Could you use the unsoftened tapwater from your outdoor tap mixed with RO? eg; 50/50 to give you 10DGH which will be fine for most fish and plants.
Good point. In the spring, summer and most of the fall I probably could. In the winter its a no-go due to the arctic cold. We winterize and shut off those outdoor taps in the fall to avoid busting the pipes and won't open them again until the spring when we begin gardening etc.

But at least starting in a couple of weeks until the fall, I could just go 50/ 50 and end up with around 5.5 KH and around 10 GH which should be fine. And then I wouldn't have to add any of those pesky chemicals at all, except for dechlorinating the tap water - I will use Prime for that.

Thanks,
Michael
 
Last edited:

ceg4048

Expert/Global Moderator
UKAPS Team
Joined
11 Jul 2007
Messages
9,240
Location
Chicago, USA
Hello,
The resin in your softener can also use Potassium Chloride salt tablets, but is not as efficient and unfortunately, KCL cost around 5X as much as NaCl. Problematic, but still better for the environment and the fish/plants.

Cheers,
 

MichaelJ

Member
Thread starter
Joined
9 Feb 2021
Messages
60
Location
Minnesota, USA
Hello,
The resin in your softener can also use Potassium Chloride salt tablets, but is not as efficient and unfortunately, KCL cost around 5X as much as NaCl. Problematic, but still better for the environment and the fish/plants.

Cheers,

I did not know that. Thanks for the tip! I think I can swing the extra cost as we usually only replenish the softener salt every two months or so. Just looked it up: A 50lb bag of the Diamond Crystal salt I am using now is about $7.5 and the 40lb bag Diamond Crystal Potassium Chloride is $28 (At Menards). Will definitely read up on that.

Cheers,
Michael
 

dw1305

Expert
UKAPS Team
Joined
7 Apr 2008
Messages
11,932
Location
nr Bath
Hi all,
A 50lb bag of the Diamond Crystal salt I am using now is about $7.5 and the 40lb bag Diamond Crystal Potassium Chloride is $28 (At Menards). Will definitely read up on that.
I think that the differential in price (between NaCl and KCl) is smaller in N. America than in Europe. We have <"some threads">.

cheers Darrel
 

ian_m

Global Moderator
UKAPS Team
Joined
25 Jan 2012
Messages
5,222
Location
Eastleigh
Yes softened water with sodium chloride softening has no place in fish keeping (as stated by the long since dead site SkepticalAquarist) due to the presence of sodium ions in the softened water.

Some people use the considerably more expensive potassium chloride to recharge their water softeners, in which case the water can be used in fish tank. Potassium chloride as well as costing up to 5 times as much as much sodium chloride, also needs about 3 times the weight of potassium chloride than sodium chloride (potassium is a heavier ion) to soften the same amount of water.

So US States don't allow sodium chloride water softeners due to the sodium load imposed on their poor sewerage systems.
 

dw1305

Expert
UKAPS Team
Joined
7 Apr 2008
Messages
11,932
Location
nr Bath
Hi all,
I just have not been able to find some good data points about at what level it becomes a problem.
It depends on the fish you keep. As a general rule fish from soft water are much less tolerant of elevated levels of sodium (Na) ions.

If you keep <"Lake Tanganyika cichlids"> they come from very ion rich water with a high sodium content. @MirandaB keeps the "Soda Cichlid" (Alcolapia alcalica) and they would need saltier, more alkaline water again.

cheers Darrel
 

Zeus.

Fertz Calc Meister
Joined
1 Oct 2016
Messages
3,880
Location
Yorkshire,UK
Had a google and.... ''Studies have found that softening water with potassium chloride does not add sodium to drinking water, and will also remove up to 90 percent of the existing sodium from the water''
Good to know also :thumbup:

which could be why it uses the KCl faster as well - 'maybe'
 
Last edited:

MichaelJ

Member
Thread starter
Joined
9 Feb 2021
Messages
60
Location
Minnesota, USA
Hi @ian_m
Yes softened water with sodium chloride softening has no place in fish keeping (as stated by the long since dead site SkepticalAquarist) due to the presence of sodium ions in the softened water.

Some people use the considerably more expensive potassium chloride to recharge their water softeners, in which case the water can be used in fish tank. Potassium chloride as well as costing up to 5 times as much as much sodium chloride, also needs about 3 times the weight of potassium chloride than sodium chloride (potassium is a heavier ion) to soften the same amount of water.
I found a couple of other references to what you mention about KCL vs. NaCL usage and efficiency and trying to understand the implications. For the sake of argument, does that mean for the same amount of KCL I put into the softener I get 1/3rd of the Ca and Mg ion exchange vs. NaCL ? which in turn would raise the dGH of the softened water 3x ?

If so, then to me that sounds like a pretty good tradeoff. Even with the residual Ca Mg we still get most of the household related benefits (lower lime/scale buildup, less soap and detergent usage etc.).

And for the hobby, it more or less gets me to the point where I can use straight dechlorinated tap water, assuming the residual potassium won't harm fish or plant (plants could potentially benefit I suppose).

In any event, this is definitely something I will try over the next couple of days.

So US States don't allow sodium chloride water softeners due to the sodium load imposed on their poor sewerage systems.
True - I used to live in California and new installations got banned there years ago (both NaCL and KCL apparently).

Cheers,
Michael
 

dw1305

Expert
UKAPS Team
Joined
7 Apr 2008
Messages
11,932
Location
nr Bath
Hi all,
I found a couple of other references to what you mention about KCL vs. NaCL usage and efficiency and trying to understand the implications. For the sake of argument, does that mean for the same amount of KCL I put into the softener I get 1/3rd of the Ca and Mg ion exchange vs. NaCL ? which in turn would raise the dGH of the softened water 3x ?
Studies have found that softening water with potassium chloride does not add sodium to drinking water, and will also remove up to 90 percent of the existing sodium from the water
No, it means that the KCl exchanges K+ ions for all three of the cations Na+, Ca++ and Mg++. It is <"Strong Acid Cation Exchange">.

Have a look at the Lenntech Resource <"Ion exchange for dummies">. I've found it really useful.
Also needs about 3 times the weight of potassium chloride than sodium chloride (potassium is a heavier ion) to soften the same amount of water.
Yes, this just due to differing RAMs of sodium (Na) and potassium (K), the anion (Cl-) remains the same, so the difference in RMM is purely from the cation.

NaCl RMM (Na = 23 + Cl = 35.44) = 58.44 g and KCl RMM (39.1 + 35.44) = 74.55 g

cheers Darrel
 

dw1305

Expert
UKAPS Team
Joined
7 Apr 2008
Messages
11,932
Location
nr Bath
Hi all,
Given the huge amount of salt we got through in a year I always thought they had to be a bad idea.
I got fed up with the very restricted life of electric showers etc with our very hard tap water, and I already used rain-water for the tanks and garden, but I was absolutely amazed how much salt we got through when we got an ion exchange unit.

We have a water meter and I should have realised that the harder your water was the more salt you would use, but I hadn't factored in that we actually use a lot more water than we should do.

cheers Darrel
 

Wookii

Member
Joined
13 Nov 2019
Messages
1,805
Location
Nottingham
Although strictly not water softeners, has anyone got any experience with the Template Assisted Crystalisation filters, and how they affect things for aquarium use?

For anyone who doesn’t know what I’m on about:


 

MichaelJ

Member
Thread starter
Joined
9 Feb 2021
Messages
60
Location
Minnesota, USA
Ok, just got around to replacing the Sodium in my water softener with Potassium this: Potassium Chloride Salt Alternative for water softeners | Diamond Crystal® Salt

I paid $22 (USD) per bag (had to get two bags to replace the whole drum) - same brand with sodium is $7...

It is still not clear to me from @dw1305 answer above, if I can expect to to see a raise in GH from the lower effeciency, and if so how much, or if its just that I am going to use more more Potassium relative to Sodium over time?

Will let the thread know how it goes in a couple of days when it's settled in and residual sodium is flushed out out the system.

Cheers,
Michael
 

dw1305

Expert
UKAPS Team
Joined
7 Apr 2008
Messages
11,932
Location
nr Bath
Hi all,
if I can expect to to see a raise in GH from the lower effeciency,...... or if its just that I am going to use more more Potassium relative to Sodium over time?
I don't think there should be a difference in the amount of calcium (Ca++) and magnesium (Mg++) ions replaced, but, you will use more potassium (K), than sodium (Na), for the same weight of salt. Basically 25kg of NaCl has the softening potential of 42.5 kg of KCl. You can ignore the chloride ion Cl-, it is the anion for both salts, so we're only interested in the differential mass of the cation.

A <"mole is always the same amount of atoms"> but the Relative Atomic Mass (RAM) of potassium is higher, meaning that in the same weight of NaCl and KCl, you have fewer potassium ions, only 59% of the amount of sodium ions (23/39.1 = 59%).

cheers Darrel
 

MichaelJ

Member
Thread starter
Joined
9 Feb 2021
Messages
60
Location
Minnesota, USA
Hi @dw1305 Thank you for the clarification!

The potassium have now been in the Softener for about 24 hours (we already went through a lot of water for cooking, showering etc.). I noticed that the TDS is now down in the 260-275 ppm range from yesterdays 325- 350 ppm. dGH is still "0" (unable to measure).

Cheers,
Michael
 

dw1305

Expert
UKAPS Team
Joined
7 Apr 2008
Messages
11,932
Location
nr Bath
Hi all,
noticed that the TDS is now down in the 260-275 ppm range from yesterdays 325- 350 ppm.
Because you have the same no. of ions in both cases (Na+ & K+) the difference may be because some ions are <"better at conducting electricity than others"> (just like a copper wire is a better conductor of electricity than an aluminium wire).

I was expecting to find a straightforward set of values for this, but it looks to be a lot more complicated <"than I'd thought">.

cheers Darrel
 

aeneas

Member
Joined
15 Feb 2021
Messages
60
Location
Slovenia
This thread is of interest to me too. I also have a NaCl based water softener for the entire household. Our tap water is quite ok actually and the water is then softened to 5 Dh and slightly acidic at pH 6.8.
I was plnning to use this directly in a continuous automatic water change system with my new 290gal/1100L discus tank.
But reading this thread I’m realizing this ght not be the best option?! :(
Other thank switching to KCl - are there any other systemic solutions that would make sense?
Or, since I now have a softened tap water coming out directly behind the aquarium - can I install some additional filter at the exit to remove the Na ions?
 

Similar threads

Top