Ro Unit Before Or After Water Softener?

[Lakshmi Jagnnathan]

Hello,

I'm in PHX....water is hard^2...we're talking 600-800ppm TDS depending on the time of year.
So, I've used a larger capacity RO unit in the garage to fill up a large container and then pump it into the tank.
I use Seachem Equilibrium to target 7 dGH or so, and also use their alkaline/acid buffers for a kH of 3 and ph of 6.8.

Currently the output of my RO is 10ppm of TDS, but it takes in the water softener output.
With a starting hardness of ~15 grains(roughly), softened water would have about 120ppm of Sodium.
Given my RO is rejecting about 98% of the TDS....it seems like 1-2ppm of that 10ppm is sodium.

What effect(if any) does Sodium have on our planted tanks at 1-2 or even say 5ppm?

I read one article of guy putting his RO before the softener, but I did a whole bunch of other things too....so it wasn't clear to me if his "much better results" were in any way related to the removal of the 1-5ppm of sodium from his tank.

Thanks for your feedback!

Lakshmi

 

[VaughnH]

I recall that people using RO/DI systems say that it is best to start with softened water. Otherwise the filters don't last nearly as long. I can't believe that 1-2 ppm of sodium would have any effect at all on the plants or the fish. After all, we do add sodium bicarbonate to increase the KH, and that will add more sodium than 1-2 ppm.

 

[Lakshmi Jagnnathan]

I recall that people using RO/DI systems say that it is best to start with softened water. Otherwise the filters don't last nearly as long. I can't believe that 1-2 ppm of sodium would have any effect at all on the plants or the fish. After all, we do add sodium bicarbonate to increase the KH, and that will add more sodium than 1-2 ppm.

The ROs do last much longer with softened water....mine is going strong after 4 yrs.....I do periodically do a "flush" of the membranes.

For kH, I'm using the seachem alkaline buffer, is that mostly sodium bicarbonate?

 

[Christophe]

For kH, I'm using the seachem alkaline buffer, is that mostly sodium bicarbonate?

Don't know what Seachem's recipe for alkaline buffer is, but bicarbonate is MUCH cheaper and accomplishes the same thing. Sodium bicarbonate is OK for that, and is dirt cheap at any supermarket. It does add sodium, which is not used so much by plants. Too much sodium can have a downside: https://barrreport.com/articles/sod...ic-macrophytes-volume-2-issue-7-july-2006.19/

If you check around your local brewing / winemaking shops (or online), you can find potassium bicarbonate pretty cheaply also. This gives you your KH boost plus potassium, a primary macronutrient.

Use http://rotalabutterfly.com/nutrient-calculator.php to figure out dosing for the level you want.

 

[Lakshmi Jagnnathan]

Thanks for the feedback.

I checked on Seachem's website....and it says that Seachem's Alkaline buffer is "sodium bicarbonate based", but supposedly has other ingredients(which seachem doesn't divulge).
You need 37.5 grams of it to get kH=3 for 100glns of RO......and with sodium being 274mg per 1gm of NaHCO3, that translates into 27ppm of Na in the water.
This is much higher than then residual 1-5ppm of sodium in the RO water(due to RO unit using softened water as input).

So, keeping the RO unit's input as softened water seems fine.

On the report about NaCl.....it seems to effectively state that plants are tolerant to NaCl to a pretty high degree....even 1000ppm....which is well above anything we'd see in our tanks.
The report states Na is not useful for plants, but Chloride is essential....which brings up a question:

What is the source of Chloride in our tanks and what ppm?

 

[Greggz]

I run 100% RO water. Source is well water then through a softener.

I use MgSO4 and CaSO4 for GH. K2CO3 for KH (like mentioned above, a good source of K).

Readily available and cheaper than any Seachem solution.

 

[toads74]

+1 @Greggz

Post softener + khco3. Used to used Nahco3 but saw a substantial difference in plant growth when I switched. Also briefly tried k2co3 but didn’t like it... too insoulable and left a residue.

Definitely big life extension of the membrane with softened input water. My source gh/kh is around 20d each and would have killed the membrane in a few months, not years.

 

[Lakshmi Jagnnathan]

I believe the main ingredient in Seachem Equilibrium is K2SO4....and I think the Ca and Mg are also in SO4 form. It has a bit of Fe and Mn as well.
The analysis of Equilibrium is attached as a pic.

So, I don't dose any K or Fe...since the Eq already has enough of it...it would seem.