Distilled vs Deionized Water - Refractometer Calibration

[Alexander1312]

Not technically a reef chemistry question but related.

I am no longer using my RODI water for calibrating my Milwaukee refractometer due to concerns that it might not provide the correct 0 value in the calibration. Since I switched from RODI to Distilled Water, my salinity measurement matches very closely the ICP results, or more specifially, I am always at 35 PSU which is where I want it to be.

I have been using Arrwowhead Distilled Water until now but this seems to be discontinued, so need to look for an alternative source.

Can someone explain what the difference is between Distilled Water and available for purchase lab grade deonized water specifically related to potential salt residue. Does it differ in that regards? Or is the deionized water not better than what I am filtering at home?

 

[PjFish]

Keep a gallon of Niagra distilled near small tanks its 1.49 a gallon at Safeway been using a while no issues

 

[ReyDeFarts]

I have been using Arrwowhead Distilled Water until now but this seems to be discontinued, so need to look for an alternative source.

Should be able to find yourself some distilled water at your grocery store. You can measure it to ensure it is 0 TDS to set your worry aside. I am surprised that Aarowhead would discontinue a product with such an enormous profit margin. Maybe the place you get it at stopped carrying it. But you should be able to get distilled water at grocery stores, Target, WalMart, etc.

You can go through the trouble of getting lab grade deionization water if you feel the necessity to go that route. I'm consistently putting out 0 TDS water at home, now that I upgraded to multiple (three) DI resin chambers. That has been measured through my inline TDS meter and against conductivity/TDS pens that are calibrated to a known 1000 mS/cm standard. I still have distilled water on hand to use for certain tests and to get 0 TDS confirmation when I feel like it.

 

[JVU]

Some thoughts-

1. Distilled water is the gold standard for 0 ppm, not RODI water, so that part makes sense. Reason is that the distillation process results in 100% pure H2O, whereas the RODI process is just very good at cleaning up the water, but not 100%.
2. Stuff that gets through the RO membrane and isn’t ionized will make it into the product water. And also won’t show on the integrated ppm meter. But will show on a refractometer.
3. That said, my RODI unit gives me a reading of 0 ppm. Granted, that is an electrical conduction based estimate so it can miss stuff. I know that it’s not a true 0 because of the above, but it’s pretty close.
4. You can easily check the difference between true-zero and your RODI water by calibrating with distilled then measuring your RODI product water. It will probably still be 0 if you are maintaining your RODI filters.

Bottom line: For accurate calibration, use distilled water. For general use including making up new salt water and top off, RODI is good.

 

[BAYMAC]

Not technically a reef chemistry question but related.

I am no longer using my RODI water for calibrating my Milwaukee refractometer due to concerns that it might not provide the correct 0 value in the calibration. Since I switched from RODI to Distilled Water, my salinity measurement matches very closely the ICP results, or more specifially, I am always at 35 PSU which is where I want it to be.

I have been using Arrwowhead Distilled Water until now but this seems to be discontinued, so need to look for an alternative source.

Can someone explain what the difference is between Distilled Water and available for purchase lab grade deonized water specifically related to potential salt residue. Does it differ in that regards? Or is the deionized water not better than what I am filtering at home?

Distilled has been on and off the shelf since the pandemic. The demand is very high. If I don't get it when they stock it at safeway, I have to wait a few weeks and hope I get there in time.

Both are fine for what you are doing, you won't notice any difference in the range you are testing at.

 

[PjFish]

I used to use Arrowhead distilled also then switched to Niagra when Arrowhead dried up!
Arrowhead was bought by another company plus the U.S Forest Service State officials determined that the company was unlawfully diverting much of the water without valid water rights from public land in the San Bernardino National Forest. They ordered them to stop operations in that area. Not sure if that was the reason or not on their distillation operations..
Distilled water can be a hot ticket lately depending on locations people use them for humidifiers in summer especially in baby rooms/ using to make herbal products or various other uses!
I just talk to a manager at Safeway and order a case takes a couple days then get a call to pick up! I always have a case or two around in case of rodi issues plus I use them on small salt/ freshwater tanks..

 

[Coral reefer]

Sleep apnea machines use it too

 

[JVU]

People also prefer distilled for various obsessive hobby uses like putting a few drops in a glass of whiskey (“cutting”). Refractometer calibration falls in the same category lol. It’s also needed in larger amounts for a wide variety of exacting medical and industrial uses. Lots of uses in the hospital in addition to home use like sinonasal irrigation, humidifiers, CPAP, etc.

RODI works well for our uses. Or a small bottle will last a long time for calibration. We can leave the larger bottles of distilled for those who really need it. Just my opinion.