When to add DI Filter to RO System

Water analysis, treatment, and mineral recipes for optimum taste and equipment health.
AMac

#1: Post by AMac »

I plan on continuing to make rpavlis water but want to get away from buying distilled water by the gallon and have no place to buy RO or distilled water in larger/reusable containers, so I am going to install an RO system.

How high does the components on different parts of my tap water need to get before I need to add a deionizing filter to it to get it to an acceptable level of purity for remineralizing?

This is the latest report from one of my tap water suppliers, but the other does not report even these numbers.

Analyte Name Concentration level
ALUMINUM 0.2 MG/L
CHLORIDE 8.27 MG/L
COPPER, FREE 0.010 MG/L
FLUORIDE 0.62 MG/L
IRON 0.20 MG/L
MANGANESE 0.010 MG/L
SILVER 0.00250 MG/L
SULFATE 81.77 MG/L
ZINC 0.010 MG/L
COLOR 10.00 CU
CORROSIVITY -0.09 LANG
ODOR 1.0 TON
PH 8.02 PH
TDS 316.000 MG/L

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homeburrero
Team HB

#2: Post by homeburrero »

AMac wrote:How high does the components on different parts of my tap water need to get before I need to add a deionizing filter to it to get it to an acceptable level of purity for remineralizing?
If properly maintained, an undersink RO system will produce water that is sufficiently pure for use in the rpavlis or other water recipes. To check on that you can just use a typical inexpensive conductivity 'TDS meter'. If your TDS out of the unit reads under appx 20 ppm you can just use it the same as you would use distilled in the your recipe.


If you had extremely hard water with hardness and alkalinity way up in the 500 mg/L (CaCO3 equivalent) range, you would need a conventional sodium exchange softener in the prefiltering stage to protect the membrane, and the water coming through that would have low hardness and high alkalinity, so the final RO water might still have alkalinity up in the 20-30 mg/L range. Nevertheless it would be fine to use in your recipe but you could reduce the amount of bicarbonate in your recipe to allow for that.

In some unusual cases the water out of an RO might benefit by further de-ionization, as with a Zerowater filter. For example if you started out with water that has a chloride ion level of 200 mg/L, then with a 95% rejection by the RO you still would have 10 mg/L in the RO water. If you are very cautious about chloride corrosion you might want to reduce that to near zero via de-ionization.

If buying RO from a kiosk, it may be poorly maintained or may even be blended or remineralized. You can check if it's pure enough with a TDS meter. At my grocery I can select either RO or de-ionized for the same price, so I use the de-ionized (reliably near zero PPM).


AMac wrote:This is the latest report from one of my tap water suppliers, but the other does not report even these numbers.
Can't tell much from that, other than that the chloride level from that water source is nice and low. At that 316 mg/L TDS level, the hardness might easily be well over 200 mg/L (~ 12 gpg). And it's anybody's guess what's in your other water source.


P.S.
You can find a rough guide of typical RO membrane rejection rates for various ions here: http://www.purewaterproducts.com/articl ... tion-rates
Pat
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AMac (original poster)

#3: Post by AMac (original poster) »

Thanks for going through that for me.

I know we have hard water ("Limestone filtered water" is a tagline for most of the major distilleries around here) and constantly changing water, but after your input, I feel comfortable just going with the RO water to remineralize.