Distilled water plus tap?

February 14th, 2020, 10:29 am

Does anyone mix in a little tap or filtered water in with a larger portion of distilled or reverse osmosis water to cut down on scale/hardness?

#2: Post by **shawndo** » February 14th, 2020, 10:41 am

Yes, I used to do this. It was one of the few times i used high school junior high algebra in real life!
Based on my water hardness (350ppm), it was around 1:4 tap:distilled ratio. so more than just a little.

I stopped once I found the 70/30 water recipe. Definitely prefer adding baking soda/epsom salt over NJ Tap water...

#3: Post by **Nunas** » February 14th, 2020, 11:36 am

Yes, I have a whole house RO drinking-water system with a bypass. It feeds my coffee bar, the kitchen, and all the bathrooms. Currently, it is set to about 25 ppm. I think what you need to do depends on your water. If you have awful water (e.g., lots of chlorine, sulphurous content, iron...), then I suggest you'd be better off just using the straight RO water and adding in a bit of sodium bicarb. There are lots of posts on H-B providing how to do this and many other water "recipes".

February 14th, 2020, 11:43 am

shawndo wrote:It was one of the few times i used high school junior high algebra in real life!

Yes, and if you go beyond TDS when you do your algebra you might get a perfectly good water. For example, calculate your dilution so that you have ballpark 40 mg/L alkalinity, then calculate the hardness at that dilution to see if it may be too hard and scale prone. Then if you have significant chloride (talking chloride here and not chlorine) calculate the chloride in your diluted water and make sure it's nice and low (below 15 mg/L if you want to be cautious about corrosion.)

Here's an example of how you might calculate that:

Given tap water:
hardness (GH) = 180 mg/L as CaCO3 (10 °dTH)
alkalinity (KH) = 120 mg/L as CaCO3 (6.7 °dKH)
chloride 60 mg/L as ion

1. Calculate dilution needed to get 40 mg/L alkalinity
40/120 = 0.33 which means 33% tap and 67% distilled, or 1 part tap to 2 parts distilled

2. Calculate hardness of your dilution
180 * 0.33 = 59 mg/L as CaCO3
(Not bad, might scale a little in a hot steam boiler, and is in the recommended old SCAA ideal ballpark for hardness.)

3. Calculate chloride of your dilution
60 * 0.33 = 20 mg/L
(Is below the LaMarzocco recommendation for chloride ion, but above the Synesso recommendation of 15 mg/L, so you might prefer using mineral salts to remineralize your distilled rather than using your tap water to do that.)

P.S.
To take care of chlorine, chloramine, off tastes and odors be sure to run your tap through a charcoal or a carbon block filter.

#5: Post by **daveR1** » February 14th, 2020, 6:50 pm

My tap water is very tasty but quite hard. I mix 30% tap + 70% purified & the resultant mix pretty much hits the SCA water recommendations. I test the water occasionally as I've noticed the tap water hardness varies throughout the year, so I adjust the mix.