Posted Sat Sep 18, 2010, 12:31pm Subject: water hardness measuring - adding minerals to RO
Not sure if this is the right place to post this - I searched many, many old threads about water first.
So ... I know I can buy test strips locally (PetSmart for aquariums - or spa stores) - I read about TDM meters but could only find them online.
That got me thinking - a TDM meter works (I read somewhere) by measuring the electrical conductance of the water. Hmmm ... I have a good multimeter. So I experimented using the ohmmeter set to 20M range. Put the probes in an empty cup (in a way that I could repeat their distance and position) and added tap water (reads about .5 MegOhm) - my RO water reads about 2.5 MegOhm. (My RO membrane is very old so I'm not sure how well it still works - but it obviously has less minerals than tap water) I don't really know what this means in terms of any specific hardness value - but it is clear that my tap water conducts more electricity than my RO water. And if I add a pinch of soda - you can clearly see the electrical impedance drop. So at the very least, I could use this method to tell when I've added enough (of whatever mineral I end up adding) to get the RO water closer to tap water hardness. I'm gonna go get some test strips and use them to learn what my meter readings correspond to. Anyone else ever try this? Or is a TDM meter the way to go? Or stick with strips? (or just use tap water and forget about it? hehe)
Anyway --- I was very surprised to discover that my espresso tastes better when I use plain old tap water than when I use RO. But now I've been searching and reading all the old posts I see that this is common knowledge among the serious coffeegeeks.
So ... I'm on a new quest to see what I can learn about getting just the right water balance.
JasonCoffee Senior Member Joined: 17 Mar 2009 Posts: 15 Location: Kansas City Expertise: Professional
Posted Mon Sep 20, 2010, 6:38pm Subject: Re: water hardness measuring - adding minerals to RO
So do you think the waters ability to conduct more electricity makes for a better cup of coffee? Interesting in regards to the tap water tasting better, I always noticed the complete opposite. But then again maybe my tap water is just terrible.
Posted Mon Sep 20, 2010, 7:16pm Subject: Re: water hardness measuring - adding minerals to RO
No, I didn't mean to imply that the waters ability to conduct current would make the coffee taste better. I only meant that it might be a way for me to measure the hardness of the water - since distilled water won't conduct any electricity (no hardness - no minerals at all) but water with mineral content will - and the more minerals the more it conducts.
I'm sure that tap water is completely different depending on where you live.
A problem with hard water is that the minerals get left behind in your boiler (scale) - but the problem with distilled or RO water is that it leaches the metal out of your boiler (and you end up consuming potentially bad metals like aluminum) - and I'm told that it is also acidic. So I guess the holy grail of water is to find water that is perfectly pH neutral and has just the right amount of hardness of minerals that taste good and don't leave scale.
I happen to live in a city with pretty good tasting tap water that is fairly soft. There is a little chlorine taste that I can filter out with a charcoal filter.
Yeah - I was very surprised to find the espresso tasting better with tap water. I've also read that Crystal Geyser bottled water is good and has the right amount of hardness of a type that doesn't scale much. Haven't tried it though.
Chang94598 Senior Member Joined: 24 Oct 2007 Posts: 210 Location: SF Bay Area
Posted Mon Sep 20, 2010, 8:53pm Subject: Re: water hardness measuring - adding minerals to RO
Good tap water generally will make tastier espresso or brewed coffee than RO or deionized water.
The lack of ions will cause the coffee cake to swell, and extend extraction time and bitterness. In ion-exchange softened water, the excessive sodium ions also cause the cellulose in the coffee cake to swell with the same effect. The nerves for the taste buds and smell all require ions to conduct signals properly.
The most recent academic study on the effect of water hardness and ions is found here:
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