homeburrero wrote:I think what you have there is probably a standard chlorine/chloramine charcoal or carbon block filter. Those will reduce the low level of chlorine to near zero, but will not reduce your chloride at all.


That is more than enough to make your water sensors work. But is likely a little low in alkalinity (alkalinity is a measure of acid-buffering capacity of the water). Most water advice, including the recent SCA water quality handbook, advise that espresso machine water have alkalinity at or above around 40 ppm (in units of CaCO3 equivalence). Your 20-25 ppm RO water with is most likely below that. If some of that 20-25 TDS is comprised of chloride ion, then having good alkalinity numbers is even more important. (Chloride ion can catalyze corrosion in steel and especially in copper/brass boilers and fittings.)

Or better yet, use a drop titration kit to measure your alkalinity. Titration kits that measure 'KH', 'carbonate hardness', or 'temporary hardness' are alkalinity test kits. The API fishcare KH kit that you can buy online or at pet stores is one simple and inexpensive way to do your alkalinity tests.