DI is an acronym for “deionized”.  When water passes through DI resin it is considered deionized water.  Different levels of water purity can be attained using DI resin.

Mixed bed resins are a combination of cation in the hydrogen (H) form and anion in the hydroxide form (OH). This is very different from the cation used in softeners, sodium form (Na) and anion used for nitrate, sulfate, tannin reduction, chloride (Cl) form.   

DI water is “hungry water”.  In its purest form it is a solvent anxious to grab minerals and salts.  For this reason, we don’t recommend the use of DI water in a residence.  It will eat the metal pipes, fixtures, and appliances.  We recommend RO, reverse osmosis, drinking water vs. DI water.  Like distilled water, deionized water, can be used in steamers and irons.


Each application requires a different level of water purity.  The deionization process/design can be complicated.  Design is based on the desired endpoint/outcome for each application.  The cost and type of mixed bed resin is different for these various applications.  For instance, you wouldn’t use an expensive, high purity grade mixed bed for spot free rinse or window washing.

Basic Design

At the very least TDS (total dissolved solids) of the water is required to design/supply a simple system for window washing or spot free rinse.  For high purity applications a full cation/anion water analysis is needed.  The more critical the process, the more analysis needed.  TDS meters can run anywhere from $49 to $4900.






When the tanks are exhausted the resin will need to be regenerated at a regeneration facility.  Be sure the facility obeys all municipal, state, and federal waste treatment rules.  Regeneration of dialysis and water for injection applications are governed by 501K rules and regulations

Finally, we recommend getting as much information as possible about a customer’s application prior to quoting.  Applications such as plating and wire EDM will recirculate water through the tanks.  Mixed bed resin will pick up metals.  This resin should not be mixed in or regenerated with resin used for potable water treatment.  It must be kept separate and sent to certified regeneration facilities that don’t put the waste regenerant into the municipal waste system.