1.1.2 DI filters
Description
This article is from the ReefKeepers FAQ, by several authors (see the Credits section).
1.1.2 DI filters
De-ionization (DI) units come in two basic varieties: mixed bed and
separate bed. Two chambers are used in separate bed units, one
for anion resins (to filter negatively charged ions), the other
for cation resins (to filter positively charged ions). Mixed bed
units use a single chamber with a mix of anion and cation resins.
DI units are 100% water efficient with no waste water. They are
typically rated in terms of grains of capacity (a grain is 0.065
grams). Once the capacity of the unit is reached it either needs
to be replaced or recharged (using strong acids and bases).
Recharging is normally only an option for separate bed units.
A quick check of the local water quality charts (normally
available free from the water supply company) will reveal the
water purification capacity of a given DI unit. For example, if a
unit rated at 1000 grains is purchased and the local water supply
has a hardness of 123 mg/l (Missouri River, USA), then the unit
capacity is (1000*0.065)/0.123 = 528 liters = 139.5 gallons of
purified water.
Water production rates for DI units varies, but is typically
around 10-15 gallons/hour.
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