James,
Most rental DI systems are as follows:
Option #1: 2 mixed bed resin tanks: In this case, a 1 M-Ohm light should be installed on the output of tank #1, before tank #2. When the 1 M-Ohm light indicates that the output of the #1 tank is below 1 M-Ohm, the #2 tank should be put into the #1 position, and a new tank put into the #2 position.
Option #2: 4 mixed bed resin tanks: In this case, a 1 M-Ohm light should be installed on the output of tank #2, before tank #3 & #4. When the 1 M-Ohm light indicates that the output of the #1 and #2 tanks is below 1 M-Ohm, the #3 and #4 tanks should be put into the #1 and #2 positions, and a new tanks put into the #3 & #4 positions.
Rinsing is one of the most important cleaning functions. The quality of the rinse water, in most cases, determines the final cleanliness of the boards.
One more bit of advise... Don't purchase a DI system. All you will be purchasing is a box and some empty tanks. These are no real value! Rent the DI system. Companies like Culligan, US Filter (they own Culligan), and others are by far your best value. Average monthly rental cost for a 4 tank system is $ 80.00 per month with about $ 50.00 tank exchange costs.
Good Luck and Happy New Year!
Mike
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