Reef calculator

RO/DI Output Calculator

A 75 GPD membrane rarely makes 75 GPD. See what yours makes, and how long a batch takes.

gal

How this works

Membranes are rated at 60 psi and 77°F. Output scales with net pressure (water pressure minus about 1 psi per 100 ppm TDS) and drops about 3 percent per °F below 77°F.

RO/DI Output

Questions

When do I change my DI resin?

When the TDS meter after the DI reads above 0.

How often should I replace the membrane?

When TDS after the membrane climbs to about 10 percent of tap TDS, usually every 2 to 3 years.

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