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Estimating DI Resin Running Cost from Actual Water Throughput

Calculate DI resin cost per acceptable litre using actual throughput, consistent changeout criteria and representative service intervals.

Updated · NANOLAB Knowledge

The useful cost of a deionization cartridge is its cost per acceptable litre delivered, not simply its purchase price. Track throughput until the supplier's defined changeout point, then compare cartridges under similar incoming water and operating conditions.

Calculate a real service interval

In an illustrative example, a cartridge costs 90 currency units and provides 1,800 acceptable litres before scheduled replacement. Its media cost is 0.05 per litre. If another interval provides only 1,200 litres, the cost becomes 0.075 per litre.

Those figures exclude equipment, labour, water and disposal or service charges. State which costs are included. Do not call a media-only calculation the total cost of water treatment.

Keep the endpoint consistent

Define acceptable output using the equipment supplier's method. Running one cartridge past the specified endpoint makes it look cheaper while delivering a different service. Record the outlet readings, volume counter and replacement reason.

Incoming water also matters. A seasonal supply change or a different mobile job location can change media demand. A shorter interval is not automatically evidence that the new cartridge was defective.

Avoid false precision in forecasts

Use several representative service intervals to build a planning range. If records are limited, label the estimate provisional. Do not extrapolate from the first few litres of a new cartridge or from a single unusually quiet week.

For example, planning around a range of 1,200–1,800 litres is more honest than promising exactly 1,650 litres when feed conditions vary. Keep a replacement arrangement that prevents jobs from depending on the last theoretical litre.

This calculation helps decide whether additional pretreatment or a different system merits investigation. It does not replace supplier sizing or authorize operating exhausted resin beyond its specified limit. The objective is consistent rinse quality at a known operating cost.

Related guidance

Technical references: Ecolab Purolite: Mixed-bed ion-exchange resins.

For product-specific application instructions, consult NANOLAB technical documentation or ask about your surface and intended use.