The Caleffi NA570971 is a replenishment bucket of two demineralization resin bags for the Caleffi HYDROFILL NA570912 (6 gpm) portable water treatment filling unit, restoring its ion-exchange capacity for producing low-TDS fill water for closed hydronic systems.
Product data compiled from Caleffi North America technical documentation. Last reviewed July 2026.
Key Features
Restores Demineralization Capacity
Fresh ion-exchange resin recharges the HYDROFILL unit for producing low-conductivity, low-TDS fill water.
Protects Heat Exchangers
Removing hardness minerals prevents lime-scale formation - a leading cause of efficiency loss and heat-exchanger failure.
Targets Under 30 ppm TDS
Average tap water runs about 180 ppm TDS; under 30 ppm is considered ideal for closed hydronic loops.
Stabilizes Glycol Dosing
Consistent demineralized water removes site-water variability for reliable chemical and glycol dosing.
Two-Bag Bucket
Matches the HYDROFILL NA570912 6 gpm unit.
Technical Data
| Function | Filling unit service part |
| Contents | Two replenishment resin bags in plastic bucket with lid |
| For unit | HYDROFILL NA570912, 6 gpm |
| Process | Ion-exchange demineralization (TDS reduction) |
| Target water quality | Under 30 ppm TDS for closed hydronic loops |
Documentation
Technical brochureRelated Products
- Caleffi F59650 Service Part
- Caleffi NA10197 Service Part
- Caleffi NA570974 Service Part
- Caleffi 535051A 3/4 in Auto Fill Valve
Frequently Asked Questions
What is the NA570971 for?
Recharging the Caleffi HYDROFILL NA570912 (6 gpm) portable water treatment unit - it contains two fresh demineralization resin bags in a lidded bucket.
Why demineralize hydronic fill water?
Hardness minerals form lime scale on heat exchangers and aggressive minerals like chlorides attack aluminum, stainless and copper; demineralized water under 30 ppm TDS avoids both and keeps conductivity low.
When should the resin be replaced?
When the unit's output TDS climbs toward 30 ppm - typical tap water starts around 180 ppm, and fresh resin restores full ion-exchange capacity.
- Type:
- Accessory
