Corpus sync: neutrality remakes, note hygiene, datasheet relocation, transformer-split cross-refs
---
title: Domestic Water Softeners and Filtration
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# Treatment Objective {toc}
−## The treatment objective is the first decision the design must resolve, because it determines equipment type, certification basis, and whether the system removes a contaminant or merely conditions the water. {note}
+## The treatment objective is the first decision the design must resolve, because it determines equipment type, certification basis, and whether the system removes a contaminant or merely conditions the water.
## Softening removes hardness ions (calcium and magnesium) by ion exchange; sediment filtration removes turbidity and particulates; carbon filtration reduces chlorine, taste, and odor; RO reduces dissolved solids; and scale conditioning inhibits scale crystallization without removing any ion. These outcomes are not interchangeable. {note}
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step: 5
setpoints:
+ - 5
- 10
- 20
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# Brine and Backwash Discharge {toc}
−## The brine and backwash discharge is both a code item and a coordination item: it must be drained through an air gap, sized for backwash surge, and reconciled with local limits on chloride discharge. {note}
+## The brine and backwash discharge is both a code item and a coordination item: it must be drained through an air gap, sized for backwash surge, and reconciled with local limits on chloride discharge.
## The brine and backwash drain connection shall discharge through an air gap to the receiving drain in accordance with IPC/UPC Table 603.3.1; a direct connection to the drainage system is prohibited.
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```
−# Materials {toc}
+# Treatment-equipment materials are constrained by potable-water certification and by the mechanical service of each component. {note}
−## Treatment-equipment materials are constrained by potable-water certification and by the mechanical service of each component. {note}
+# Resin tanks shall be fiberglass-reinforced or polyethylene-lined pressure vessels rated for the service pressure and certified to NSF/ANSI/CAN 61.
−## Resin tanks shall be fiberglass-reinforced or polyethylene-lined pressure vessels rated for the service pressure and certified to NSF/ANSI/CAN 61.
+# Brine tanks shall be high-density polyethylene with a salt platform or brine-well as applicable.
−## Brine tanks shall be high-density polyethylene with a salt platform or brine-well as applicable.
+# Control valve bodies shall be lead-free brass or engineered polymer certified to NSF/ANSI/CAN 61 and NSF/ANSI 372.
−## Control valve bodies shall be lead-free brass or engineered polymer certified to NSF/ANSI/CAN 61 and NSF/ANSI 372.
+# Ion-exchange resin shall be styrene-divinylbenzene cation-exchange resin conforming to ASTM D2473 and certified to NSF/ANSI/CAN 61.
−## Ion-exchange resin shall be styrene-divinylbenzene cation-exchange resin conforming to ASTM D2473 and certified to NSF/ANSI/CAN 61.
−
```datasheet
label: Resin Tank Material
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- 30-day initial brine salt fill
```