Iron and manganese can foul ion exchange resins, especially if the water contains dissolved oxygen

 Iron and manganese can foul ion exchange resins, especially if the water contains dissolved oxygen. This can happen in water softeners that use ion exchange resins to remove iron and manganese. 

Signs of fouling Decreased effluent quality, Increased rinsing requirements, Sensitivity to flow rate and temperature variations, and Decreased operating capacity. 

How to check for fouling 

Soak a small sample of resin in a 1% hydrochloric acid solution for 5–10 minutes

If the acid solution has more than 5 ppm of iron, the resin is fouled

How to clean fouling

Use a resin cleaner to help control iron build-up 

Use a cleaning reagent that lowers the pH of the resin column 

Use a cleaning reagent that changes the ferric form of iron to the ferrous form 

Use a cleaning reagent that reacts with the iron to form complex compounds 

How to prevent fouling 

Use smaller resin beads, which have a shorter kinetic path through the bead matrix

Use sulfite-based resin cleaners to prevent ferrous iron from converting to ferric iron

Use phosphate sequesters to keep ferric iron soluble