Chloramine is a disinfectant formed by combining chlorine with ammonia, mainly as monochloramine (NH₂Cl). Many municipal water systems use it because it lasts longer in pipes than free chlorine and forms fewer disinfection by-products. US regulators set a maximum residual disinfectant level of 4 mg/L (as Cl₂) for both chlorine and chloramine in drinking water; typical levels are lower.
In practice
Chloramine is stable. Letting water stand overnight or bubbling it does not remove it meaningfully, which is the key difference from free chlorine. At drinking-water levels its direct effect on cannabis roots is probably small, but growers running living soil or beneficial-microbe reservoirs worry about effects on microbes. Evidence in cannabis is thin (Grower practice concern).
Removal options:
- Ascorbic acid (vitamin C) neutralises chloramine quickly; about 2.5 parts ascorbic acid per part chlorine is a commonly cited ratio (USDA Forest Service), so a pinch per large reservoir is enough.
- Catalytic activated carbon filters.
- RO systems with a catalytic carbon pre-stage.
Find out what your supplier uses from its water-quality report.
Don't confuse with
- Free chlorine: evaporates from standing water within a day or so.
- Chloride: the ion Cl⁻, a micronutrient, not a disinfectant.
Myth check
"Leave tap water out for 24 hours to remove chlorine" does not work for chloramine. Established.
