# White scale on pots, pumps, drippers or the meter: likely causes and fixes

> White scale on pots, pumps, drippers or the meter on cannabis is most often Hard, alkaline water pushing pH up over weeks or Cal-Mag overuse (excess calcium and nitrogen). How to tell them apart, the fix for each and what recovery looks like.

Also called: limescale, white deposits on equipment, clogged drippers, scale in reservoir.

Run the checker with this sign: https://genetixbay.com/knowledge/diagnose/?at=roots&s=white-scale-equipment

## Likely causes, most likely first

### Hard, alkaline water pushing pH up over weeks (Possible)

- Kind: Root zone; urgency: Low urgency
- Fix: Alkalinity, not water pH, drives the climb. Above about 100-150 mg/L as CaCO3 (2-3 meq/L), neutralise most of it with acid to an input pH of 5.8-6.2, or blend with RO water. Track runoff pH weekly.
- Recovery: Runoff pH stops climbing over 2-3 weeks.
- Confirm: Get a water report (or test your water): Ask your water utility for the annual report or test well water: alkalinity (mg/L CaCO3), pH, EC, Ca, Mg, Na, Cl, B, and whether it uses chlorine or chloramine. Alkalinity above ~100-150 mg/L as CaCO3 pushes root-zone pH up; sodium above ~50 mg/L and chloride above ~70 mg/L are a problem; softened water is high in sodium.
- Confirm: Measure input pH and root-zone (runoff or reservoir) pH: Calibrate the meter with fresh pH 7 and pH 4 buffers, then measure the mixed feed and the runoff (containers) or reservoir (hydro). Soil and living soil should sit at 6.0-7.0, coco, rockwool and peat mixes at 5.5-6.5, hydro at 5.5-6.2. Track 3+ readings; one reading is not a trend.
- Confirm: Pour-through extraction for container pH and EC: Water normally, wait 30 minutes to 2 hours, pour enough pH-adjusted water on top to collect about 50 mL of leachate (roughly 75 mL for a 15 cm pot, 150 mL for a 4 L pot, 350 mL for 11 L), and measure pH and EC of that 50 mL. Less disruptive than full runoff and more repeatable.
- Article: [Water quality for cannabis: RO vs tap, alkalinity, bicarbonates and chloramine](https://genetixbay.com/knowledge/ph-ec/water-quality.md)

### Cal-Mag overuse (excess calcium and nitrogen) (Less likely)

- Kind: Too much of something; urgency: Low urgency
- Fix: On hard tap water with a complete base feed, stop the Cal-Mag supplement; it adds N and pushes K and Mg out of balance. Use it only for RO or soft water and unbuffered coco. LEDs do not create a Cal-Mag need.
- Recovery: K and Mg symptoms stop spreading within 7-10 days.
- Confirm: Get a water report (or test your water): Ask your water utility for the annual report or test well water: alkalinity (mg/L CaCO3), pH, EC, Ca, Mg, Na, Cl, B, and whether it uses chlorine or chloramine. Alkalinity above ~100-150 mg/L as CaCO3 pushes root-zone pH up; sodium above ~50 mg/L and chloride above ~70 mg/L are a problem; softened water is high in sodium.
- Confirm: Measure runoff EC against input EC: Water to 10-20% runoff, collect the runoff in a clean cup and measure EC of both with a calibrated meter (1.413 mS/cm standard). Runoff more than ~0.5 mS/cm above input means salt build-up; well below input means the plant is hungry or you are over-leaching. In hydro, compare reservoir EC with the EC you mixed.
- Article: [Cal-Mag: what it is, when you need it and when you don't](https://genetixbay.com/knowledge/nutrients/cal-mag.md)

## Note

Guidance, not a guarantee. The checker weighs common causes against what you tell it; confirm with the tests before you treat, change one thing at a time and watch the new growth.