# Reservoir or root zone water warm (above 23 °C / 73 °F): likely causes and fixes

> Reservoir or root zone water warm (above 23 °C / 73 °F) on cannabis is most often Reservoir or root zone too warm or Pump, timer, air or emitter failure in a hydro, aero or drip system. How to tell them apart, the fix for each and what recovery looks like.

Also called: res too hot, warm reservoir, water temperature high, reservoir temp 26.

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

## Likely causes, most likely first

### Reservoir or root zone too warm (Likely)

- Kind: Root zone; urgency: Act within a day or two
- Fix: Keep solution at 18-22 °C (64-72 °F): insulate and shade the reservoir, move it off the warm floor or away from the light, use a chiller or frozen water bottles in an emergency, avoid submersible pumps that add heat, cool the room.
- Recovery: Solution holds below 22 °C through the light period; new white roots in 3-5 days.
- Confirm: Measure reservoir and root-zone temperature at the end of the light period: Measure the solution in the reservoir and in the root chamber or bucket, at the warmest time of day. Target 18-22 °C (64-72 °F). Above about 23-24 °C (73-75 °F), dissolved oxygen falls and Pythium risk rises; below 16 °C (61 °F) uptake slows.
- Confirm: Dissolved oxygen check: Measure DO with a meter in the root zone, or check the system: air pump running, stones bubbling evenly, return water splashing, no dead spots. Target 6-8+ mg/L. Without a meter: if stones are clogged or the pump is undersized for the volume, assume low DO.
- Article: [Brown roots in hydroponics (DWC, RDWC, NFT): a differential](https://genetixbay.com/knowledge/diagnosis/root-browning-hydro.md)

### Pump, timer, air or emitter failure in a hydro, aero or drip system (Less likely)

- Kind: Root zone; urgency: Act now
- Fix: Restore flow or air immediately: check power, timer, float switches, filters and nozzles. Mist exposed roots by hand or lower plants into solution while you fix it. In HPA and NFT, fit an alarm and a backup pump; roots die fast when misting or flow stops.
- Recovery: Plants regain turgor within hours if roots were not dead; brown, collapsed roots mean rot risk next.
- Confirm: Check pumps, timers, nozzles and drippers: Watch one full cycle: the pump starts on time, every nozzle mists or every dripper delivers, NFT channels have flow end to end, air stones bubble. Clear clogged emitters and filters. In HPA, a failed pump or blocked nozzle can kill exposed roots fast, so check this first when plants on one system wilt together.
- Article: [High-pressure aeroponics (HPA)](https://genetixbay.com/knowledge/systems/hpa-aeroponics.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.