text: How to Repair a Greenhouse Misting System | DoItYourself.com
  A greenhouse misting system serves two vital functions in your greenhouse: to keep plants adequately watered and to maintain the temperature at a warm but comfortable level, both for the plants and for you. If problems develop with your misting system, it can fail to achieve these objectives. Here are some ways to repair your system for your comfort and for the health of your wild and cultivated plants.
  Step 1 - Identify the Source of the Problem
  Most problems with greenhouse misters occur in the pipes or the misting nozzle. Check the nozzle for correct function. Inspect the pipes for leaks into the plant tables or onto the floor. Check for mold growth that may pinpoint the areas to be searched for less-obvious leaks and drips. Check also for misters that run continuously, and put these on a timer or photosensor to automatically turn them on and off.
  Step 2 - Clean or Replace Misting Nozzles as Needed
  Misting nozzles can become slightly clogged with mineral flakes from water, or can be completely blocked. This results in irregular water flow or no flow at all. If there is a slight blockage, remove the misting nozzle, dip it in a solution of vinegar and water, and reinstall it in the system. Check for correct function. If this does not solve the problem of intermittent water flow, replace it.
  If the nozzle is completely blocked, soak it in a solution of borax, and water for an hour to try to dissolve the blockage. Replace the nozzle if you are unable to clear the block.
  Step 3 - Check and Patch Hoses or Replace
  Examine the hoses at locations of leaks and drips. If the leak or drip is very small, patch the rubber hose with rubber patching compound. If the hose has large holes or splits, replace the hose section. Look for patches of condensation on the pipes that send water to the hoses and misters, as this will mean the room as a whole is too hot.
  If you find that the greenhouse is still too humid, replace the mist nozzles with fog nozzles. These operate at substantially higher pressures (1000 psi) to generate smaller water particles than misters, and cool the air rather than directly dampening the plants.
  Step 4 - Run the Mister Intermittently
  Attach a timer to the mister nozzle system so that it turns the mister on for 5 minutes and off for 15 minutes. Always ensure the mister nozzles are running frequently whenever direct sunlight shines into the greenhouse. This reduces wear and tear on the system as a whole.
  Step 5 - Check the Soil Temperature of Plants
  If after all these checks and repairs, the plants are still not thriving, check their soil temperature. Plants that need very warm soil to grow in will be chilled by greenhouse misting. Avert this problem by installing soil heaters on the plant tray or directly in the plant boxes below the sand layer.