How to Build a Compost Tea Maker


Compost tea can be used as a soil drench or a foliar spray. If it is carefully made from high-quality compost, it provides fast-acting nutrients to the plant, and may act to fight diseases. It takes two or three days to make, and it is important that it be used immediately, as soon as it is finished. It must not be stored for future use.

Step 1

Compost tea needs oxygen. Aeration--bubbling air through the mixture to oxygenate it--is absolutely vital in making compost tea. If the tea is not actively oxygenated, it will go anaerobic (no oxygen), start to stink, and will harm your plants. This is why you must use it fresh, and not keep it for even an hour before using it.

Step 2

Half-fill one bucket with the best compost you can find. High-quality compost is essential in making good compost tea. Vermicompost (worm compost) works very well, and many people who use a lot of compost tea keep a worm compost bin just for this purpose. Connect the pump to the gang valve with a 12-inch piece of tubing, then connect the gang valve to all three bubblers with separate pieces of tubing, each 18 inches long. Bury the bubblers deep in the compost, and hang the gang valve over the edge of the bucket. Fill the bucket to within a few inches of the top with water. Connect the pump to an electrical outlet, and turn it on. Add the molasses, and stir well. Reposition the bubblers if necessary so they stay at the bottom of the bucket. Leave the pump running for three days. Stir the mixture two or three times a day, always making sure that the bubblers remain at the bottom of the bucket.

Step 3

After three days, turn the pump off and remove the bubblers. Let the mixture settle for about half an hour, then pour it through the strainer or cheesecloth into the second bucket. Use it immediately. Do not let it sit around for more than an hour or it will start to spoil.

Tips and Warnings

  • Concern has been expressed that the use of molasses and similar additives may support the growth, in the compost tea solution, of human bacterial pathogens, such a E. coli. For more information, read the National Organic Standards Board report linked in Resources. Use the compost tea as soon as it is finished. Do not store it for more than one hour. If you are not ready to use it immediately, add more molasses and keep the pump and bubblers running.

Things You'll Need

  • 2 plastic buckets, 5-gallon
  • Aquarium pump
  • Gang valve
  • 3 bubblers
  • 6 feet of plastic tubing
  • Tubing cutter
  • 1 oz. unsulfured molasses
  • Large wooden spoon
  • Large strainer or cheesecloth


  • National Organic Standards Board, Compost Tea Task Force Report
  • Pennsylvania Department of Environmental Protection, Compost Tea

Who Can Help

  • National Organic Standards Board Report
Keywords: compost tea, compost, vermicompost, worm compost

About this Author

Peter Garnham has been a garden writer since 1989. Garnham is a Master Gardener and a Contributing Editor for "Horticulture" magazine. He speaks at conferences on vegetable, herb, and fruit growing, soil science, grafting, propagation, seeds, and composting. Garnham runs a 42-acre community farm on Long Island, NY.