Growing cannabis in a hydroponic system is very rewarding and offers many benefits, such as year-round indoor growing as well as water conservation. Recirculating water throughout a hydroponic system uses less water than watering plants in soil, although eventually, you will need to either dispose of your water or sterilize it to reuse it again.

It is important to know how to properly clean and disinfect your water for reuse or dispose of it correctly to prevent contamination of groundwater.

Do I Have To Change the Water in My Hydroponic System?

Eventually, you will need to replenish the water in your hydroponic system to prevent a buildup of algae, minerals, and bacteria which can damage your system and your plants. Some growers replenish their water when they switch plants to the flowering stage, and others wait to change it only between crops and use the same water throughout the entire cycle. Whichever method you choose, a change to clean water is required eventually.


Can I Throw out My Hydroponic Wastewater?

If you choose to dispose of your wastewater, you should know that you can’t just dump it outside in your garden or pour it down your drain. This would release high concentrations of minerals that can cause damage elsewhere to other ecosystems. You can dilute it with clean water right out of the tap at a one-to-one ratio to dispose of it safely.

You can use this water on self-contained potted plants that will eventually absorb the remaining nutrients, and this also prevents the minerals from entering a wider environment. Some have discarded this diluted wastewater into a compost pile as nitrogen helps the process of decaying compost.

How to Clean Hydroponic Wastewater

If you choose to reuse your water, there are a few methods commonly used to sterilize hydroponic wastewater. Reusing your water promotes environmentally friendly goals of water conservation and minimizes pollution to the environment. There are a few common methods to clean cannabis hydroponic wastewater, although UV treatment is probably the most affordable to the typical home grower. The other two methods to clean the water in your cannabis hydroponic system are pasteurization and ozone sterilization, which may be more affordable to commercial cultivators.


Pasteurization simply means to boil water quickly as it moves between two heat exchangers. This completely sterilizes water to remove algae and bacteria and breaks down minerals reverting it back to zero. Over time, mineral content in the water can damage a pasteurization system, and they can be expensive to buy. This is, however, a completely non-toxic method of sterilizing hydroponic wastewater.

Ozone Sterilization

Ozone sterilization is another effective method to sterilize water. Ozonation occurs with machines that are used to break down oxygen molecules to form ozone molecules which are pumped back into the water. These ozone molecules kill algae and bacteria and also break down minerals.

Ozonation is a very effective, non-toxic method of sterilizing water which also breaks down minerals, although they can be expensive for small operations and require a specialist to set them up.

UV Disinfection

Ultraviolet UV lamps are another method that effectively disinfects water and kills algae and bacteria. UV lamps, however, do not break down minerals in the water like the previously mentioned two methods. UV water treatment systems can be very effective at disinfecting water and are used worldwide to clean water for human consumption and other purposes although another filtration method must be used to remove minerals from the water. UV disinfection is simple and effective.

It is important to keep your entire grow system clean and sterile, and you should periodically clean all parts of your system, including small mechanical parts such as pipes, pumps, and caps, with a peroxide solution. You should also clean and sterilize your substrate, such as Rockwool, which can be cleaned with boiling water and allow it to dry out.

Remember to always grow with high-quality cannabis seeds such as those available from leading cannabis seed breeder Mosca Seeds.

Mosca Seeds is recognized worldwide for high-quality cannabis seeds and stable genetics. We offer more than 15 years of experience and a wide selection of regular, feminized, and autoflower varieties. Check out the Seed Bank now remember to keep your grow space and water clean and sterile throughout your grow cycle.