Using food-safe plastic buckets for hydroponic gardening is an important aspect to be considered. If you will ask me, my priority as a hydroponic gardener is the safety of the veggies and herbs I am growing. Nobody wants to get toxins from food, right? That is why choosing the right plastic is essential.
The plastic of which food-safe hydroponics buckets should be made of are high-density polyethylene (HDPE), high-density polyethylene (LDPE), and polypropylene (PP). These types of plastic (better-called resin) are identified by codes 2, 4, and 5 inside the three recycle arrows printed into the plastic bucket.
I know looking for these numbers may sound like an additional task. But it is better safe than sorry, right? To convince you more about how important this added task is, let me enlighten you on the possible risks of not doing this. Let’s go!
Reasons Why You Need to Use Food-Safe Hydroponic Buckets
The use of food-safe (or food-grade) plastic hydroponic buckets is recommended because the exposure of plants to chemicals is a major concern. Traces of bisphenol A (BPA) and phthalates on food are considered a risk in using specific types of plastic buckets for hydroponic practices.
For you to have an idea, bisphenol A (BPA) can easily leach into food and water supplies when exposed to high temperatures. Research has shown that elevating the ambient temperature will also worsen the toxicity of certain compounds. This is the reason why we need to control ambient temperature in hydroponic gardening.
When toxins like bisphenol A (BPA) leach, they can be absorbed by our body. To support this, a study by the Centers for Disease Control and Prevention revealed that approximately 93 percent of urine samples of patients have bisphenol A (BPA) content.
The Food and Drug Administration also noted that bisphenol A (BPA), in small amounts, is safe for the human body. However, continuous exposure can lead to serious health problems according to health and environmental experts.
Moreover, phthalates are also harmful to the body’s endocrine system.
This is the reason why choosing your hydroponic buckets wisely is really important! But aside from the term “food safe”, I bet you have also heard the term “food grade”. Is there a difference between these two terms? Let us know them deeper in the next section!
Food-safe plastic products encompass those that do not present any food safety hazard when they are used as intended. Meanwhile, food-grade plastics pertain to any material that is safe for food handling and production.
The distinguishing factor lies in the intended use. Food-grade plastics are specifically used for handling and producing food.
On the other hand, food-safe plastics are stricter in usage. For instance, if a plastic cup is food-safe for your iced coffee, it does not automatically mean it is safe for your freshly brewed coffee!
Bringing this into our hydroponic world, you should choose a food-safe bucket that can handle even hot temperatures!
At this point, maybe you are wondering. What are those food-safe buckets that can serve as my nutrient water reservoir? Before we dive into that, let us first know what to look for in a food-safe hydroponic bucket!
Resin Identification Code, also known as the resin ID or recycle number, is what gardeners should check for in every plastic container and material considered for hydroponic food production.
You can see these numbers enclosed within a triangle of three arrows and they represent the material used to make those plastic products.
Why is it important to know this? Always remember that not all plastics are food safe! Some of them release toxins when exposed to high temperatures, and we do not want those!
For the next sections, I will enumerate the different resin IDs that are safe for hydroponic gardening and those you need to avoid.
The plastic of which buckets can be made and that are safe are high-density polyethylene (HDPE), high-density polyethylene (LDPE), and polypropylene (PP). These types of plastic (better-called resin) are identified by codes 2, 4, and 5.
Hydroponic buckets with #2 recycle numbers are made of high-density polyethylene (HDPE) and are food-safe. This plastic is usually found in jugs, bottles, and plastic bags.
This plastic is a great food-safe hydroponic bucket material because it can resist corrosion, it does not absorb too much water, and most importantly, it is not prone to chemical leaching.
Low–density polyethylene (LDPE), also known as plastic #4, is a generally safe option for plastic hydroponic buckets. It is commonly used as the main material for bread bags and shrink wraps.
Plastic hydroponic buckets with a recycle number 5 are made of polypropylene (PP) and are food-safe. Yogurt containers and chip bags are the common products with this type of plastic.
Did you know that plastics under this category are microwavable?
I think you are aware that temperature is one of the critical environmental factors in hydroponics. A change in temperature can directly affect your plants!
Thus, with this chemical property—to resist physical change under high temperatures—we can say that polypropylene is a great choice for hydroponic buckets.
Hydroponics buckets made of Polyethylene terephthalate (PET), Polyvinyl chloride (PVC), and Polystyrene should not be used. These plastics are identified by the ID numbers 1, 3, and 6 inside the 3 recycling arrows imprinted in the bucket.
Drinking bottles are usually made of plastic #1 or polyethylene terephthalate (PET). This plastic is not safe due to its health risk of releasing a harmful element —antimony—when exposed to hot temperatures.
You may have seen do-it-yourself videos online where people use recycled bottles as deep water culture (DWC) hydroponic reservoirs.
I think this is the perfect time to remind you to always check the recycle numbers of the bottles you are planning to transform into a hydroponic reservoir. Not all plastic bottles are made of plastic #1, some are made of plastic #3 or plastic #5. Again, always check!
Polyvinyl chloride (PVC) is the common material used in manufacturing pipes. It is not recommended to be used as hydroponic buckets as it was found to possibly contain toxins that can cause serious health issues.
To address this concern, manufacturers have developed a food-safe polyvinyl chloride (PVC), specifically unplasticized polyvinyl chloride (PVC).
Polystyrene, also known as plastic #6, is the major component of styrofoam cups, egg cartons, and cigarettes. Using this on hydroponics is permitted, but extra effort in maintaining a cool temperature is required.
You may be wondering: Why am I seeing deep water culture hydroponic systems made out of styrofoam boxes? Aren’t they made of polystyrene?
Well, hydroponic gardeners who use that have an extra responsibility. They need to maintain a low temperature. Why?
This is because the chemicals in polystyrene can only leach out of the containers when they are exposed to very high temperatures above 80°C. This is also the reason why most hydroponic farms are in greenhouses, as the temperature is easier to control that way.
Learn more about this hydroponic system in our article about deep water culture.
Plastic #7 are other miscellaneous plastics that do not fall under the other resin IDs The danger in these plastics is the presence of bisphenol A (BPA) which is toxic to the body as it affects the endocrine system.
Some products with this type of plastic are lids, medical storage containers, sippy cups, sport water bottles, electronics, and metal food can liners. So always remember not to use these plastic products when you do DIY crafts for hydroponics!
Buckets are usually used in Dutch bucket hydroponic systems.
This hydroponic system is composed of 3 or more buckets connected by a hose. Here, your veggies and herbs sit in buckets. From a nutrient solution reservoir, water is pumped through the hose and dripped over the plant’s base.
From here, the nutrient water flows down the bucket towards a drainage pipe located at the bottom of the series of buckets. The water then goes back to the nutrient solution and the cycle goes on and on.
Do I need food-safe hydroponic net cups?
It is better to use food-safe hydroponic net cups. Net cups are commonly made from high-density polyethylene (plastic #2) and polypropylene (plastic #5), so verify with your garden store before buying them! Learn more about this in our article on choosing your net cups.
How do you make a deep-water hydroponic system?
A deep water culture (DWC) system is made up of a reservoir (bucket), nutrient solution, air pump, and growing medium (clay pebbles). A typical bucket can be transformed into DWC by drilling a hole above the bucket cover that will fit your net cup. Net cups can be made from styrofoam cups. Explore this in our article on how DWC works.
Food-safe hydroponic buckets are highly recommended for food production. If this factor is not considered, health risks are expected. Leaching of toxins like bisphenol A and phthalates can happen when hydroponic systems are exposed to high temperatures above 80°C.
One must look for the Resin Identification Code, also known as resin ID or recycle numbers, to know which plastic products are safe to use in hydroponics.
Plastic products with numbers 2, 4, and 5, are food-safe options; while those with 1, 3, 6, and 7 need to be avoided.
- “Bisphenol A” by National Institute of Environmental Health Sciences in National Institutes of Health.
- “What is BPA, and what are the concerns about BPA?” by Bauer, A.B. in Mayo Foundation for Medical Education and Research
- “Phthalates and Their Impacts on Human Health” by Wang, Y. and Qian, H. in Healthcare 2021
- “Leachate From Expanded Polystyrene Cups Is Toxic to Aquatic Invertebrates (Ceriodaphnia dubia)” by Thaysen, C. et al. in Frontiers
- “Polyolefins, Polyvinyls, and Acrylics” by McKeen, L.W. in Permeability Properties of Plastics and Elastomers (Fourth Edition)
- “Thermal stress and toxicity” by Gordon, C.J. et al. in Comprehensive Physiology