Invisible Risks In Your Spray Solution – Why You Might Be Applying Heavy Metals to Your Crop

{sponsored} Cannabis growers are subject to more product testing than other horticultural crops. This is for good reason, since consumers will ingest and inhale the product, often for health and wellness benefits. As more states bring metals testing online, growers are learning to avoid use of products that may elevate heavy metals in the crop. However, did you know that your most valued grower tool, your spray equipment, has the potential to contribute heavy metals in your cannabis crop? It’s true! Fortunately, there are some simple actions you can take to protect your crop.

What is the issue? Spray equipment includes metal componentry which can be susceptible to corrosion by caustic substances. Corrosion of your spray equipment is bad for two reasons. First, it impacts sprayer performance and reduces the life of your investment. Second, corrosion of brass parts can lead to leaching of heavy metals from the brass. Once leached into the spray solution, these metals will be deposited onto the foliage along with your crop protection products. You can see the problem from there: Great risk of a positive heavy metals test on your flower buds!

What preventative actions can be taken? Fortunately, there are some simple product choices and maintenance practices that can be used to virtually eliminate the risk of corrosion. Let’s talk about maintenance first. Water is a universal solvent. Given enough time, it will dissolve most substances. When the impurities are removed from water, it becomes an even better solvent, very nearly caustic. For this reason, never use reverse osmosis water to mix spray solutions! The risk to equipment is simply too great. If you have RO (Reverse Osmosis) water serving your facility, be sure to blend it with a second water source, i.e. tap water, before use in sprayers. Next precautionary measure: Never let spray solution sit in the spray equipment any longer than is necessary. This means you should avoid leaving anything overnight to finish up the next day. This is especially true of the oxidizers that are commonly used for sanitation in cannabis cultivation. The worst-case scenario would be to mix your oxidizer with RO water; please avoid this combination. Also, remember that improper rinsing of spray equipment is the same as leaving solution sitting in your equipment. Be sure to properly clean and rinse all equipment with clear water (not RO!). Draw this clear water all the way through the spray path and out the nozzle to properly flush all componentry.

Back to the oxidizing sanitation products. These are critical for most operations. But, we know that caustic substances are bad news for sprayers. What is a conscientious grower to do? Go with something shiny! Look for equipment that offers an option for stainless steel componentry. The nozzle and other internal fittings should be stainless steel or plastic. Several leading companies offer these options, including both Dramm and Siebring. Learn more about work done by Dramm regarding leaching by downloading this technical bulletin. Griffin offers a full assortment of hydraulic, high volume, low volume and ultra-low volume sprayers. Contact your Griffin salesperson or our Controlled Environment Agriculture team at [email protected] or 800-888-0054 ext 89199 for more details. You can also see and purchase products from Griffin online at More product details are available at and

About the author, Tami Van Gaal: Tami Van Gaal leads the Controlled Environment Agriculture team at Griffin. Her horticulture career spans over 25 years, including an advanced degree from the University of Minnesota and service as part of Griffin’s GGSPro Technical Team. The CEA team serves cannabis growers across the country, bringing proven horticultural techniques and products to increase production efficiencies and protect profit margins.

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