Sprayers Verus Pesticides: How to Limit the Effects of Chemicals on Your Sprayer

The primary wear factor on sprayers and spray equipment is the type of liquids that they spray. Many Pesticides and herbicides have characteristics that make them hard on different materials.

This often results in leaks, weak pumps, or entire sprayer failure over time. With this in mind, it brings up a good question: “How do you safely store these chemicals and avoid the degradation of your sprayers, tanks, and components?”

How Chemicals Effect Sprayers

Chemicals and pesticides affect different materials in different ways. They also behave differently when in cold or warm temperatures, and mixed with other liquids. Here are a few of the main ways that pesticides cause problems for sprayers: 

  • drying out the rubber material used for seals/o-rings
  • solidifying and plugging/gumming up moving parts
  • abrasion on the components
  • Corrosion or rust on metals. 

There are certain products that may break down the materials that a sprayer is constructed with, but this is less common. Here are some examples:

  • Floro-carbons (oils/gas) permeate EPDM rubber
  • DEF attacks and metals.

Leaving Chemicals in Sprayers 

In an ideal scenario, you would drain and rinse your sprayer each time you use it. The negative effects caused by different agrochemicals and pesticides can best be avoided by getting rid of the lingering residue whenever possible

However, anyone who has done some of their own spraying knows that this is not always feasible. What if you have some chemical still left in the tank? What if you are going to spray more tomorrow? This is especially relevant for commercial lawn care and custom applicators who spray daily.

Can You Leave Pesticides in a Sprayer Overnight? 

Yes, in most cases leaving chemicals/Pesticides in your sprayer overnight is not a problem. In fact, from my own experience, you can leave your spray mixture for a few days or even more. However, the longer the chemical is present sprayer, the greater the chance for problems. 

That being said, a sprayer designed for Pesticides, herbicides, etc., will be constructed of materials that are generally compatible with these products, and contact with them will not result in damage to the sprayer, especially considering the chemical solution is mostly water.

Avoiding Chemical/Pesticide Damage to Your Sprayer

The most effective method of avoiding damage from different pest control products is to rinse and flush out your sprayer thoroughly. Triple rinsing and using a tank cleaner are two proven strategies. Both of these methods should be part of your regular maintenance. In addition to prolonging the life of the sprayer, rinsing with a tank neutralizer will prevent cross-contamination when switching between pesticides. Ensuring that pesticides do not get sprayed somewhere they could do damage.

Thoroughly rinsing often goes a long way to prevent the build-up of sludge in your sprayer and sprayer pump, You would be surprised at how easily and quickly residue buildup can occur, especially when using a granular product. This is especially hard on high-flow/high-pressure diaphragm pumps used by commercial lawn and tree care professionals.

Avoiding corrosion and rust can be done by using sprayers and equipment that are made of poly and not metal. Sometimes you might find that a certain pesticide really causes problems. In this case, it may be necessary to consult the chemical company for advice on the type of sprayer to use. 

Convenient Ways to Flush Your Sprayer 

Flushing your sprayer with fresh water is not very convenient. Especially when you have to empty your sprayer and then fill it with fresh water after each time you spray. One way to make flushing out your sprayer more convenient is to have a separate dedicated freshwater tank on your sprayer. 

Adding an extra tank might not be practical for your sprayer, but you can always include an extra valve and connection point for fresh water on the suction side of your sprayer pump. 

Another option is to mix your pesticide/herbicide with the water as it leaves the pump. This keeps chemicals from ever coming in contact with the sprayer pump. Chapin has made a small sprayer for ATVs and lawn sprayers that comes with a smaller separate tank that holds whatever product you want to apply. The larger, main tank holds fresh water only. The pump draws both water and chemical from each tank according to the ratio you select on the mix valve. 

When you are done spraying, you turn the mix valve off and run only fresh water through the system to clean it. You can also easily change the pesticide you are using by swaping out the chemical tank. This is a clever design that can increase the life of your sprayer.

How to Clean Your Sprayer

After using a pesticide or insecticide in a sprayer it is important to clean it. As discussed earlier, triple rinsing is a vital part of sprayer maintenance. It is the technique that is recommended by University extension experts

It is called “triple-rinse” because you fill and rinse the sprayer tank three times. Research and testing have found this to be highly effective in removing up to 99 percent of the remaining chemical residue.

Therefore when cleaning and rinsing the sprayer be sure to rinse it three times. This involves draining the sprayer of all remaining spray solution, and then filling the tank about a quarter full with fresh water. Enough to run fresh water through the entire system for a couple of minutes. Then depending on the type of sprayer, pump the handle and spray out the water, or turn on the pump and run water through the system. Repeat this two more times.

Beyond rinsing the sprayer, you can scrub and clean individual sprayer components.. Depending on the sprayer pump type, it may be a benefit to clean out the pump. The pump is affected by harsh chemical abrasion more than other areas because of all the moving parts. this makes getting left behind residue removed can save you from future problems. 

Here are some pumps that benefit from cleaning: 

12 V Diaphragm Pumps

Example: Shurflo 2088-343-135

As one of the most popular types of pump for lawn and ATV sprayers, you are probably familiar with 12-volt powered diaphragm pumps. Cleaning these pumps is quite simple. After spraying, flush the sprayer out with fresh water. This means running water through the entire system. 

Then remove the inlet/out hoses from the pump. Remove the cover of the pump to expose the check valves and diaphragm plate. These pieces can be rinsed off and gently scrubbed with soapy water. Then after rinsing off a final time, assemble the pump. 

Roller Pumps

Example: Hypro 7560

To clean out a roller pump, first, drain and rinse the pump. Detach the suction hose and discharge hose. You can use compressed air to blow out the pump and make sure any debris is removed. The rollers can be gently washed with soapy water. If you are done using the pump for the season. Plug the inlet and outlet ports and fill the pump with RV anti-freeze. 

Medium & High-Pressure Diaphragm Pumps

Example: Udor Kappa 55

Medium and high-pressure diaphragm pumps require that you change the diaphragms periodically. Typically this is done every few months or 500 hours of use. At that time it is important to inspect the pump cylinders and the pistons for wear and clean out any debris or residue. Flushing the pump out as often as possible is the best way to keep chemical residue from causing problems. 

Storing Pesticides 

Concentrated chemicals and pesticides should be stored in the container that they come in. If you have bulk chemical/pesticides you want to store them in polyethylene tanks. They should be stored in a climate-controlled building if possible, and keep the tanks out of direct sunlight.

If you have mixed chemical solution left in your sprayer tank after you are finished spraying, you can leave the mixture in the tank. However, If you are going to leave the chemical in the sprayer it is still a good idea to disconnect the pump and flush/rinse with fresh water.


The different chemicals used for pesticides can cause damage or wear to the equipment that is used to spray them. That is the case no matter what type of sprayer you use. The good news is you can take some steps to reduce the impact of different chemicals by flushing your pump and following some basic maintenance practices.


I have more than a decade of experience using, building, studying, and testing sprayers in several applications. With the knowledge I have gained I want to provide straight forward and detailed answers for DIY homeowners, farmers, and commercial turf and tree care pros.

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