The Right Backpack Sprayer: Piston vs. Diaphragm

Are you considering purchasing a backpack sprayer?

Today’s sprayers have an abundance of options that can be a bit overwhelming if you do not know what you are looking for. Taking the time to think ahead of the many ways you plan to use your sprayer will help you get the best piece of equipment for your investment.

Backpack Sprayers Have Many Features to Consider...

• Tank Size: Select a tank size that is large enough for your projects, but not so large that you have extra, unnecessary weight. Large tank openings reduce spillage when adding chemicals.
• Tank Materials: Tanks should be made of UV and corrosion-resistant materials for a long life.
• Seals & Gaskets: There are multiple types of seals based on the chemical(s) that you will be using. These parts greatly affect the life and performance of the sprayer, not to mention the prevention of leaks.
• Comfort: Components such as shoulder straps, carrying handles and frame size will affect your comfort and fatigue level when using the sprayer.
• Safety Features: Look for shut-off valves, with lock-on/lock-off feature, to control spray and prevent dripping.
• Nozzles: Interchangeable nozzles allow for multiple spraying tasks.

Another key consideration is the type of pressure pump assembly that will work best for your needs. Backpack sprayers are constructed with either Piston or Diaphragm pumps – each has its benefits:

There are two common types of backpack sprayers; a piston pump and a diaphragm pump. The units look similar until you see the pump housing. The piston pump is typically housed in a tube with a piston that moves up and down to create pressure. The diaphragm is shaped more like a disc and uses a diaphragm to pump in and out to generate pressure.

Prices are usually similar for both types, but there are different reasons why you may want to select one over the other.

PISTON SPRAYERS:

Piston sprayers include a cylinder housing in which, when pumping, a piston moves up and down to create pressure. They are best used for distance as they generate more pressure. The increased pressure also creates finer droplets or a mist that covers well. The distance and finer droplets make them ideal for spraying up into trees or larger bushes and shrubs.

• Most piston models can reach up to 90 psi, which delivers smaller droplet size and has a further reach.
• Use with low abrasive, low viscosity spray liquids such as herbicides and insecticides.
• Easy to repair.
• Not for use with soluble powders, abrasive or bleach solutions. Any powders not dissolved can create sand-like textures in the mix which may score the piston inside the piston-pump sprayers. The advanced wear on the pump caused by the scoring and scrapes can result in reduced pressure or pump failure.

DIAPHRAGM SPRAYERS:

Diaphragm pumps feature a flat, diaphragm inside of a housing held together by screws.  When pumping, the diaphragm flexes up and down to create pressure.  These pumps tend to be more durable because there is no contact with the cylinder wall. Diaphragm pumps produce larger droplets which are better at getting the spray onto your target when spraying weeds, fencelines, and driveways and avoiding drift.

• Diaphragm pumps can reach up to 60 psi.
• Can be used with soluble powders, abrasive or bleach solutions.
• Repairable, however, a bit more time consuming than a piston model.

The simple way to remember uses; if you’re spraying up use a piston pump and if you’re spraying down use a diaphragm. If you may do some of both the diaphragm pump creates the least spray drift and often last longer if cared for well.

• • To properly care for a backpack sprayer, always rinse clean water through them after use.
  • With clean water inside, pump and spray multiple times to clear the pump of spray residue and clean them out.

• Store the sprayer hanging upside down which keeps liquids and dirt from settling in the important components of the pump.

All sprayers are not created equal. The next time you are in the hardware store take a look at both styles of sprayers. Choosing the correct sprayer type from a quality manufacturer will give you the best overall performance and provide service for years to come. Solo and other quality backpack sprayers can last decades if you take care of them. If they end up needing repairs, Solo offers parts to fix nearly any issue.

*Images and information contributed by SOLO.