Compressed Air Sprayers
The compressed air (tank-type) sprayer is the most popular, portable and self-contained sprayer. A built-in pump forces air into the sprayer, air pressure is built up in the tank and used to force the spray material through the hose, valve, wand and nozzle. Variable nozzle tips adjust the spray pattern and the wand makes spraying under leaves and into other hard-to-reach places easier. When the user fills the tank, he has pre-mixed the chemicals to a uniform concentration; how much he pumps gives him control of the pressure-high pressure for a fine spray that gives thorough penetration and coverage; low pressure for a coarser spray that reduces drift. The discharge valve controls the on/off function so the user can avoid overspray and wasted chemical.
Handles are provided to carry most tank sprayers, plus some larger units offer shoulder straps. Tanks can be made of blow molded polyethylene, galvanized or stainless steel. They are available in 1/2 to 3-1/2 gallon capacities.
Do not fill the tank more than three-fourth’s full or beyond the “fill to here” spot indicated on the tank. This leaves head room for air to be compressed on top of the spray material when pumped. If little or no air room is left at the top of the tank, you can not build up the pressure needed to spray. Air, a gas, can be compressed to hold pressure, but liquids such as water with chemicals can not.
Poly Pressure Sprayers
The most popular style of compressed air sprayers are ones with blow molded polyethylene tanks. They offer superior strength and corrosion-resistance when compared to galvanized steel, yet are more economical than stainless. In addition, they are lighter weight and easier to handle.
Basic design features to look for include:
- Wide Tank Opening – Easy filling, easy closing, positive sealing cap/cup assembly
- Full Size 10” Pump – Allows for quick pressurizing
- Pressure Relief Valve – Tells you when you have pumped to maximum 45 psi working pressure, avoids over pressurizing and makes releasing pressure safe and easy.
- Comfortable And Easy To Hold Carry Handle
- Heavy Gauge Hose – Long enough to hold the sprayer at your side while in use.
- Positive Action Discharge Valve – Easily disassembles for cleaning.
- In-Line Filters – To prevent nozzle clogging
- Extension Wands – Reaches into and under plants
- Fully adjustable nozzle tip
- Optional Flat Spray Nozzle – For even spraying of large areas
Not all sprayers have every feature. The more they have, the safer and easier the sprayer is to use. Only the premium Gilmour® sprayers have all of these features and are generally considered the best sprayer value on the market today.
Hose-end sprayers are equally popular and ideal for large spraying jobs such as yard wide application of fertilizers, insecticides, selective herbicides and fungicides. There are three types of hose-end sprayers.
Fertilizer Feeders – Dry water soluble lawn or garden fertilizers are placed directly in the spray bottle. The sprayer is connected to the hose and water turned on. Part of the water flow is diverted into the bottle, dissolves and mixes the dry fertilizer. It provides convenience for applying fertilizers but is not accurate enough for applying any other type of garden chemicals. Never apply herbicides or insecticides with a fertilizer feeder.
Pre-Mix Sprayers –Chemical is pre-mixed with water in the sprayer bottle to control the dilution rate. The sprayer is then connected to the water line to spray at a fixed mixing ratio. These units will apply 6 to 20 gallons of finished spray per filling. They are the best choice for spraying wettable powders that need to be mixed with water to spray.
Direct Mix Sprayers – Concentrated liquid chemical is poured into the sprayer bottle where it is mixed directly with water as you spray. Models such as the Gilmour Dial-A-Mix 486 or 362 use a dial to select the mixing rate in teaspoons or tablespoons per gallon. They can spray up to 132 gallons of finished spray per filling. Unused chemical can be returned to its original container for future use.
Spray patterns vary from a wide fan for lawns, gardens and flowers, to a solid stream for distance spraying into tall trees. A gentle spray attachment changes the spray pattern to a gentle, coarse spray to prevent wind drift.
Use this type of sprayer carefully, because overspray and drift are possible.
Designed for larger spraying jobs, backpack sprayers like the 4 gallon Spray Doc BP4, are carried on the user’s back and often have a larger capacity than conventional hand carried tank sprayers. Modern polyethylene models are lightweight, comfortable and easy to use. Intermittent pumping maintains a constant pressure on models with surge tank designs. They produce uniform discharge rates and spray patterns. Capacities range from 31/2 to 5 gallons.
Some sprayers have mechanical agitators to keep wettable powders mixed. How fast you pump determines operating pressure which can reach 90 psi.
Pump Type Dusters range from 1/2 lb. capacity up to 30 lbs. for home or commercial use.
A hand held pump releases air on the “in” stroke of the plunger. The volume of dust discharged and range of carry are controlled by size of pump and speed of stroke.