Calibrating Termite Application Equipment

Editors note: A new publication from Purdue University Extension, lead-authored by Purdue Pesticides Program Director Fred Whitford and titled Calibrating for a Liquid Termiticide Application, is now available. The guide describes the process for calibrating termite application equipment so applicators apply the correct concentrations and volumes to structures based on product label instructions. Download for free or order at https://ppp.purdue.edu/resources/ppp-publications (search PPP-144). The following excerpt includes a visual guide to calibration.

You can determine total gallons of solution needed by graphing. Most termiticide products require applicators to know the outer linear measurement and the depth of footer to determine how much termiticide will be needed to treat the structure. The graph should indicate on each section of exterior wall the length of the wall and the depth of footer (see illustration, below).

For instance, a wall is 20 feet long and the footer is 3 feet deep. If the application rate calls for 4 gallons per 10 linear feet x depth of footer, this area will require an application of 24 gallons of solution. By adding up the gallons used for each section, applicators can calculate the total amount of product they need for the entire structure.

KNOW THE EQUIPMENT’S GALLONS PER MINUTE. The normal target flow for most termite application rigs is 2 gallons per minute. To check your flow rate, all you need is a bucket with graduated gallon measurements and a stopwatch. To determine flow, dispense the liquid from your injector rod or gun in the graduated bucket for one minute — you also can collect the liquid for 30 seconds and multiply the amount by 2. Alternatively, you can use a stopwatch to see how long your termiticide rig takes to apply 1 gallon.

Note the pump’s pressure at the start of collecting. If the rate is more or less than 2 gallons per minute, adjust the pump pressure. The lower the pressure, the less flow and vice versa — so, increasing the pressure increases the product flow. Continue adjusting the pressure until the attachments are each putting out 2 gallons per minute.

Record the operational pressures separately for each of the application tools to ensure that the equipment is putting out 2 gallons per minute. Refer to the specific pressures for each tool when you use them, then set the correct pressure before starting the treatment. Inline flow meters are also available for some termite rigs, but they may require calibration. You also should routinely calibrate these meters using this simple method to verify their accuracy.