My main expertise is in water movement and wastewater treatment in the field; I especially love applied science that works for the professional in the field. I invented the Aardvark Borehole Permeameter and Soilmoisture heard about my invention and contacted me. I was truly impressed with their flexible technical staff who, after much work on their part, turned my design into the world's only automated Borehole Permeameter: tough, portable, reliable, highly accurate, and complete with software. Still known as the Aardvark, it is now sold worldwide through their extensive global network. I am proud to have my name and invention associated with Soilmoisture Equipment!

Thomas Macfie,
Inventor of the Aardvark Permeameter

Home :: Technical Tips on the 2900F Quick Draw Probe

Technical Tips on the 2900F Quick Draw Probe

The 2900F is a tool that is used in a dirty and corrosive environment (fertilizer amended soil). As will all tools, they will last longer if they are maintained regularly. The 2900F is an excellent tool that will give the user many years of service if properly maintained.

Most of the calls we receive on the Quick Draw relate to questions regarding slow response time or the unit does not work at all. These problems can easily be avoided through proper maintenance. Here are some common questions we receive and our answers.

"The unit worked fine last year, but doesn't work now. What is the problem?"
If the sponge has dried out then there is probably corrosive solution inside the brass capillary tube inside the Quick Draw. The corrosion can totally plug up the capillary tube or severely reduce water flow. To cure this problem remove the ceramic tip and O-rings (page 11 of your operating instructions). Using a 2-foot length of 0.025 diameter piano wire, insert the rigid wire inside the capillary tube and run it up and down repeatedly to remove any corrosive buildup. Most of the corrosion will be near the ceramic tip. Flush out the Quick Draw with clean water by removing the Null Knob, filling the reservoir (in the handle) with clean water (see page 3 of your operating instructions) then blowing pressure into the reservoir to force water down and out the capillary tube (a good set of lungs works well for this purpose). If you collect the water that comes out of the 2900F, then you should see little pieces of lime deposit and other solid salt accumulation. Reassemble the unit with new O-rings and ceramic tip and service the unit as you normally would, according to your operating instructions.

"The response time has slowed down considerably. What can I do?"
The ceramic tip may have dried out (is the sponge wet?) And salts may have deposited on the surface of the ceramic . To cure this problem, sand the ceramic tip very lightly with a 320 grade wet-or-dry Carborundum sandpaper. Now check your response time. If the response time starts improving, repeat the sanding procedure until the tensiometer response time is under 5 seconds from 50 cb to 10 cb in water (page 5, step 11, of your operating instructions).
General Maintenance
After every use, using a small bottle of water, wash the excess soil off the body and ceramic tip. This will prevent corrosive mud from accumulating in the sponge inside the carrying case. This will also prevent clogging of the ceramic tip that will degrade response time (particularly useful in very fine textured clays).

When you store your unit for the day, fill a wash bottle with a very dilute solution of chlorine bleach (such as Clorox). Shelfgrade Clorox is about 30% sodium hypochlorite; dilute this to about a 3% solution in water. Insert the Quick Draw tip into the wash bottle containing the diluted Clorox, making sure the ceramic tip is completely below the water level. Turn the Null Knob counterclockwise to draw the solution into the capillary tube. Open the Null Knob 2 or 3 turns, but DO NOT turn past the red ring on the Null Knob (page 4 of your operating instructions). By drawing this solution into the Quick Draw you will dilute any dissolved salts that may be present. To flush the solution out, turn the Null Knob clockwise to pressurize the tensiometer. Water should drip out of the ceramic tip. Continue to turn the Null Knob clockwise until it has returned to the fully closed position. Repeat this process at least three times at the end of each use. This will keep your Quick Draw fully operational.

Winter Storage
Before storing your Quick Draw for the winter, clean your tensiometer thoroughly, flush with dilute Clorox and be sure that the sponge inside the Carrying Case is fully wetted. This will keep the tip from drying out and prevent salts from accumulating on the outside of the ceramic tip.

Do not store the 2900F in an area that will freeze. The Quick Draw is a water-filled device and can freeze. If it does freeze, the vacuum dial gauge may rupture requiring the purchase of a new gauge.