When our sprayer pressure does not come up, or takes a while to reach the setting, we blame the pump, when in many cases the problem is in the line leading to the pump.

A sprayer designed and built with some degree of engineering has a filtering system between the tank and the pump, and that system is sized in line with the suction capabilities of the pump. (I have seen sprayers built with no inlet line strainer - I have seen sprayers with undersized inlet lines and strainers)

The pump is the heart of the sprayer and needs to be protected. An undersized strainer and/or inlet line will cause high suction vacuum and put a strain on the inlet side of the pump very much like what Arteriosclerosis and clogged arteries will do to our own hearts. And so will a clogged strainer.

The rule of thumb for inlet lines and strainers is that they be of a diameter equal or greater than the suction end of the pump. Also look at the bulkhead fitting in the bottom of the tank where the suction line attaches and the shut-off valve right after it, these must also be that same size..(there should be a shut-off installed between the tank and strainer so that you can do maintenance work even with a full tank).

Any bottleneck in this system will overtax the pump. If your sprayer has any of the design flaws mentioned above, correct them immediately.

Periodic, and I mean periodic maintenance of inlet strainers is critical to your pump.

Surfactant Problem

When you clean out the mesh in the strainer, look for clumps of spray material. This will tell you that you are not agitating correctly or that your materials are not mixing well with the water - a surfactant problem.

Correct those problems right away and you will have less strainer clogging.

Poor Filtering

Also, look at the screen and make sure it is not deformed as this would cause poor filtering. The holes in the screen should be slightly smaller than the smallest nozzle in your spray system. If your mesh is too tight - very small holes - replace it with a lower mesh number (the lower the number, the larger the holes_ 50 and 20 mesh screens are the most popular, but if you have very small nozzles :D-1 or 8001's - you might need an 80 or 100 mesh filter). Selecting the correct screen will prevent nozzles clogs.

Poor Agitation

Poor agitation will also cause sedimentation of unmixed materials on the bottom of the tank. When the pump starts up these are drawn out all together and overload the strainer. Make sure you flush out the tank and spray lines after use and do not leave any sediment in the bottom or in the strainer.

When you reassemble the strainer, make sure the gasket is properly installed and in good condition. Many times I am called out to troubleshoot a pump and find the strainer is sucking air because the gasket is either not there, broken or crimped.

The pump would much rather pull air than water, because its easier and, when you have air in the system, you don't have pressure or your pressure is erratic.

Odd Objects

Another thing to look for is a clog in your suction line. I have found labels, old rags, socks, poly bags, paper and all sorts of other things clogging the inlet lines usually between the tank and the strainer. One way to check this out is to remove the strainer bowl, open the valve and watch the flow. If it does not come out with force and volume, check for an obstruction.

When initially you have normal pressure and it drops off some 30 seconds to one minute after opening the nozzles, you have an inlet obstruction. Correct it immediately. High suction vacuum may not show itself the same way, but can go undetected until the pump breaks down.

Pump failure will be evident in piston pumps generally in the inlet valve area. The valve discs will break outwards (sucked out). Diaphragm pumps can also have inlet valve failure, but their most common breakage is in the diaphragms. These are literally pulled away from the piston head because of the vacuum. Roller and centrifugal pumps will show cavitation wear in the housings, and seal breakdown.

Look at the pipes, valves and fittings on your spray booms. Make sure you have no bottlenecks on the way to the end of the booms. Remember, if you have a 1/2" pipe boom and the spray must go through a 3/8" valve to reach it, you have a bottleneck.

This can cause lower pressures out at the end of the boom and then your nozzles will not be putting out the same patterns and volumes as those close in.

Be logical and think in terms of an efficient irrigation system: always from larger to smaller until the end. Spend some time on it, look carefully, you may find an elbow, tee, fitting, close coupling, hose nipple, hose, filter, valve, anything that could cause that bottleneck. And it could be anywhere between the pump and the last nozzle.

Spray nozzles clog up because particles in the spray solution that are larger than the orifice get to them, and this causes a waste of time and material that we can easily prevent.

Check the screen on all of your line strainers. Aside from making sure that they are not damaged or bent (which would certainly let large particles get by), check the screen size (mesh) and set them up as follows:

The strainer closest to the nozzles should have a screen size just a little smaller than the orifice of the nozzle. This will assure that particles that could lodge in the orifice and clog it do not reach the nozzle. Spray tip manufacturers recommend the mesh size for each of their tips. Check with your supplier for the proper combination.

If you have another strainer in line between the pump and the nozzles (and this is recommended) that screen size (mesh) can be one or two sizes larger than the last strainer.

And now to the main strainer. The one between the tank and the suction side of the pump.This one can have a screen as big as 16 mesh, which will allow the larger particles in the spray solution to recirculate and thus reduce the suction load on the pump. A fine mesh on this strainer will cause caking-up and blockage and will shorten the life of the pump. (the principal cause of diaphragm failure).

With this set-up, the other strainers down the line will take care of the filtering and, provided that the screens are in good condition, your nozzle blockage should be minimal. This type of filtering under pressure will break down particles in the solution, especially when using wettable powders, and allow them to be sprayed.

Did you ever stop to think as to why the hose going from the sprayer pump to the hand gun is 1⁄2" inch? Most sprayer manufacturers install 1⁄2" inch 600 psi hose as standard for the handgun. Some even put in 5/8" and 3/4" hoses and these can be up to 50 to 100 feet long.

It does not make much sense to have such a large caliber hose carrying all that water when the nozzle at the end of the spray gun is only about 1/16" in diameter. So the hose really should be as small as practical without causing friction losses or bottlenecks.

Generally, the size of hose that works best for hand guns and spray wands is 3/8", 600 or 800 psi, depending on how you spray. This hose is not only cheaper than the 1/2", but also has better working and burst pressure factors. It is flexible and lightweight and, because it is carrying less water, not only is easier to handle while spraying, but gets less wear and tear through abrasion when being dragged along the ground, because of its lower overall weight.

Another bonus is that your can get up to 30% more hose onto on a standard reel, and, if you only have a rack to coil it on, that is also easier and lighter work. So look at your hoses; and the next time you have to replace them, think of going with a smaller size and lightening you or your employee’s load.

One of the most overlooked items in the calibration process and especially in boom sprayers is how the nozzles are aimed.

Generally, we just point them directly downwards or at right angles to the plant (in the case of laterals) and expect the fog they produce to travel in and out of the canopy and cover all the foliage on both sides.

If we make a big enough fog, this will be very true, but constraints on the amount of fog we can make in the future (drift) are going to cut into the efficiency of our coverage, which we took for granted, until now.

Aiming the nozzles so that their pattern penetrates the canopy will greatly improve our coverage and reduce drift. However, we cannot follow a rule-of-thumb on this except to try to get the spray to drive into the plants as low as possible at an angle which will make it "bounce upwards" and travel to most of the areas of the canopy, without producing great amounts of drifting fog.

Each crop has to be looked at with that in mind: how to get the spray down into the canopy before it becomes a fog.

One approach is to use narrow angle nozzles. These would be spaced closer to each other on the boom to make up for the loss of pattern produced by the wider angle nozzles, and the narrow pattern will propel the spray deeper into the canopy, especially if it is aimed forward at an angle of 35 degrees or less to horizontal.

The narrower pattern will travel farther before it begins to "break-up’ and, if you regulate your boom height accordingly, you should notice practically no drift or fogging above the canopy.

Putting more nozzles on the boom because of closer spacing will require you to use smaller orifices to maintain the volume. This you can calculate and calibrate yourself.

In order for this to work, you must use Disc/Core type nozzles. Get away from the Teejet type fan nozzles, they are for herbicides and banding, not for under-leaf coverage. The disc/core nozzles will give you angles as small as 15 degrees. (you have been used to 80 to 90 degree angles until now.)

We are giving you the basic idea and what to look for. It’s up to you to decide how you want to aim your nozzles, but please give it some thought.