A used sprayer is one of the few machines on the farm that can turn a good day into a disaster in a single pass. A worn nozzle set or a limping rate controller doesn't just waste chemical — it means skips, streaks, overlap burn, and a herbicide bill you eat twice. Worse, a sprayer that was run hard with the wrong products, or never rinsed properly, can carry residue that injures a sensitive crop weeks after you thought the tank was empty. So the machine in front of you is really two purchases: the iron, and the history of what went through it. Inspect both.
Self-propelled or pull-type: match the machine to your acres
A pull-type (trailer) sprayer is cheaper to buy, cheaper to fix, and rides behind a tractor you already own and know. If you farm a few hundred acres on your own ground and aren't fighting a tight spray window, a good used pull-type is often the smart money. The trade-off is ground clearance, road speed, and the fact that you tie up a tractor and a driver every time you spray.
A self-propelled machine buys you speed, tall-crop clearance, a real cab with rate control at your fingertips, and the acres-per-hour to work a short weather window. It also brings a second engine, a hydrostatic drive, a suspension, and far more electronics to go wrong — and used self-propelled units hide their real condition better because there's more to hide. Buy self-propelled when your acreage or your spray windows genuinely demand it, not because it looks impressive in the yard. Either way, price the machine against what a dealer or independent shop will charge to make it right, not against what it would cost new.
Walk the boom first — it's the most expensive thing to get wrong
The boom is where a sprayer earns or loses its keep, and it's the first thing to inspect because bent and cracked booms are common and costly to fix. Sight down each wing from the tip like you're checking a rifle barrel: it should be straight, and both wings should sit level at the same height. A wing that droops or kicks up has been in the dirt or a fence, and the fold geometry may never true up again.
- Look hard at the weld seams, the fold hinges, and the breakaway joints for cracks, fresh paint, or re-welds; a re-welded boom section usually means a past wreck and a future failure point.
- Fold and unfold the boom through its full range if you can — it should move without binding, slamming, or drifting down on its own, which points to worn cylinders or tired accumulators.
- Confirm the boom stays even in height across its width when leveled; a section that hangs low will double-dose that strip and starve the next pass over.
- Walk every nozzle body: caps should be tight, check valves and diaphragms shouldn't drip, and the tips should all match, because a mixed bag of brands, colors, or wear states means uneven output and a full nozzle replacement in your near future.
- Pull a few tips and eyeball the orifice; worn tips open up, spray a coarser pattern, and quietly over-apply, so plan on flow-testing the boom against the tips' rated output before you trust the rate.
Pump, plumbing, and tank: hunt for chemical damage
Farm chemicals are hard on rubber, plastic, and seals, so the wet system tells you how the machine was cared for. Start at the tank: look inside with a light for heavy chemical crust, staining, or a scale ring that never got rinsed, and check the outside and the sump for cracks, crazing (a spiderweb of fine cracks in the plastic), and weepy fittings. A tank left full of product over a winter or two gets brittle.
Follow the plumbing. Hoses should be supple, not sun-checked and stiff; clamps shouldn't be rusted or leaking; and the manifolds and valve bodies shouldn't be caked. Ask them to run clean water through the system so you can watch it prime, build pressure, and hold it. A centrifugal pump that won't build rated pressure, or a diaphragm or piston pump that pulses or leaks, is a real bill — and on some machines the pump is buried and labor-heavy to reach.
- Open the main filter and the nozzle screens: a clean, intact screen set says someone maintained it, while crushed or missing screens and a filter full of gunk say they didn't.
- Watch for drips at every joint under pressure, because a sprayer that seeps standing still will leak worse in the field and coat the frame in corrosive product.
- Confirm the agitation system actually stirs the tank; poor agitation lets product settle out so your rate wanders across the load.
Rate controller, GPS, and section control: the electronics you can't eyeball
Modern sprayers live and die by the rate controller and the section-control electronics, and these are exactly the parts you can't judge by kicking a tire. A dead flow meter, a flaky boom-section module, or an outdated controller your monitor won't talk to can cost more than an engine repair, and parts for discontinued systems can be impossible to find.
Power it up and make it work in front of you. Watch the controller read a flow rate and a pressure while water runs, toggle each boom section on and off and confirm the right section actually shuts, and if it has automatic section control (swath shutoff) and GPS, verify the receiver acquires and the machine knows where it is. Confirm which controller and display it runs, whether that brand is still supported, and whether it will integrate with the guidance and monitors you already own. If the seller says a feature works but won't demonstrate it, treat that feature as broken until proven otherwise.
Tires, clearance, and track: fit it to your crop and your ground
Sprayer tires are both a safety item and a crop-fit item, and they're narrow, tall, and expensive to replace. Check that the row spacing and tire width actually fit your crop and your rows; a machine set up for someone else's spacing can cost you a full tire-and-wheel change or leave you crushing plants every pass.
Look at clearance against the tallest crop you'll spray over — not enough clearance means you're done spraying earlier in the season than you need to be. Inspect the tires for weather cracking in the sidewalls, uneven wear, and mismatched sizes, and if it's self-propelled, confirm the adjustable track (if equipped) actually moves and locks where you set it.
Hours, engine, and hydrostat on self-propelled machines
On a self-propelled sprayer, hours matter but pattern matters more: a machine that sprayed steady acres for a custom applicator can be healthier at high hours than a neglected low-hour unit that sat and corroded. Read the hours against the wear on the pedals, steps, and seat, and treat a big mismatch as a flag worth asking about.
Go through the engine and drive like you would on any machine. Cold-start it yourself and listen, watch for smoke that doesn't clear, and pull the engine oil and the hydraulic/hydrostatic dipsticks to check for milky oil or a burnt smell. The hydrostatic drive is the heart of the machine — drive it, and feel for one that pulls evenly, holds on a hill, and doesn't shudder, whine, or lose power as it warms up. Ask for service records and confirm the engine, hydro, and boom hydraulics have actually been serviced on schedule.
- Check the ground where it was parked for coolant and hydraulic leaks, and look around the hydro pumps and wheel motors specifically.
- Test the brakes, the park function on a slope, and the steering through full lock both ways.
- Confirm the suspension (if equipped) rides level and isn't sagging on one corner.
Residue and contamination history: ask what went through the tank
This is the check most buyers skip, and it's the one that can wreck a crop. A sprayer is only as clean as its last operator's rinse habits, and some chemistries — certain hormone-type herbicides and long-residual products — cling to hoses, tank walls, and pump internals and can injure a sensitive crop long after the tank looks empty. If this machine sprayed pastures, roadsides, or a very different rotation than yours, that history is a real risk you're buying along with the iron.
Ask directly what products ran through it, whether it was ever dedicated to hard-to-clean chemistries, and how it was cleaned and stored. Then plan a full clean-out of the entire system — tank, booms, and every nozzle — with a labeled tank cleaner before you trust it on your own ground, and read the labels of the products you'll be spraying for their specific cleanout steps. Where you can, buy from a seller who'll give you the machine's history straight, and it's worth weighing a dealer's reputation through reviews — especially verified, proof-of-purchase reviews and ones written months later about how service and warranty claims were actually handled.
The short version
- Decide self-propelled versus pull-type by your real acreage and spray windows, not by what looks impressive in the yard.
- Inspect the boom first: sight down both wings for straightness, hunt for cracks and re-welds at the folds, and confirm every nozzle tip matches and doesn't drip.
- Run clean water through the system to watch the pump build and hold pressure, and check the tank and plumbing for chemical crust, crazing, and brittle hoses.
- Make them power up the rate controller, section control, and GPS and demonstrate each feature, because undemonstrated electronics are broken until proven otherwise.
- On self-propelled units, read hours against wear, drive the hydrostat until it's warm, and check the engine and hydraulic oil for milky or burnt signs.
- Ask what chemicals ran through the tank, then clean out the whole system with a tank cleaner and follow your product labels' cleanout steps before spraying anything sensitive.