How to Test a Used Pool Robot Before Buying

Why Test a Used Pool Robot?

Robotic pool cleaners represent a significant investment, with quality models costing $800-2,000 new. The used market offers excellent opportunities to find premium brands like Dolphin, Polaris, and Hayward at substantial discounts. However, these sophisticated machines combine multiple motors, pumps, brushes, and electronics that all must work together for effective pool cleaning.

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Pool robots face harsh operating conditions: chlorinated water, UV exposure, debris impacts, and constant submersion. Unlike land-based robots, failures often aren't visible until the unit is in the water. Motors can develop seal leaks, brushes wear down, and cables degrade from chemical exposure. A non-functional pool robot is expensive to repair and often not worth fixing.

This comprehensive guide teaches you to evaluate every critical component of a used pool robot. From testing drive motors to inspecting cable integrity, these checks will help you find a unit that will reliably clean your pool for years. The ideal test involves running the robot in the seller's pool, but even dry testing can reveal most issues.

Drive Motor Evaluation

Pool robots typically have two or more drive motors that power the tracks or wheels. These motors must produce enough torque to climb walls and navigate pool obstacles while submerged.

Dry Motor Test

With the robot out of the water, power it on and observe the drive system. Both sides should move with equal speed and power. Lift the robot and watch the tracks or wheels spin freely. Any hesitation, uneven movement, or grinding sounds indicate motor or gearbox problems.

Motor Sound Assessment

Listen carefully to the motors during operation. Healthy motors produce a consistent hum. Grinding, clicking, or rattling indicates worn bearings, damaged gears, or debris contamination. Water intrusion in motors often causes corrosion that leads to grinding sounds.

Resistance Test

While the robot is running (out of water), try to gently slow down each track or wheel with your hand. Both sides should resist equally. If one side stops easily while the other fights back, there's likely a motor or transmission problem on the weak side.

Pump & Suction System

The pump motor creates suction that pulls debris into the filter. This is typically the most powerful motor in the robot and is critical for cleaning effectiveness.

Pump Activation

When powered on, you should hear the pump motor engage. It produces a distinctive higher-pitched whine compared to drive motors. The pump should run continuously during cleaning cycles. Any pulsing, stopping, or fluctuating sounds indicate pump problems.

Impeller Inspection

If accessible, check the impeller for damage or debris. Located in the pump intake, the impeller should spin freely when moved by hand. Chipped or cracked impeller blades reduce suction significantly. Hair and debris wrapped around the impeller shaft can burn out the motor.

Seal Condition

Pump motors have seals that keep water from reaching the motor windings. Look for any white salt deposits or corrosion around the pump housing, which indicate past or current seal leakage. Water intrusion is fatal to motors and often not economically repairable.

Suction Verification (In-Water)

When testing in water, place your hand near the intake. You should feel strong, consistent suction pulling water and debris into the filter. Weak suction indicates pump wear, impeller damage, or air leaks in the system. Good suction is essential for effective cleaning.

Brushes & Tracks Assessment

Brushes scrub pool surfaces while tracks provide mobility. These are wear items that need periodic replacement, but their condition indicates overall maintenance and remaining useful life.

Brush Condition Check

Examine all brushes carefully. Bristle brushes should have full, even bristle length. Worn brushes appear flat or unevenly worn. Foam brushes should be supple, not hard or cracked. Missing brush sections leave uncleaned areas. Check that brushes spin freely and are properly secured.

Brush Motor Function

Most robots have separate motors for brushes. Power on the unit and verify all brushes rotate. The speed should be consistent without stuttering. Some robots reverse brush direction periodically - this is normal. Non-rotating brushes indicate motor failure or drive belt issues.

Track/Wheel Inspection

Examine tracks for cracks, missing pieces, or excessive stretch. Tracks should fit snugly on the drive wheels without excessive slack. Check wheel hubs for cracks and ensure wheels spin freely on their axles. Worn tracks cause traction problems, especially on pool walls.

Climbing Capability

Wall climbing depends on proper track tension and brush scrubbing action creating suction. Test this in the pool by watching if the robot successfully climbs and cleans walls. Robots that can only clean the floor due to worn tracks or brushes are significantly less valuable.

Filtration System

The filtration system captures debris from the pool. Filter type affects what the robot can clean and maintenance requirements. Inspect all filtration components carefully.

Filter Basket/Canister

Remove the filter basket or canister and inspect it. The housing should be intact with no cracks. Basket designs make emptying easy but may miss fine particles. Cartridge designs capture smaller debris. Check that the basket locks securely in position.

Filter Media Condition

Examine the filter material itself. Mesh screens should be intact without holes or stretched areas. Foam filters should be supple, not deteriorated or compressed. Fine micron filters should be clean enough to see through when held to light. Heavily stained or damaged filters need replacement.

Filter Options

Many robots offer multiple filter options: standard mesh for leaves and debris, fine filters for algae and sand, and ultra-fine for removing smallest particles. Ask which filters are included. Having multiple filter types adds value and versatility.

Access Door Seals

The filter access door must seal properly to prevent debris escape. Check door seals for wear, hardening, or damage. Test that the door closes securely and latches properly. Failed seals allow cleaned debris to escape back into the pool.

Cable & Swivel System

The power cable connects the robot to the power supply and is one of the most common failure points. Cable damage from UV exposure, chemical degradation, or improper storage is common in used units.

Cable Inspection

Examine the entire length of the cable carefully. Look for cuts, cracks, kinks, or exposed wires. The outer jacket should be supple, not brittle or cracked. Pay special attention to connection points at both ends, where damage often occurs. Chemical exposure often causes yellowing or stiffness.

Swivel Function

Most quality robots include a cable swivel that prevents tangling. The swivel should rotate freely in both directions. A stuck swivel causes cable tangling, which can damage the cable and cause the robot to get stuck. Test swivel rotation with light resistance.

Cable Length Verification

Confirm the cable is long enough for your pool. Standard cables are 50-60 feet; larger pools may need extensions or longer cables. Some sellers may have shortened damaged cables. Measure the cable or compare to the model's specifications.

Connection Points

Check how the cable connects to both the robot and power supply. These connections should be secure with no corrosion. Water-tight seals are critical. Damaged or corroded connections can cause intermittent power or complete failure. Some robots have floating cables that reduce tangling.

Power Supply Testing

The power supply converts household AC power to the low voltage the robot uses. It also contains the control electronics for programming and scheduling. Power supply failure is common and can be expensive to replace.

Power Supply Condition

Examine the power supply housing for cracks, water damage, or UV deterioration. The unit should be designed for outdoor use but shows wear from sun exposure. Check that the cover closes properly and all indicators are visible. Power supplies should be stored out of direct sunlight.

Indicator Light Test

Power on the system and verify all indicator lights work. Most power supplies show power status, operating mode, and error codes. Consult the manual or look up indicator meanings for that model. Flashing error codes indicate problems that need diagnosis.

Timer and Programming

Test all programming functions if equipped. Set a cleaning cycle and verify the display responds correctly. Weekly scheduling allows automatic pool cleaning. If programming matters to you, ensure all functions work properly. Basic units may lack advanced programming.

Remote Control (If Equipped)

Premium robots include remote controls for directing cleaning or retrieving the robot. Test all remote functions: directional control, spot cleaning, retrieval. Some remotes are waterproof for use near the pool. Missing or non-functional remotes reduce convenience but not cleaning ability.

In-Pool Testing Protocol

The ultimate test is watching the robot clean in an actual pool. This reveals issues that aren't apparent in dry testing and confirms the robot is truly pool-ready.

Initial Submersion

Slowly lower the robot into the pool while holding the cable. It should sink and settle on the bottom. Air bubbles escaping are normal - the robot needs to expel air from the filter chamber. If the robot won't sink, there may be trapped air or flotation problems.

Floor Cleaning Performance

Watch the robot clean the pool floor for 5-10 minutes. It should move in a pattern that covers the entire floor without getting stuck. The unit should maintain suction to the floor and not lift or drift. Visible debris should be picked up as the robot passes.

Wall Climbing Test

Observe wall climbing if applicable. The robot should transition smoothly from floor to wall and climb to the waterline. It should clean while climbing, not just driving up the wall. Falling off walls repeatedly indicates worn tracks, brushes, or pump issues. Some robots don't climb walls - verify capabilities.

Waterline and Corner Cleaning

Watch how the robot handles the waterline (where grime accumulates) and corners. These are challenging areas that reveal overall cleaning effectiveness. Premium robots have features specifically for waterline scrubbing. Corners should be reached and cleaned, not skipped.

Cable Management

Observe the cable during operation. It should pay out and retract without tangling. The swivel should keep the cable from twisting. If the cable tangles and restricts movement, the robot's cleaning pattern will be affected. Severe tangling can cause the robot to get stuck.

Pool Robot Brand Guide

Brand significantly affects reliability, parts availability, and cleaning performance. Here's what to expect from major pool robot manufacturers.

Used Pool Robot Pricing Guide

Pool robot values depend on brand, model, condition, and included accessories. Premium brands retain value better than budget options.

Final Testing Checklist

Complete this checklist during your evaluation. Check off items as you verify them. Unchecked items indicate potential issues.