Why a Pool Robot Misses Spots
The same corner staying dirty usually points to one of a few causes. Sometimes it's the route. Sometimes it's the robot's size, the mode, or something in the pool.
Reasons a spot gets skipped
By Maytronics' account, corners, crevices and the join between floor and walls all belong to the floor job of every robot.1 So a corner left dirty is worth noting. It is also worth checking against your manual, since models differ.
Wikipedia says the brushes help remove particles from the floor and walls.2
Other causes sit in the settings. Maytronics says wall-climbing capability varies by model, and that floor-only models leave walls and the waterline needing manual scrubbing.1 Check your manual for what your model cleans.
Cause and check
| What you see | What to check |
|---|---|
| One corner is always dirty | Your manual's notes for your model |
| Walls or waterline stay dirty | Whether your model cleans walls, or is floor-only |
| Whole pool is patchy | Cycle length and mode, per the manual |
Cycle lengths vary by mode. Some makers offer short cycles aimed at one area.1 A short mode may skip the rest on purpose.
Switching modes without noticing is an easy mistake. Check what the display or app shows before you start. [fig:miss-check]
Filter and brushes
Maytronics says a clogged filter reduces suction and cleaning effectiveness. It also says worn brushes reduce scrubbing effectiveness on walls and the waterline.1 So a dirty spot is not always a route problem. It can be a sign that a part needs attention, and that is worth raising with the maker if the manual does not explain it.
How to check and clean those parts is set out in the maker's manual for your model. Follow it rather than guessing.
Random paths leave gaps by chance
A patent on pool cleaner control says older cleaners generally operate in a random pattern. Criss-crossing for long enough, along varied paths, is what is meant to cover all or nearly all of the floor.3 "Nearly all" leaves room for the odd patch.
The same patent says a regular pattern can be knocked off course when the cleaner gets blocked by a corner or other obstacle.3
Timers and waterline
Wikipedia says some machines use delayed timers to stay at the waterline for a moment, where more dirt gathers.2 Time spent there is time not spent elsewhere.
What to do about it
Keep notes over a few cycles. Jot down the date, the mode and which spots were dirty afterwards. Patterns show up fast on paper. One odd result proves little. Cleaning and maintenance steps come from the maker's manual. For how steps and benches behave, read Steps, Ledges and Benches: How Robots Handle Them.
Notes and sources
- What Is a Robotic Pool Cleaner?, Maytronics
- Automated pool cleaner, Wikipedia
- Pool cleaner directional control method and apparatus, Google Patents (US6299699)
Keep reading
How Pool Robots Find Their WayA robotic pool cleaner starts with no map. Here's how it turns at walls, covers the floor and decides where to go next.
Random and Planned Cleaning Patterns ComparedWhy a pool robot zigzags in one pool and runs neat lines in another, and what each pattern suits.
Gyroscopes and Sensors in Pool Robots ExplainedWhat a gyroscope, an accelerometer and bump sensors do inside a pool robot, in plain words, and what each one can't do.