Most skylight robot failures trace to three wearable parts: the suction skirt, the brush, and the water filtration system. Checking them weekly and replacing on schedule costs far less than a stalled cleaning cycle.
Maintenance is unglamorous and therefore skipped. A robot that cleans a 1,000 m2 roof every month runs hard for its hours, and wear is real. The good news is that the failures are predictable, which means they are preventable.
How often should you replace suction cups or skirts?
Inspect weekly, replace every 6 to 12 months on heavy use. The skirt is what keeps suction contained. Once it stiffens, cracks or takes a set, air leaks and grip drops. On a robot working dusty industrial roofs, expect the shorter end of that range.
A simple test. Park the robot, run the pump, and listen. A leaky skirt hisses. If suction falls off faster than it used to, the skirt is the first suspect, not the motor.
What wears out on the brushes?
Bristle length is the wear indicator. When the brush has lost roughly a third of its original length, it stops agitating dirt and starts polishing over it. That is when streaks appear on glass and the operator blames the chemistry.
Brush life depends on surfaces. Smooth glass is gentle. Textured or anti-slip coated glass eats bristles. Hard water scale also dulls the cleaning edge, and a scale-heavy site may need brushes replaced twice as often.
How do you keep the water system working?
Filtration is the quiet killer. Hard water leaves mineral film, and the filter that should catch it clogs. When it clogs, pressure drops, the spray pattern weakens, and the robot lays down spotted water instead of sheeting it off.
| Part | Check | Replace |
|---|---|---|
| Suction skirt | Weekly | 6-12 months |
| Brush | Weekly | 3-9 months |
| Water filter | Every tank | 1-3 months on hard water |
| Battery | Monthly | 2-3 years |
What about the battery and motors?
Lithium packs degrade with heat and with being stored full. Store at around 50 percent charge if the robot sits idle for weeks. Cold sites accelerate capacity loss, so a winter-stored machine often comes back with less runtime than it left with.
Motors and pumps are usually annual-service items. If the machine has a service interval from the maker, follow it. A pump that fails mid-cycle on a steep roof is not just an inconvenience, it can leave the robot stranded until someone goes up.
Where do owners waste money?
Replacing the whole robot when one skirt would fix it, or conversely running a brush to death and scratching coated glass that then needs professional polishing. Both are costly. A ten-minute weekly check plus a stocked spares box solves most of this. Keep at least one spare of every wear item on site.
Which standards matter beyond CE?
For the electrical side, look for evidence against the low voltage and EMC directives in the technical file. For battery safety, transport rules are separate from product rules, and shipping a lithium pack without the right paperwork is a customs problem waiting to happen. For lifting, the machine’s own handling points should be rated and marked.
What records should an operator keep?
A simple log covering each clean, the machine used, any fault, and the parts replaced. It sounds like admin, but it is exactly what an insurer or auditor asks for after an incident, and it tells you when a skirt is due before it fails on the roof.
Where compliant machines still catch people out
- A CE mark on the charger mistaken for CE on the robot
- IP claims with no test evidence behind them
- No local-language manual for operators
- Spare parts unavailable, making a compliant unit unusable
What does a first deployment look like in practice?
Day one is mostly documentation and handling. Confirm the CE file names your model, check the IP evidence, and record the battery transport paperwork. Then walk the access route and agree where the machine will be staged and charged. Only after that does the robot go on the glass.
The first cleaning cycle should be treated as a trial. Measure the real throughput, note where the water runs short, and watch how the skirt behaves on wet panels. What you learn in that first cycle sets the schedule for every clean after it.
How do you brief a new operator?
Keep it short and physical. Show them the suction reading on a good panel, then on a worn skirt, so they can feel the difference. Show them where the water filter sits and how to swap it. Then let them run one full pass under supervision before working alone.
The commonest avoidable failure is an operator who does not know what normal suction sounds like, and so misses a leak until the robot stops climbing mid-roof.
Does weather stop a clean?
Wind is the main stopper. High gusts make placement unsafe and can push a light machine sideways even with good suction. Rain during a clean is usually tolerated on flat glass, but heavy rain defeats the purpose because it re-dirties the glass as the robot passes. Check the forecast and work the dry windows.
Cold is the quieter problem. Near freezing, water on the skirt can stiffen the rubber and weaken the seal. On winter sites, clean in the warmest part of the day and inspect the skirt more often.
Key Takeaways
- Suction skirts, brushes and filters cause the majority of robot failures.
- Replace suction skirts every 6-12 months; brushes every 3-9 months.
- Change the water filter monthly on hard-water sites, or spotting follows.
- Store lithium batteries at about 50 percent charge for long idle periods.
- Keep a spare of each wear item on site to avoid multi-week downtime.
Need filters, brushes and skirt kits for your machine? Check availability.