Streaked glass is almost always a water recovery problem, not a cleaning problem. If the vacuum return cannot lift dirty water fast enough, the squeegee leaves it behind and it dries into a film. Fix recovery first, then look at chemistry.
Operators blame the brush, the detergent and the operator before they blame the return system. In our experience the order is backwards. Most complaint calls start with a clogged line, a full recovery tank or a nozzle that has drifted out of alignment.
How does water recovery work on a glass robot?
Two systems are common. One uses a squeegee blade with a vacuum slot behind the brush; the other uses a vacuum pickup close to the brush line. Both rely on a seal against the glass to create suction. Lose the seal and you lose the recovery, which is why a stiff or lifted seal shows up as streaks.
What causes streaks in practice?
- Recovery tank near full, so suction drops.
- Clogged filter or return line, common with hard water.
- Worn squeegee blade edge.
- Too much detergent, which foams and defeats pickup.
- Cleaning hot glass in full sun, so water evaporates before pickup.
That last one is underrated. Clean early in the morning on south-facing glass and half the streak complaints vanish without touching a single part.
Should you use more water or less?
Use less, delivered better. Flooding the glass to compensate for poor recovery just spreads the problem. Set the flow so the brush is wet but not dripping, and let the return do its job. If you need more water to remove the dirt, the issue is dwell time or chemistry, not volume.
Water quality matters too. Hard water leaves mineral spots even when recovery is perfect, so a simple filtration or deionisation step is worth it on any site with visible spotting. Lingyun Y3 is often specified with a filtered supply for exactly this reason.
Who should not rely on a robot for spot-free glass?
If the site insists on literally spot-free drying in direct sun with no early-morning window, no glass robot guarantees that without a pure-water rinse step. Be honest with the client about the streak risk before the contract, not after. For a documented wash plan, contact the team.
Key Takeaways
- Streaks usually mean recovery failure, not brush failure.
- Check tank level, filter, line and squeegee edge first.
- Too much detergent foams and ruins pickup.
- Clean south-facing glass in the morning, not midday.
- Add water filtration to avoid mineral spotting.