Streaking With Water Fed Pole But Not Traditional Decision Tree

Why this matters

A two-story residential customer calls about streaks two days after a water fed pole clean, and the same crew has zero complaints on the ground floor done with squeegees. That mismatch is the single most diagnostic symptom in the trade. Pure-water cleaning only works when the rinse water is at or below 10 ppm TDS at the brush, when the rinse is generous enough to flush every contaminant off the glass, and when the surface is allowed to spot-dry without contact. Streaks on WFP work but not on traditional point to one of three things: water purity slipping during the route, technique on the rinse step, or a glass surface contaminant the pure water alone cannot lift. Working through the branches below in order gets the route back to clean by the end of the same shift.

Symptom presentation

The streaks usually appear after the glass dries, often visible only in side light. Capture the pattern. Vertical streaks running top to bottom indicate inadequate final rinse; horizontal streaks indicate the operator dragged the brush across without fully flushing; spots and dots indicate hard-water carryover, either from poor system performance or from contamination on the brush bristles. Streaks at the top of the lite only suggest the rinse pressure dropped off as the pole extended.

Note whether the streaks are on every window or only on south and west elevations. South and west panes typically have more baked-on contamination (mineral fallout from sprinklers, organic films from pollen) and the same crew technique that cleans the north side may leave residue on the brighter elevations.

Read the TDS at the pole tip with an inline meter or a calibrated handheld at the start, middle, and end of the route. A reading that creeps from 2 ppm at the start to 18 ppm by the third house tells you the resin or RO membrane is exhausted and the route has been running dirty for the second half.

Quick checks at the truck

Test the source water with a TDS pen before the route. A municipal feed in the 150 to 400 ppm range is normal; a feed above 500 ppm reduces resin life dramatically and may indicate a recent utility source change. Compare to the meter reading at the pole tip. Pure water at the pole should be 10 ppm or lower for clear-drying performance; many trade benchmarks target 5 ppm or lower.

Inspect the resin tank pressure differential. A clogged sediment pre-filter starves the resin and shortens its useful life. Replace the pre-filter on the scheduled interval (typically every 30 to 60 route days depending on water quality).

Check the brush. Pure-water cleaning requires the bristles to be clean; bristles fouled with prior building dirt re-deposit contamination on the next house. Rinse the brush at the truck before each property and flush with a clean bucket if the bristles look gray or feel slick.

Isolation tree

Branch 1 - TDS at the pole is above 10 ppm. The resin or RO is exhausted. Swap resin (single-tank deionization systems) or initiate a regen on a dual-tank or rotate to a fresh tank. Pure water cleaning at 10 ppm or higher does not dry clear and will streak on every lite for the rest of the route. After swap, re-rinse every property already done that day to within the streak warranty window.

Branch 2 - TDS is acceptable but rinse technique is short. Watch the operator. The correct WFP rinse is a top-down sweep across the full glass width with the brush off the glass, allowing roughly 30 to 45 seconds of clean water flush per square meter of glazing. A rushed rinse (10 seconds and move on) leaves trace contamination that becomes a streak on drying. Re-train and re-rinse.

Branch 3 - TDS and technique are correct, but specific glass still streaks. Check for a surface contaminant the pure water cannot dissolve. Common culprits are silicone-based protectants previously applied (RainX or generic), oil films from a nearby HVAC condenser, paint overspray, or hard-water stains baked into the glass from prior sprinkler over-spray. These will streak under WFP forever because pure water has no surfactant or solvent to lift the bond. The fix is a traditional clean on the affected lites only, with a glass-rated detergent (Dawn 1:1000 or a commercial glass detergent), followed by a final pure-water rinse to remove the detergent and spot-dry clear.

Branch 4 - the streaks form into a pattern matching the brush bristle layout. The brush is fouled. Pull it, wash with hot water and detergent, and reinstall.

Branch 5 - streaks appear only on the storm side or upper sash of double-hungs. The brush is not contacting the full glass plane because the storm or the sash projection is blocking it. Use a smaller brush or a fan-jet without bristles for those panes.

Confirming diagnosis

Test the truck's pure water output with a calibrated TDS meter (handheld, calibrated against a 342 ppm NaCl reference). The pole-tip reading is the only one that matters for clean-drying performance; the post-resin tank reading can be deceiving if the supply line picks up TDS between the tank and the pole.

For surface contaminant suspects, do a wet-dry test on a small patch. Wet a clean square with deionized water and let it spot-dry. If the test patch dries clear, the WFP system can clean it. If the test patch dries streaky even with hand application of fresh DI water, there is a film on the glass that pure water cannot remove, and traditional cleaning is required.

For brush contamination, hold the brush over a white tray and run clean water through it. If the runoff is gray or carries debris, the brush has been re-depositing for the rest of the day's work.

Remediation

For exhausted resin, regen or swap. For RO membrane fouling, schedule a membrane replacement; membranes typically last 12 to 24 months depending on supply hardness. For brush fouling, replace or wash. For surface contaminants, switch to a traditional clean on the affected lites and document the cause in the file so the next route does not repeat the streak.

Re-route the day's already-cleaned properties before the streaks dry into a long-term film. Pure-water streaks become permanently bonded if left through several wet-dry cycles.

References

• IWCA I-14 Window Cleaning Safety Standard - the trade safety standard, includes references to WFP system operation.
• OSHA 29 CFR 1910.66 Powered Platforms for Building Maintenance - relevant when WFP is used in lieu of platform suspended work.
• ASTM C1036 Standard Specification for Flat Glass - the substrate spec that defines what a "clean" glass surface is.
• Manufacturer technical documentation (Tucker, Unger, Ionic Systems, IPC Eagle) - WFP system operation, TDS targets, resin specifications.
• WCRA (Window Cleaning Resource) field reference - widely-used trade source for WFP best practice and rinse timing.