Pure-Water Window Cleaning: Why TDS, Brush Technique and Rinsing Work Together

Pure-water window cleaning looks like the simplest method in the industry: wet the glass, scrub it with a brush, rinse it with water that has nothing dissolved in it, and walk away. When it fails, it fails because one of the three parts is missing. Water that is not pure enough leaves spots, a brush technique that does not lift the soil leaves a film, and a rinse that does not carry the soil away leaves both on the glass as it dries.

This guide explains how total dissolved solids, brush technique and rinsing work together, and what has to be true of each for a spot-free finish. It is written for cleaning contractors, facility managers and procurement teams evaluating pure-water methods for shopfronts, mid-rise buildings, atriums and glass facades.

Pure Water Window Cleaning Explained: TDS, Brush and Rinse

The method works because water with almost nothing dissolved in it is an effective cleaning agent and leaves no residue when it dries. Ordinary tap water contains minerals, and when that water evaporates it leaves them behind as the spotting and film that glass cleaners are designed to hide. Remove the dissolved solids and the same water dries clear.

The second part is mechanical: a brush agitates the soil so the water can carry it off. Without agitation, the water wets the soil and dries with it still on the glass. The third part is the rinse, which has to be a genuine flow of clean water across the pane rather than a token wetting. Where all three are present, the finish is spot-free without detergent, cloths or a squeegee; where any one is missing, the method produces the complaints that lead sites to conclude that pure water does not work.

That is why the specification is a system rather than a product. The water quality sets the limit, the brush determines whether the soil is lifted, and the rinse determines whether it is removed. Buying a pole and a pump without addressing all three simply moves the failure from the tap to the glass.

Define the Site Condition That Changes the Answer

Four site conditions change what the system has to do. The water at the property sets the treatment: dissolved solids vary between suburbs, between town water and tank water, and between seasons and catchments. The soil on the glass sets the agitation: pollen, traffic film, sea spray, construction dust and kitchen grease all behave differently, and heavier soil needs more brush work before the rinse.

The building sets the access and the volume. Height, obstructions, run-off and the surfaces below the glass determine how the work is done and where the water goes. And the finish standard sets the tolerance: a shopfront judged from the street in raking light is less forgiving than an office partition judged from inside, and the standard decides how much water and time each pane deserves.

Where the site has never used pure water, a test elevation is the practical starting point. Measure the water at the property, clean one section with the intended method, inspect it after it dries, and compare it with the panes the site currently considers acceptable. That test answers the specification questions in an hour.

What Does TDS Actually Tell You?

How much is dissolved in the water, in parts per million.

TDS measures the dissolved mineral content of the water, and it is the number that predicts spotting: the lower the reading at the brush, the less there is to dry on the glass, so single digits are the working target for a spot-free finish.

The measurement has to be taken where it matters. A reading at the tap describes the feed water, not the water reaching the glass, and the difference is the whole treatment train: sediment and carbon filtration, reverse osmosis, deionisation resin, hoses and the pole. Reading at the brush or the outlet confirms what the glass receives, and a reading that drifts upward is the signal that resin is exhausting or a membrane is failing.

Treatment follows the feed. Moderate dissolved solids can be handled by filtration and deionisation alone; high readings usually need reverse osmosis with deionisation as a final polish, and the consumables - resin, membranes, prefilters - are sized against the volume of water the work consumes. Because the feed varies between properties, a crew working across a portfolio either specifies for the worst water it meets or tests and adjusts per building. Freshway Supplies stocks professional window cleaning equipment including poles, brushes and finishing tools, and this overview of what a professional window cleaning kit contains covers how the pieces fit together.

Water Quality, Detergent and Residue

Detergent is usually unnecessary in a pure-water method and works against it. Surfactant left on a pane attracts dust, dries as a film and produces the streaks that the method was adopted to avoid. Where the soil is heavy, the useful response is more agitation, a targeted pre-treatment removed before the rinse, or a second pass - not a change to the water.

Residue also comes from the equipment. Hoses, tanks and brushes that have carried detergent in a previous life contaminate the water they now carry, which is why pure-water systems are normally kept separate from detergent-based equipment. Resin that is exhausted, a membrane that has failed, or a filter that has not been changed all raise the TDS at the brush, and the glass shows it.

A water-quality log is the practical control: the reading at the brush at the start and end of each session, and the date consumables were changed. Where a customer complains about spotting, the log answers the question of whether the water was within specification on that day, which is the same evidence a cleaning contractor needs when the complaint turns out to be about the glazing rather than the clean.

Brush Technique and Rinsing

Technique is where a pure-water system either produces a finish or wastes clean water. The brush has to agitate the whole pane and the frames, working from the top down so soil leaves the glass rather than being pushed across it, and the bristles need enough contact to break the bond between soil and surface without scratching a coating.

The rinse then has to carry that soil away. Practically that means starting at the top and rinsing downward in overlapping passes, keeping the flow continuous rather than intermittent, and paying particular attention to the top edge and the corners, where soil collects and where a weak rinse leaves a line as it dries. On pure-water work the rinse is the step that replaces the squeegee, so it is not a formality: a pane that is scrubbed properly and rinsed badly dries worse than one that was cleaned with a squeegee and a detergent.

The tools support the technique: a brush whose bristles suit the glass, jets positioned to deliver water across the head, enough flow at the top of the pole to rinse properly, and a hose that does not starve the brush when the pole is extended. Where the flow at the top of a pole falls away, operators compensate by scrubbing longer, which is slower and produces a poorer result.

Where a first clean is being done on glass that has never been pure-water cleaned, the work takes longer. Years of detergent film, mineral deposit and traffic soil lift progressively, and the first visit may need two passes. Subsequent visits on the same building are much faster, which is why pure-water programmes are usually priced and scheduled as a cycle rather than as one-off cleans.

Frames, Seals and Adjacent Surfaces

Pure-water work wets frames, seals and sills, and the run-off continues below the glass. On buildings with timber frames, aged sealant, decorative coatings, render or stone, that has to be considered before the method is adopted, and where the surfaces are vulnerable the method may need to be limited to elevations that tolerate it.

The controls are direction, volume and sequence. Rinse downward so soil leaves the building rather than being carried sideways, control the volume so the pane is wet enough to clean and not so wet that water pours into frames and cavities, and clean frames and sills as part of the same pass so the next rain does not carry their soil down the glass.

Below the work, consider what the water lands on: entrances, footpaths, planters, parked vehicles, signage and stock. On retail and hospitality buildings, water landing on a shopfront's doorway during trading is a customer complaint waiting to happen, which is why facade work is usually scheduled around trading hours.

Working at Height and Public-Area Controls

Pure-water pole work removes the fall risk for the operator on reachable glass and introduces a different set: poles in contact with overhead services, poles lifting in wind, water and hose in public areas, and the operator working from roadways or uneven ground. Each needs a control in the method rather than in the operator's judgement.

Height safety in Australia is supported by the fall protection series published by Standards Australia and listed as AS/NZS 1891.1, with regulator guidance setting out the duty for the task, including WorkSafe Victoria's plant guidance and the resources at SafeWork NSW. The framework sits in the Work Health and Safety Regulations 2011.

Weather belongs in the same planning. Wind makes a long pole difficult to control and can lift it against overhead lines, direct sun dries the rinse before it has carried the soil away, and rain makes exterior work pointless. Scheduling around the weather is part of running a pure-water programme rather than an excuse for missing one.

Equipment, Consumables and Maintenance

A pure-water system consumes more than it appears to. Brush bristles flatten, jets block, hose connectors wear, pole clamps lose friction, pumps fail, resin exhausts and membranes degrade. Each has a service life, and the failure that stops a job is usually the cheapest part on the list.

The daily routine is short: check the TDS reading, check the brush and jets, check the hose ends and pole clamps, and confirm the flow at the brush before starting on a building. The periodic routine covers prefilter changes, resin replacement, membrane care and pump servicing according to the manufacturer's guidance, recorded with the equipment rather than remembered.

Stocking follows the portfolio. A crew that cleans several buildings a day needs spare jets, hose connectors and a spare brush in the vehicle, because a blocked jet changes the finish on every pane that follows. Where a system is vehicle-mounted, the tank, pump and fittings deserve the same attention as the pole, since a failure there stops the day.

What to Settle Before Ordering

Confirm the following before a pure-water system is committed to, so the specification reflects the buildings rather than the brochure.

• Water: the TDS at each property, the treatment train required and the volume the work consumes per visit.
• Reach: the highest glass, the obstructions and the working positions, with margin on pole length.
• Output: the flow required at the brush at full extension, and the hose diameter and pump to deliver it.
• Finish: the standard required and the panes the client judges, agreed before the first visit.
• Access and safety: working positions, exclusion zones, weather limits and public-area controls.
• Consumables: resin, prefilters, membranes, brushes, jets and connectors, stocked to the portfolio.
• Records: TDS readings, consumable changes and the method, kept with the equipment.

That list is what turns a method that works on a demonstration pane into a programme that works across a portfolio, season after season.

Questions we get asked most

What TDS should pure water be for window cleaning?

Low enough that nothing visible is left when the water dries, which in practice means single digits in parts per million, measured at the brush or the outlet rather than at the tap. A reading that drifts upward is the signal that resin is exhausting or that a membrane is failing.

Do water-fed poles need detergent?

Usually not on glass. Pure water lifts soil and rinses it away, and the absence of dissolved solids is what stops the water drying as spots. Detergent left on a pane attracts dust and dries as a film, so pure-water equipment is normally kept separate from detergent-based equipment.

How often should a pure-water system be checked?

The dissolved solids reading is checked at the start and end of every session, with the date each consumable was changed recorded against the equipment. Prefilters, resin and membranes are replaced on the manufacturer's intervals or earlier where the reading indicates they are exhausted.

Why does pure-water cleaning leave spots?

Usually because the water was not pure enough when it reached the glass, the rinse did not carry the soil away, or the brush did not lift the soil in the first place. The three work together: check the reading at the brush, check the brush and jets, and rinse top down with a continuous flow.

Conclusion

Pure-water cleaning works when TDS, brush technique and rinsing are all correct. Water that is pure enough leaves nothing behind, agitation lifts the soil, and a proper rinse carries it away; remove any one of the three and the finish spots.

Measure the water at each property, keep the treatment train and its consumables in specification, work top down with a brush that suits the glass, and treat the rinse as the step that replaces the squeegee rather than a formality. Ammonia-based and ammonia-free glass cleaners cover the detergent side of interior work.

Manufacturer technical information: Agar cleaning chemicals and Unger professional window cleaning tools.