Can windows be cleaned with a garden hose?

Start with the list itself. The PGT, CGI and WinDoor care and maintenance instructions say: “Do not use the items below on your windows, screens, doors, or hardware. These improper tools may void your warranty and/or damage your products.” The first item under that heading reads “A power washer or garden hose.”

The guide does not mention it once and move on. Its glass steps open: “Begin by rinsing your glass with clean water to remove dirt and dust particles that can cause scratches during the cleaning process. As mentioned above, avoid using a power washer or garden hose.” The final step says it again: “As stated above, avoid using a power washer or garden hose.”

So why would a window maker name a hose at all, on the same line as a machine built for force? The lines quoted here give a consequence, a possible void warranty or damage, and they give no mechanism, so this page does not invent one. What the guide makes plain is that it treats the two as a single item, not as a strong tool and a gentle one. The power washer half of that line is its own term, pressure washing.

Two limits apply. This is those makers' instruction for their own products, and another brand's rule is printed in that brand's own care guide. The warranty consequence is their sentence about their products, and it is not a rule for every window.

Ruling out the hose is not ruling out water. The guide's own procedure opens with a clean-water rinse to lift the dust that can scratch, and it ends by telling owners to “Rinse your glass thoroughly with clean water to prevent the cleaning solution from leaving a film on your glass.”

Between those rinses it names the tools it has in mind: a soft, water-saturated cloth or a pre-mixed glass cleaner, with any run-down rinsed and dried quickly so the cleaner leaves no residue. It asks for light pressure, because excessive scrubbing can lead to scratches, and for each window or door to be cleaned and rinsed individually. The picture is a careful routine, one window at a time, with clean water at both ends.

The trade's routine method, as NGA publishes it, runs differently: NGA has the glass soaked with clean water and a mild, non-abrasive solution, then a squeegee removes all of it. That sequence is set out as the soak-and-squeegee method on the window cleaning page.

The second test has nothing to do with pressure. The U.S. Geological Survey writes that whether water comes from a kitchen faucet, a pool, the ground or the sky, “the water will contain significant amounts of dissolved substances, minerals, and chemicals,” and that the most common dissolved substances are salts.

The water evaporates and what was dissolved in it does not, so that material stays on the glass. USGS gives a household example: the spots or film on glasses taken out of a dishwasher are hard-water residue, and it defines hardness as the amount of dissolved calcium and magnesium in water. On a window the same leftovers show as spotting, and water carrying a lot of calcium and magnesium is what the term hard water describes.

NGA draws the glass consequence in its description of the pure water technique. Because that rinse is generally allowed to evaporate, the water must carry 20 parts per million of total dissolved solids or less to prevent spotting and streaking, and “The use of tap water is not acceptable.” Why treated water dries without those marks is argued in why pure water dries without leaving spots.

One number that sometimes gets pulled into this is EPA's. Its secondary drinking water standard for total dissolved solids is 500 mg/L, listed for noticeable effects such as hardness, deposits and staining. It is a guideline for drinking water, not a figure for glass. No hardness or dissolved-solids reading for any Naples utility's water is printed here; that figure is the utility's to give.

The water in NGA's pure water technique is made, not drawn. NGA calls for treatment by ion exchange and/or reverse osmosis equipment, and EPA, writing about drinking water, counts reverse osmosis among the treatments that remove total dissolved solids.

That is the real line between a rinse that is left to dry and a hose rinse. It is not only how the water arrives. It is what is still in the water when it lands. A garden hose delivers whatever the supply carries, and NGA's specification exists because that dissolved load is what spots the glass as it dries.

Rain is not treated water either. USGS includes water that falls from the sky among the waters that carry dissolved substances, which is part of the question in whether windows can be cleaned in the rain.

If a hose is what is at hand, the documents above reduce the decision to three questions.

• Who made the window. For a PGT, CGI or WinDoor product, the makers' guide has already answered: no garden hose. For another brand, the answer is in that brand's own care guide.
• Whether the water will be left to dry. If it will, tap water leaves its dissolved solids on the pane, and NGA rules tap water out for its rinse-left-to-dry method.
• What the makers' steps use instead. They rinse with clean water, clean each window individually with light pressure, and rinse and dry any run-down quickly.

Keeping glass presentable between professional cleanings is a routine of its own, and keeping windows clean between visits covers it.