I don’t know of anything you could put in your tank that will consistently produce better rinsing off glass with hard water (maybe @CaCO3Girl could chime in on the topic). Experimenting with different surfactants may help. I find that Elemonator rinses much more nicely than other “otc” soaps I used in the past.
Your best bet if you already have an RO/DI system & WFP, I believe, is to upsell a “pure water scrub & rinse” along with screen washing. Depending on the job, I’ll get between $3-$8 per window for this service.
I let the customer know that power washing has a tendency to spot up the windows, and the scrub & rinse will leave them 99% clean in most cases. I don’t sell it as “window cleaning” unless I will be cleaning insides as well, and can inspect for drip marks or missed gunk.
If the customer opts for this added service, I request that they remove all the window screens ahead of time and stack them in a central location. I wash them while I’m doing the housewash, and they take maybe 10-15 seconds per screen. The rinse & scrub is maybe 45-60 seconds per pane.
So I feel like the customer and I make out really well on the deal. Say they get a housewash on a small home with 15 windows. Depending on difficulty, I may tack on $50-75 for the scrub and rinse service. That takes me 20-30 minutes extra, so I’m still hitting my goal of $150/hr, and not spending any gas or chemicals to do it; just a negligible amount of DI resin. And the windows come out just as clean or cleaner than they could do themselves, in most cases.
Had they called me just to clean the exteriors of 15 windows without any power washing, I would have informed them of my service minimum of $225. But even if they got around that somehow by getting a neighbor to sign up or something, I would still charge close to $150 to clean them by hand, since it would be a first time clean on nasty windows and screens, and could take 1.5-2 hours.
While your comment is well intentioned, and I think we all should feel impelled to support this site however we can, I just want to point out what one of the founders, @Chris had to say on the topic:
And further comments:
But I think that @Alex made some really great counter arguments of why the average window cleaner or pressure washer shouldn’t try to DIY an RO/DI system. Some have done it successfully, but the time investment often outweighs any savings. The old adage, ‘tripping over dollars to pick up pennies’ comes to mind.
