Spots on windows

Please can you help, a customer sent me this photo, just the bottoms of the windows are leaving white spots, I'm using pure water and giving them a good rinse, although with these windows when you rinse near the bottom of the glass the water sort of runs back up the windows, it's really strange, not sure what to do about it? Any help would be greatly appreciated. thanks 

Sure its not old water stains that were there before?

If not id suggest giving the bottom part a good scrub and a better rinse. Also maybe turn the flow down as you may be splashing dirty water from sill back into the glass. 

I had a similar problem recently. I was cleaning the sill and bottom of the frame, after I had rinsed, subsequently catching the bottom of the glass with my brush. Thankfully she pointed it out, otherwise I'd have had no idea...

I can't really see if those spots are still wet? Looks like hard water staining to me if the glass is dry. Do they have hanging baskets near the windows?

Looks like calcium build it to me, not the spots that can sometimes occur throught wfp. If you can reach it safely spray some viakal on to an applicator give the are a good rub leave for 20 seconds then wfp as usual. This normally works a treat for me, however depends on how long the staining has been on the window for.

Looks like stains rather than left over from your wfp mate. As others said maybe hanging baskets or I do a lot of navy married quarters housing and above Windows they have a lead strip like a lintal and over the years the residue dripping stains glass just like that it's a pain

I also find on some houses that the windows aren't set into the brick work or rendering as it is in other houses. Therefore hard water then drips off the wall straight on to the window. I have used Kilrock limescale remover and given it a light scrub then trad the windows. If you do this the first time then you shouldn't need to do it again, or for a long time at least. As mentioned before, it does look like hard water marks and not a WFP problem, unless your TDS is too high? 

Yep that looks like hard stains to me so won't be your pure water unless you're running it at a stupid TDS.

Could well be splashes up from a hose or sprinkler.  I constantly tell people to wipe their windows and doors down in the summer after they water (or be more bloody accurate!) so they don't try to blame me.