[NWH]

I do a large Housing Association contract where all the windows are pvc and nice to do with the pole i`ve given them about 4-5 cleans wfp and the results are good,but i`ve noticed today that quiet a few of the windows that i was about to do had 2-3" of spots at the bottom of the glass.The rest of the glass was perfect and i always scrub and rinse well especially this part of the window,it`s weird the glass sheets and then beads up at this 2-3" at the bottom of the glass does anyone else have this same problem and if so whats the best way to get round it,please don`t say rinse rinse rinse cos i`ve already tried that.

[Fivestar Cleaning]

I'm not very experienced at this yet but it sounds to me like contaminated water is dropping on to the sills from above and  splashing the bottom of the windows.

[Russell Macdonald]

There was a thread on this last year. I had noticed this too on the odd window.

Ian or Tosh, i cant remember who ( i think it was Ian as hes the pro of the 2  ) said to give it an extra scrub along the bottom, i do it all the time now & i've had no more probs.

Macc

[Sir Squeaky]

I had a bit of trouble with this at first.

I just realised you have to rinse all the way down.
I rinse from the top and now I follow the water down too.

[davidpitts]

I have had a similar problem on a few jobs. I think what is happening is after the water has run down the glass in a sheet, it breaks up into lots of seperate trails on the bottom few inches and as the trails are drying they are pulling dirt up from the bottom seal, I think its called capilliary action, I give the seals a good scrub and this seems to be making them get better over a few cleans. On the downstairs windows I have given some of them a quick wipe with a microfibre on first few cleans

[JM123]

just check your tds as well.  Had a small prob with this last summer and it turned out to be tds level (had risen to 4ppm) and as we work very fast this was leaving very faint spots at the bottom of a few windows.  Changed resin and all was good again.

[Jeff Brimble]

It may have  a coating all over the glass, you will find that the sides tend to spot as well, just that gravity pulls them downover each other faster. The bottom few inches will have a slight concentration of any minute tds. On properties that become a problem I find its best to go back after 5 min and flash rinse the bottom 3" again. They may still slightly spot.
You will often notice the same effect on timber windows where the glass sides have been silicone beaded in. The silicon spreads by capilliary action creep and can cause a band of silicon for 3" all round the edge of the glass. Its there forever because its been absorbed into the micro structure of the glass.

[NWH]

My tds is 001 after RO from a static tank and then goes through resin in the van so it`s not the water.

[Jeff Brimble]

000 tds will still leave milky spots on some Hphobic glass.
 You get to a point where you have to accept it. 
Anybody tried 0000tds water, if there is such a thing ?

[JM123]

tds is quite an inaccurate way of testing water quality anyway, all it sums up is the total dissolved solids, there are other VOC's etc left in the water (as no ro is 100% efficient).

If you really want to make sure your water is super pure then try testing it with a micro-siemens tester.  1ppm is nominally 28micro-siemens.

[Bazzy1999]

micro-siemens tester ? 

[NWH]

Where can you get them from.

[Jeff Brimble]

Quote,
"1ppm is nominally 28micro-siemens"

So is distilled water zero ? When does the water become free of contaminants. I know that most ROs work down to 5 microns.
Should we be looking for lower tds  than 000 ?   and would this then dry spot free ?