Thanks for all the replies guys, very helpful and useful information.
Especially chris with your video about brushing excess water from the rubber seals so they dont drip? That is the purpose of your technique isn't it?
So today guys i had the exact same problem, this time no wooden windows involved at all just UPVC.
So i upped the flow rate, spent even more time cleaning and rinsing and here is an example i want to give you to prove that it could not be anything other than the rubber seals causing the spotting.
I cleaned 2 bungalows next door to eachother. First bungalow, had what i call recessed rubber seals, they dont really protrude at all or leak or drip, so you can just WFP them really quick and blast the dirt off, rinse thoroughly, and you really never need to worry about spotting. Today this bungalow i did, the frames were filthy. I blasted them all over did the frames openers and main windows below all in one go, hoping to expect some spotting. Nope they were 100% perfect as they always are on these type of seals.
Bungalow next door, totally different results. The frames were not even dirty, neither was the glass. These windows had all what i call Flat Edge rubber seals, the ones that protrude and in lots of cases can leak out as they degrade over time. I cleaned all the top frames then rinsed. Then cleaned the openers and rinsed inc middle bar. Waited around 2 mins before i then cleaned window below and rinsed from about 1/2 inch below the rubber seal. The problem was even on a hot day these seals drip for ages, literally like upto 20 minutes or more.... I cleaned all the windows the same way, and atleast 1/4 of them had spotting and streaks down them. Same thing happened today on around 5 other bungalows with exactly the same rubber seals.
So my point is here, surely it can't be that my technique is wrong or that i am personally doing something wrong, it must just be that the rubber seals are bad and leak and drip, which is causing all of the spotting.
I can't see any other logical reasoning for it... I spent 45 minutes cleaning a bungalow which is priced at £10 and i still got spotting on 3 windows.... I mean cmon, i can't get any slower and be more thorough even if i wanted too....
Please see attached photos of the types of rubber seals im talking about.
Let me know your thoughts about this. I have another full day tomorrow cleaning bungalows and i am not looking forward to having to clean more of these protruding seals. It literally knocks my confidence, not knowing whether i am walking away from potentially spotted streaked windows....
Thanks guys!