[windowwashers]

i dont have a clue what fluid dynamics are
BUT imo it snags the blade if you use it pure for trad

it does because there is no crap in it to give slide, use gg4/3 gives a little better slide takes a little getting used to IMO

personal pref i spose ian but i have a two year old bottle of gg and i hate it
squegee off for me
or even tfr,that really slips

each to our own I guess  , i hated gg4 when i first started as it kept catching, but got used to it, i have loads of squeege off mybe i used try that next time im trad  :

[Sanity]

If soft water (low TDS) is so bad for removing soap from things, how come it is so good at removing soap from windows?

To rais the TDS of water, you just add desolvables.  anything from salt / sugar to bicarb, soap, dirt, basically anything that will dissolve.

[*Mr Tumble]

Soap from glass is one thing, soap from hair/hands is another.

[steven ainger]

if you want some hard water come and see me in essex, my tds averages around 500 but last summer it rose to 600,

[*Mr Tumble]

Got mine up to 550 odd this morning which I'm pleased about.

Not sure what to do with it thou.

I added some bicarb of soda to it.