Also agree that you can clean with water above zero.
Never understood this thinking.
The basicS of getting the glass clean is to use pure water with oo TDS, so why would you want to use higher and risk doing a rubbish job ?
No the basics of wfp cleaning is to use water that doesn't leave any traces on the glass after it dries, 00tds is just a measure
of conductivity and one that we have been told to use as a rule of thumb.
Doesn't mean you cant go above it without ricking the quality, I have cleaned my own property with a TDS of 10 then examined
the glass very carefully in full sun without seeing a single spot or water mark.
So I now let my TDS go to 10ppm before changing the resin, any less and I'm just throwing away usable resin/money.
I'm not saying you cant go above 10ppm but that's where I have tried it to.