The worst thing I'm still finding is I'm still,after 6 odd months,getting white dots at the top of frames.It's not dirt I've missed,it's in the spots of water that is left after I've rinsed,but just at the tops.TDS is 000 and the rest of the windows generally seem fine.Spoke to a very experienced chap I bought some gear off and he said there is naff all you can do about it.I trad downstairs windows now because of it so at least I can be assured the downstairs is tip top.As a side note,I've never had a single complaint about wfp results though.