I got a few beers in me so no offence intended !
Listen , if your on RO why cut corners with the TDS readings , imean , your resin must last for donkeys ! , im DI only and i wont opperate with anything less than 000 TDS , my tap TDS is 100 so i get through a bag of resin a month , well i should anyway , but my superior brain has invented a pre filter system which treats 16000 L to 000 TDS per bag of resin , anybody with a calculator will be able to work out that this is 10000 L more than i should be getting !
Anyway stop being so tight and give those customers of yours a bit of value for money ! , and remember , ELMO IS THE KING !
Rich P @ F