Hi, ive been using WFP for years and can honestly say that values upto
10 are absolutely no problem, you will get good results upto 20 but
thereafter there will be spotting.
Also did you take this reading at the beginning of work or after letting
it run thru your system for a while; remember that there will always be
higher TDS reading at the beginning of work due to impurities in the Hoses and Jets etc.