That resin does seem to have gone off pretty quick for 88ppm. When i was di only the water i was using was about 55ppm, and while it could go off quick, i wouldn't expect it to go to any more than about 20ppm during the course of a day (and that is only if i didn't notice, if i did, i would have changed it at 10ppm!). Until such times as you can get yourself an r/o system, you will just have to be extra vigilant with your tds meter!.