What is the upper level that you will let an RO run at (uS) and what brought you to that decision?
I ask as the upper limit on our Aqua Uno units is 150uS which seems very high to me.
If I was in a patient's home and I saw a conductivity over 10uS I would be thinking about remedial action personally although I have no science to this decision - only what our Mancunian forfathers passed on!
Wow you must have some good incoming water. Must be why northerners are so famed for their good health and longevity.
Most ROs here run between 9 and 15uS. We tell patients to let us know when cond. is around 25uS.
When we didn't use softeners (only started using them recently) we found that the pure water Calcium levels were exceeding the limits, sometimes significantly, when cond. got to ~30uS
I download the public water quality reports for each WSZ (Water Supply Zone). All our units and patients are in very hard water zones so we are fitting softeners everywhere now. Didn't seem to matter as much with non heat ROs but the Centurion Heat system definitely doesn't like hard water. Many patients were not citric rinsing as often as they were supposed to.
Most home and unit supplies are 600-800 uS and hardness is seldom less than 300mg/l CaCo3
Similar to you Ian, our limit seems to be historic with no evidence that I am aware of. Here we set water quality alarms at 50us but ask the home patients to inform us if conductivity rises above 20us when we would consider replacement.
We no longer provide softeners to patients since moving to a minimal installation process. Current inlet water conductivities at <400us with hardness of around 170ppm