Cycles of Concentration from Conductivity

COC=σtσm\text{COC} = \frac{\sigma_t}{\sigma_m}

Enter your known values, leave one input blank, and solves for the missing one. Try different units for next level excitement!

Learning zone

Nobody meters makeup and blowdown on a routine service call — they dip a conductivity probe in the makeup line and again in the basin, and divide. Dissolved salts carry current, they do not evaporate, and they concentrate in lockstep, so 2400 μS/cm in the tower against 400 μS/cm in the city water means the system is running at exactly 6 cycles. The same probe is what the blowdown controller uses: set a 2400 μS/cm setpoint and the solenoid opens whenever the basin drifts above it.

Two traps catch people. First, conductivity meters are temperature-compensated to 25 °C — a hot basin and a cold makeup tap read on different bases unless compensation is on, and a 10 °C error is worth roughly 20% on the reading. Second, if you dose an acid or a conductive inhibitor, that chemical shows up in the tower reading but not in the makeup, inflating the apparent cycles; that is precisely why many programs cross-check against a non-reactive tracer such as chloride.

Cycles of Concentration from Conductivity
COC=σtσm\text{COC} = \frac{\sigma_t}{\sigma_m}
Where
  • COC\text{COC}= Cycles of concentration
  • σt\sigma_t= Tower water conductivity
  • σm\sigma_m= Makeup water conductivity