4731.6220 POOL WATER PURITY.
A pool water purification system must be run sufficiently to maintain the conductivity of the pool water below 20 microsiemens per centimeter under normal circumstances. If pool water conductivity rises above 20 microsiemens per centimeter, a licensee must take prompt actions to lower the pool water conductivity and take corrective actions to prevent future recurrences.
A licensee must measure the pool water conductivity frequently enough, but no less than weekly, to ensure that the conductivity remains below 20 microsiemens per centimeter. Conductivity meters must be calibrated at least annually.