Choose between DPD colorimetric, FAS-DPD titration, and test strips for pool service water testing based on accuracy needs

Steps

1. Use standard DPD colorimetric testing (comparator or photometer) for routine free/total chlorine and pH checks within its normal reading range, since it's fast and adequately accurate in-range
2. Switch to FAS-DPD titration whenever free chlorine is expected to be elevated (e.g., after shocking or during hyperchlorination), since standard DPD color can bleach out at high chlorine and read falsely low
3. Use FAS-DPD or a lab-grade method when precise documentation is needed for compliance records, since it gives a numeric titration result rather than a color-match estimate
4. Reserve test strips for quick field spot-checks or customer-facing convenience, not as the primary record-of-compliance method on commercial routes, since strip color-matching carries more subjective read error
5. Cross-check readings periodically with a second method to catch instrument or reagent degradation, and replace reagents/strips before their expiration date