Water Conditioning (C-55) · Lesson 5 of 5

Chlorine Disinfection: Dose and Safety (CPC 609.10)

"Chlorine Disinfection: Dose and Safety (CPC 609.10)" is lesson 5 of 5 in the Water Conditioning (C-55) Learning Hub. It opens with "When Disinfection Applies" and works through 6 short steps, then a worked example you can check yourself against.

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Steps in this lesson

  1. When Disinfection Applies
  2. The Printed Sequence
  3. Turn Percent Bleach Into ppm
  4. Know the Exposure Limit for Chlorine
  5. Eyewash and Storage Rules
  6. Spills and Chemical Containers

The worked example in the course applies this lesson to a realistic job in 6 steps, from "Flush first" through "Check worker exposure while pouring and flushing".

What you'll be able to do

  • Explain the main idea of "Chlorine Disinfection: Dose and Safety (CPC 609.10)" in plain language you can use on the exam.
  • Apply this step with confidence: "Turn Percent Bleach Into ppm".
  • Apply this step with confidence: "Know the Exposure Limit for Chlorine".
  • Apply this step with confidence: "Eyewash and Storage Rules".
  • Apply this step with confidence: "Spills and Chemical Containers".
  • Test yourself on the worked example and the quick-check quiz inside the classroom.
Chlorine Disinfection: Dose and SafetyCPC 609.10 DISINFECTION SEQUENCE1. Flush with clean potable water2. Fill, valve off, let it stand:200 ppm for 3 hours, or 50 ppm for 24 hours3. Flush until the chlorine residual doesnot exceed the flushing water residual4. Repeat if a bacteriological testshows contamination persistsBLEACH DOSE (C1 x V1 = C2 x V2)Assumed: 120 gal system + tank, 6% bleach6% = 6 x 10,000 = 60,000 ppm200 ppm for 3 h120 x 200 / 60,000 = 0.4 gal= 51.2 fl oz50 ppm for 24 h120 x 50 / 60,000 = 0.1 gal= 12.8 fl oz128 fl oz per gallon8 CCR 5155 Table AC-1, chlorine: PEL 0.5 ppm (8-hour TWA), STEL 1 ppm (15 minutes)8 CCR 5162: eyewash within 10 seconds of the work; hoses and sink faucets do not count8 CCR 5164(a): store acids and oxidizing agents apart; never mix themTWA = (C1 T1 + C2 T2 + ...) / 8, using 8 hours as the divisor (8 CCR 5155 Appendix A)200 ppm for 3 h in 120 gal = 0.4 gal (51.2 fl oz) of 6% bleachThen flush until the residual is no higher than the flushing waterSource: 2025 CPC Section 609.10; 8 CCR 5155, 5162, 5164. Bleach strength and volume are assumed.CC
The diagram for this lesson, exactly as it appears in the Learning Hub.

The first steps of this lesson

Step 1: When Disinfection Applies

CPC Section 609.10 says new or repaired potable water systems shall be disinfected prior to use where required by the Authority Having Jurisdiction, and the method followed is the one prescribed by the Health Authority or, if none is prescribed, the sequence printed in 609.10. The CSLB C-55 study guide lists disinfection under troubleshooting, maintenance, repair and replacement, so expect to disinfect piping and equipment you install or open up.

Step 2: The Printed Sequence

CPC 609.10 prints four steps. First, flush the system with clean, potable water until potable water appears at the outlets. Second, fill the system or part of it with a water-chlorine solution of not less than 50 parts per million, valve it off and let it stand 24 hours, or fill it with not less than 200 parts per million and let it stand 3 hours. Third, flush with clean potable water until the chlorine residual in the water coming from the system does not exceed the residual in the flushing water. Fourth, repeat the procedure where a bacteriological examination by an approved agency shows that contamination persists.

The remaining 4 steps, the worked example and the quiz are in the course. This is a preview. The full lesson, with the step-by-step explanations, a worked example and a quick-check quiz, is inside the classroom.

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