One wrong move with a tablet chlorinator can leave you coughing, gagging, and wondering what just hit you. We break down the Pentair Rainbow Chlorinator from a pool service pro’s point of view, including the safety habits that matter most when you open the lid and discover trichlor tablets that never fully dissolved.

We talk through the two common setups you’ll see on equipment pads: the offline Pentair Rainbow 300 series with black tubing and the inline Rainbow 320 series plumbed into the return line. You’ll learn how each style behaves, why placement after the heater is non-negotiable, and how small issues like trapped air or residue under a screen can turn into poor chlorine output and nasty fumes. We also get very clear on the biggest chemical compatibility rule in pool maintenance: these feeders are for trichlor tablets only. Cal-hypo in a trichlor chlorinator, or mixing residue between them, can create a dangerous reaction.

From there, we go hands-on with the fixes that keep these units running for the long haul: the offline check valve elbow that clogs and stops flow (and why replacing it beats trying to clean it), the stuck lid caused by a swollen O-ring, and the tools and lube that make servicing safer and faster. 

• why the Rainbow chlorinator is a practical choice for pool service work
• why trichlor tablets only and why cal-hypo can cause an explosion
• offline 300 series vs inline 320 series and what tends to fail on each
• correct chlorinator placement after the heater to prevent corrosion damage
• how to open the lid safely and avoid toxic fumes when tablets are undissolved
• the offline check valve elbow as the main clog point and the R172061 replacement
• how to purge air on inline units and clean the bottom screen
• stuck lid causes, swollen O-ring diagnosis, and the R172009 replacement
• using large channel locks and lube to remove and prevent seized lids
• black tubing brittleness, leak risk, and replacing both lines with R172023
• stocking a rebuild kit R172064 and other spares to avoid being stuck mid-route

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