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How an Inline Chlorinator Works

Your inline chlorinator is a small but very significant piece of equipment. It is called a Tri-Chlor chlorinator because it uses trichlor tablets to help maintain safe, clear water for your swimming enjoyment. The purpose of this article is to describe the components and function of your inline pool chlorinator.

Two Different Types of Tri-Chlor Chlorinators

In-Line Automatic Chlorinator

This type of chlorinator is called “in-line” because it actually plumbs into the return line of the pool. The Rainbow 320 is a good example of this. There is a scoop that picks up water out of the return line and pushes it up into the chlorinator. The water then exits through the bottom of the chlorinator into the return line.

Off-Line Automatic Chlorinator

This is called “off-line” because it stands on the ground and has hoses that lead too and from the plumbing. The Rainbow 300 is a good example of this. The intake hose taps into the line between the pump and the filter, and the outlet hose taps into the line after the heater. It takes advantage of the pressure differential created by the filter.

The Basic Components of an inline Tri-Chlor Chlorinator:

Control Valve

This governs the flow of water into the chlorinator and thereby controls the chlorine feed rate (to a certain extent).


This is a tube that holds the tablets. It is sized for a three inch tablet but also can be used with one inch tablets, but they dissolve much more quickly

– use ONLY trichlor tablets in this chlorinator. Do not put granular chlorine or any other type of tablet or any other chemical in this chlorine feeder. It can create an explosion and result in serious injury and equipment damage.


This is the top cap that screws on. It has an o-ring that should be changed every 6-12 months. The strong chlorine tends to dry out this o-ring fairly quickly.

Check Valve

There is a check valve in the bottom of the chlorinator which helps to keep water from backing up through the chlorinator into the rest of the equipment. This has limited valve.

Every chlorinator should have a full sized check valve installed upstream of the outlet port, especially if if there is a heater in the system. It needs to be a corrosion resistant Rainbow check valve and not some other type of check valve.

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