Here is a complaint we hear constantly: "I replaced the chlorinator lid o-ring last spring and it's already hard and cracked." The seal is not defective. It is the wrong elastomer for the job.
Why a chlorinator is the harshest place in the system
Everywhere else in a pool, chlorine is diluted to a few parts per million. Inside a chlorinator or chemical feeder, the lid o-ring sits directly above concentrated tablets and the aggressive gas that comes off them. The concentration at that seal is orders of magnitude higher than in the water.
Buna-N nitrile is a fine general-purpose material — it is what we recommend for pump housings, filter tanks and most of the system. But it has poor resistance to strong oxidisers. In a chlorinator it hardens, loses elasticity, then cracks. One season is typical.
FKM is the correct material here
FKM fluorocarbon resists strong oxidisers and holds its elasticity in exactly the conditions that destroy nitrile. It costs more per ring and lasts several times longer in this specific application.
This is the one place in a pool system where paying more for material is unambiguously the right call.
FKM chlorinator o-rings we stock
- Pentair R172009-V Lifeguard chlorinator lid FKM o-ring
- Rainbow R172009-V Lifeguard chlorinator lid FKM o-ring
- Hayward CLX200K chlorinator FKM o-ring
Note that Rainbow and Pentair list the same R172009-V part — Pentair acquired Rainbow, so both numbers refer to the same seal. Either listing gets you the right ring.
A note on the trade name
You will often see this material called by a well-known brand name. FKM is the correct generic designation, the same way nitrile rather than a brand describes Buna-N. Both refer to the polymer family, and what matters for your chlorinator is the chemistry, not the label.
Lubricate, but choose carefully
Silicone lubricant extends the life of a chlorinator seal by keeping it supple. Use a proper food-grade silicone — petroleum greases attack elastomers and have no business anywhere in a pool system.
Full material comparison in our o-ring material guide.
Before you reassemble
Seat every o-ring with a thin film of food-grade silicone. Dry rings pinch, twist and take a set — the usual reason a brand-new seal weeps within a season. Aqua Flex Food Grade Silicone Lubricant is what ships in our kits.
O-rings only. Never lubricate the polished faces of a mechanical shaft seal.
Beaver Island Parts Company is not affiliated with, endorsed by, or sponsored by any equipment manufacturer named on this page. All brand names, model numbers and part numbers are the property of their respective owners and are used solely to identify the equipment our replacement parts fit.