O-Rings
O-rings are used throughout a pools plumbing to create watertight seals. You find large O-rings sealing the joints of a filter to small O-rings sealing rotating valve stems. O-rings also create watertight seals around threaded fittings and unions. O-rings are in pumps, filters, heaters, chlorinators, valves, actuators, and unions. Just about anyplace two surfaces come together and has water you will find an O-ring sealing the joint.
An O-ring is a doughnut shaped ring molded from an elastomer.
The basic core polymer of an elastomeric compound is called a rubber, produced either as natural gum rubber in the wild, on commercial rubber plantations or manufactured synthetically by the chemical industry.
Swimming pool pump and filter o-rings are typically made with EPDM rubber, while chlorinator o-rings are usually made of a Fluorocarbon, Viton or FKM. Many O-rings we see in pools are Buna N 55 hardness. Buna is one of the most widely used O-Ring elastomer compounds and is a Nitrile compound. The actual name is Acrylonitrile-Butadiene and can be referred to as Buna, Nitrile or NBR. Buna has heat resistance up to 212F (100C) and cold flexibility down to between -30F and -70F depending on compound.
For more details about O-Rings see the Parker O-Ring Handbook
O-Rings? O-Yeah! How to Select, Design, and Install O-Ring Seals is a great video about O-Rings.
O-Ring Wear and Tear
O-Rings may last 5 to 10 years, they don't last forever. O-Rings will often wear out and need replacement before the equipment does.
Ozone, weather and atmospheric aging can make O-Rings brittle and lose their flexibility. O-Rings in rotating shaft seals in pumps, valves, and actuators can wear from the friction of the shaft movement.
If a threaded joint develops a drip suspect that an O-Ring needs to be replaced.
O-ring leaks on the pressure side of the pool equipment will leak water when the pump is running and suck air in when the pump shuts off.
O-ring leaks on the suction side of the pump will suck in air when the pump is running and may squirt water out when the pump shuts down. The pump basket O-ring under the pump lid and the pump drain plug O-rings are on the suction side and can create suction side air leaks.
When inspecting an O-Ring look for:
- small cuts, nicks or gashes, typically from installation damages.
- ragged edges which appear tattered, typically due to excessive clearances.
- blisters, pocks, or pits on its surface, due to rapid pressure changes.
- radial cracks located on the highest temperature surfaces. In addition, certain elastomers may exhibit signs of softening due to exposure to excessive heat.
- signs of degradation including blisters, cracks, voids or discoloration, due to chemical incompatibility.
- circumferential splits within the flattened surface, usually due to excessive compression.
- a flat surface parallel to the direction or motion. Loose particles and scrapes may be found on the seal surface, due to friction from a rough sealing surface.
Below is an O-Ring that was nicked and damaged:
O-Ring Sources
Check the Installation Manual for your equipment to find the manufacturers O-Ring part numbers.
Many O-rings are a commodity and can be found at hardware stores for much less then when packaged by a pool company. The advantage to paying pool company prices is you know you are getting the correct size O-Ring with the required materials.
O-Rings, Inc. is a leading online supplier of quality O-Rings.
allorings has a O-Ring Size Chart - AS568 Standard O-Ring Sizes that finds AS568 o-ring standard sizes by cross section, inside diameter and outside diameter in their O-ring size chart and separate O-ring tolerance chart.
Aladdin Equipment Company, Inc. makes many of the O-Rings and GO-KITs manufacturers use. Note that Aladdin has their own proprietary O- numbering standard for O-Rings that is different then the AS-568 standard.[1] Aladdin has a Parts Cross Reference on their website.
Tightening O-Rings
O-rings sit in a groove (or gland) and seal through compression. Any joint sealing with an O-ring should not be over-tightened. Over-tightening an O-ring joint can deform the O-ring and lead to leaks. Generally, fittings with o-rings only need to be "hand tight." You might need a wrench to loosen such a fitting, but you shouldn't use a wrench to put it back together if you can avoid it. If your hands are not strong enough to tighten a fitting enough, then you can gently use a wrench, but only to make the fitting a bit more snug than you could with your hands. You don't crank the fitting down.
If a fitting with an O-ring is leaking do not simply crank it down to try and stop the leak. That can crack the union, or pipe, or further deform the O-ring. Open up the joint and examine the O-ring for nicks, cracks or deterioration. Replace the O-ring if it is damaged or has lost its flexibility and is deformed.
Below shows a filter drain plug that was overtightened and the O-ring deformed:
O-Rings Need to be Lubed
All O-rings seal better when Pool Lube is used on them. Pool Lube should be used on all new O-rings and small leaks can often be stopped with an application of Pool Lube.
O-ring lube allows the three surfaces involved (the O-ring and the two components it's sealing together) to slide together as you tighten things up.[2] Without it, the O-ring will pinch and bind and deform. It's the deformation that causes the leaks. And the premature wear. So the lube is not really adding to the sealing properties of the O-ring, rather it allows the O-ring to retain its correct shape and do its job. And in that way it can lengthen the O-ring's life. Cleaning the O-ring and the surfaces it touches is important because a chunk of dirt can also deform the O-ring and cause a leak.
Any rubber gasket you use should always have silicone lube applied unless expressly forbidden by the manufacturer. Rubber gaskets are imperfect and there will always be a difference in size and shape between the groove they sit in and the gaskets dimensions. Lube is necessary to make up those imperceptible differences and to create a watertight seal. Lube also adds a layer of material that protects the rubber from damage by water and chemicals.
