Pool O Rings are one of the most popular seals used in pool equipment because they are inexpensive and easy to make, reliable, and have simple mounting requirements. They can seal many thousands of pounds of pressure. Successful o-ring joint design requires a rigid mechanical mounting that applies a predictable deformation to the o-ring. This introduces a calculated mechanical stress at the o-ring contacting surfaces. As long as the pressure of the fluid being contained doesn’t exceed the contact stress of the o-ring, leaking cannot occur.