Application Note Thread Sealing and Engagement

In order to create a properly sealed environment, care must be taken to properly thread and seal your float switch. Here are a few words of advice to assist you. Always be sure to consider the thread engagement or mounting type when selecting your actuation levels.


  • Gasket and seal materials should be selected with both fluid and environmental considerations in mind. Be sure to use the proper torque for the selected fittings. Excessive torque is the most common cause of seal failure.

  • NPT threads are tapered threads designed to compress for a waterproof, pressure tight seal. To insure proper thread fit and seal a TeflonT tape or compatible thread sealant should be applied to the threads before installation. The proper torque should be applied using the following guidelines;

    • Plastics NPT - Install the threads till hand tight, than using the proper wrench, tighten the hex an additional 3/4 to 1 turns. Be careful not to over torque. If leaking appears, increase by 1/4 turn at a time until proper seal is created.

    • Metal NPT - After applying a thread tape or sealant, start the threads by hand, then tighten until approximately 3 to 4 threads are engaged. If leaking appears, increase by 1/4 turn at a time until proper seal is created.