Senders, switches and sensors using a National Pipe Thread
The NPT type tapered thread is used to create a watertight or airtight seal between the threads of the unit and the threads of the cavity it is being installed in to. NPT type threads are not designed to be “bottomed out” or tightened to the end of the threads. Over torqueing or “bottoming out” of the unit can cause major damage to the threads, or breakage of the housing cavity.
When installing units with an NPT type thread, always thoroughly clean the area in and around the threads of the cavity. Use a small amount of Teflon coating or some other appropriate sealer on the threads when installing, do not over apply the sealant. Some units come with sealant already applied on the threads, you should not double up or use more than one type of sealant. Not all NPT type senders or sensors have the same or standard torque specification. Always refer to a service manual for the proper torque specification for the device you are installing as to not cause damage to the part or the mounting cavity.