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Many customers are confused by how bulkhead fittings are sized. The two many dimensions that they need to know are the interior thread size and the hole size.

- The interior thread is what the fitting is called out by. For instance a 32182 1/2" bulkhead tank fitting has 1/2" FNPT on the inside.

- The hole size is basically the diameter of the external threads. You need this because that is the size hole that you will need to cut out of your tank. The hole sizes for most of our bulkheads can be seen by clicking here.

Please note that the male thread is not designed to have anything other than the nut connected to it. It is usually never a standard size thread.
The only way to connect something to this is to use the internal female threads.  

The nut should go on the outside of the tank.
For fittings with one gasket, the gasket goes inside the tank. For fittings with two gaskets, one goes inside and one goes outside.

Title: How are bulkhead fittings sized?
Description: How to determine what size bulkhead fitting you need.
Published: 5/10/2011
Last Edited: 9/18/2013
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