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How to connect 1/8 inch tubing to a Restek gas regulator

9 May 2013

Because the majority of gas regulators which Restek sells are designed to connect to 1/4 inch tubing, we (tech service) frequently get asked which additional fittings are needed to connect to 1/8 inch tubing. This post will summarize which additional fittings are needed to accomplish this task.

First, let me explain which gas regulators I will be discussing in this post. They can be manufactured of either chrome-plated brass or stainless steel, they can be single or dual stage, and they will have a specific CGA (Compressed Gas Association) fitting on one end. The other end will be a 1/4 inch MNPT (male National Pipe Thread) fitting, which screws into the shut-off valve on the regulator. The outlet end of this fitting is 1/4 inch compression, which can connect to 1/4 inch OD (outside diameter) tubing. This fitting is shown by the red arrow in the photo below.

gas regulator

In order to use 1/8 inch tubing with these gas regulators, you have two options:

1. Leave the end-fitting (shown by the red arrow) attached to the regulator and install a tube-end reducer to this end fitting. If you have a chrome-plated brass regulator, use Restek catalog number 23129. If you have a stainless steel regulator, use 23179.

2. Because this extra fitting can be an additional source of leaks, some customers would prefer to remove the current end fitting and replace it with one that has a 1/8 inch compression outlet. The catalog numbers for these male connectors are 23136 for brass and 23186 for stainless steel. When replacing the end fitting, don’t forget to use PTFE tape. Restek PTFE tape catalog number 22486 is commonly used for brass fittings and 22487 for stainless steel fittings.

Note: If purchasing one of our Silcosteel regulators, don’t forget to purchase treated fittings and treated tubing.


I hope this post clearly explains which fittings you will need in order to connect one of our gas regulators to 1/8 inch OD tubing. To read more about fittings, please review my previous post I need a fitting, but which one?   If you are looking for the appropriate gas regulator, review my post Need some help in choosing the correct gas regulator?

If you have any questions, give us a call. Thanks for reading.