I am trying to connect a water filter with regular 3/4" FIP inlet and outlet to regular faucet tubes with 3/8" Compression Type female connectors. So, what I need, I guess, is a pair of 3/4" MIP to 3/8" O.D. Compression fittings.

My search has revealed to be a challenge, as there seems to be an uncountable number of fitting standards in North America, and a variety of labelling conventions for each type.

I have not been able to find any 3/4" MIP to 3/8" O.D. Compression fittings, but there seems to be many 3/4" MIP to 3/8" O.D. Tube fittings on the market. Are these two the same? And if yes, what is the difference between Tube and Flare fittings?

A link to the appropriate fitting would be a great help as well.

P.S. Are these the right fittings: (1|2|3)? How can I find/order them in Canada? It seems impossible to nail down the search on Homedepot website.

  • 1- NO

  • 2- NO

  • 3- YES!

Swagelok fittings are different than compression fittings and will not work. Both are very different than flare fittings, which have a tapered nut and require the tubing to be formed in a "flared" taper at the end (using a special tool) and do not use a sleeve (ferrule). They also use a different thread:

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You may find that regular compression fittings are labeled "tube" fitting in your locale. Home Depot Canada has them, they include a brass insert (for plastic tubing) and ferrule (for all tubing applications; for your purpose do not use them.

enter image description here Why don't you take your connectors down to the local mom & pop plumbing / hardware shop instead of going to the "big box", they likely have the part and will be full of good advice as well.

here's the link to the part at HD: 3/8 comp. x 3/4 mip adapter


Typically, we would use a reducer to reduce down from 3/4" FIP to a 1/2" FIP, (3/4" MIP x 1/2" FIP reducer) but this is not necessary if your can find a 3/4 MIP x 3/8" Comp fitting.

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Then we would use a 1/2" x 3/8" compression adapter.

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If you have plastic tubing, purchase and use a delrin sleeve instead of the brass compression ring.

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