# Quick Q: Compressive Fittings **URL:** \ **Category:** Factual Questions\ **Created:** [December 7, 2021, 12:08am UTC](https://boards.straightdope.com/t/quick-q-compressive-fittings/955598 "2021-12-07T00:08:57Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![Jinx](https://avatars.discourse-cdn.com/v4/letter/j/c6cbf5/32.png) [@Jinx](https://boards.straightdope.com/u/Jinx)\ **Post date:** [December 7, 2021, 12:08am UTC](https://boards.straightdope.com/t/quick-q-compressive-fittings/955598/1 "2021-12-07T00:08:57Z")
My fridge’s water line broke at the compression nut fitting. I bought a new fitting, but how far from the end of the (1/4-in) copper tubing should the ferrule be placed? ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [December 7, 2021, 12:23am UTC](https://boards.straightdope.com/t/quick-q-compressive-fittings/955598/2 "2021-12-07T00:23:24Z")
Around 3/16” The easiest way is to slip the ferrule on, then insert the tube into the fitting. The tube will bottom out, and push the ferrule to the correct position. ---
**Author:** ![Jinx](https://avatars.discourse-cdn.com/v4/letter/j/c6cbf5/32.png) [@Jinx](https://boards.straightdope.com/u/Jinx)\ **Post date:** [December 7, 2021, 1:45am UTC](https://boards.straightdope.com/t/quick-q-compressive-fittings/955598/3 "2021-12-07T01:45:05Z")
Oh, I thought the ferrule’s purpose was to block the fitting from slipping off the tube, no? Thus, I thought the fitting slipped on first and then the ferrule slipped on with the tapered end pointed toward the fitting. ---
**Author:** ![Princhester](https://avatars.discourse-cdn.com/v4/letter/p/3e96dc/32.png) [@Princhester](https://boards.straightdope.com/u/Princhester)\ **Post date:** [December 7, 2021, 2:02am UTC](https://boards.straightdope.com/t/quick-q-compressive-fittings/955598/4 "2021-12-07T02:02:26Z")
I think there might be some confusion between you and **beowulff** about what you mean by “fitting”. I may not be familiar with the type of connection, but usually the purpose of the ferrule is to seal the joint. It goes between what the tube is going into, and a threaded nut. When the nut is tightened down, it compresses the ferrule and seals the joint. [Like this](https://upload.wikimedia.org/wikipedia/commons/thumb/1/14/Compression_fitting_isolating_valve_15mm_screwdriver_turn.jpg/1920px-Compression_fitting_isolating_valve_15mm_screwdriver_turn.jpg) ---
**Author:** ![Jinx](https://avatars.discourse-cdn.com/v4/letter/j/c6cbf5/32.png) [@Jinx](https://boards.straightdope.com/u/Jinx)\ **Post date:** [December 7, 2021, 3:17am UTC](https://boards.straightdope.com/t/quick-q-compressive-fittings/955598/5 "2021-12-07T03:17:44Z")
Princester wrote: I think there might be some confusion between you and **beowulff** about what you mean by “fitting”. I may not be familiar with the type of connection, but usually the purpose of the ferrule is to seal the joint. It goes between what the tube is going into, and a threaded nut. When the nut is tightened down, it compresses the ferrule and seals the joint. Jinx says: That makes sense to prevent a leak. So, about how far from the end of the copper tubing should the ferrule be placed? I guess it’s not too far from the end. I wager I should first gauge it by placing the compression fitting against (ie, parallel) the copper tubing to see about how long the fitting is along the copper tubing - if you can picture what I mean - before installing the fitting and ferrule. (FWIW, here is a picture of my [exact fitting](https://images.search.yahoo.com/search/images;_ylt=A2KLfR6G0q5h3DkA9xtXNyoA;_ylu=Y29sbwNiZjEEcG9zAzEEdnRpZANEMTA0NV8xBHNlYwNwaXZz?p=compression+nut&fr2=piv-web&type=E211US0G0&fr=mcafee).) It keeps changing positions in the image! It’s a Jones Stephen C74-016, a yellow brass color. ---
**Author:** ![Princhester](https://avatars.discourse-cdn.com/v4/letter/p/3e96dc/32.png) [@Princhester](https://boards.straightdope.com/u/Princhester)\ **Post date:** [December 7, 2021, 3:23am UTC](https://boards.straightdope.com/t/quick-q-compressive-fittings/955598/6 "2021-12-07T03:23:31Z")
You need to link to the specific image not the search page. Anyway, it’s as I thought and as **beowulff** said and goes together in the order shown in my link. Put the ferrule on a little way (3/16" will do it’s not critical) and push the tube in quite firmly, then tighten the nut. The ferrule will find it’s own place as it is squashed by the nut. ---
**Author:** ![Jinx](https://avatars.discourse-cdn.com/v4/letter/j/c6cbf5/32.png) [@Jinx](https://boards.straightdope.com/u/Jinx)\ **Post date:** [December 7, 2021, 3:48am UTC](https://boards.straightdope.com/t/quick-q-compressive-fittings/955598/7 "2021-12-07T03:48:04Z")
Pinchester wrote: Anyway, it’s as I thought and as **beowulff** said and goes together in the order shown in my link. Put the ferrule on a little way (3/16" will do it’s not critical) and push the tube in quite firmly, then tighten the nut. The ferrule will find it’s own place as it is squashed by the nut. Jinx says: Ah! Got it! (This struck me as I went for a snack and thought more about this.) Thanks, all… Sorry, sometimes, the obvious eludes me. I guess I get intimidated by my anxiety and lack of experience, I guess, instead of just taking a step back and thinking it through.