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Recently I bought a copper water canister/ water bottle for a project I'm doing.

Copper water bottle

I'm looking to use it to replace an inline filthy broken stock water-reservoir in my Samsung fridge. My fridge has a 5/16 LLDPE tubing connecting to it providing water (inlet) and a 1/4 LLDPE tubing connecting to it (outlet). Both of these are push-to-connect fittings. I'm looking to equip this copper canister with push-to-connect fittings and use it instead of the OEM plastic water reservoir.

I'm aiming to use 3/8 outer-diameter push-to-connect fittings for both IN/OUT flows. I'll then run 3/8 tubing to the back and bottom of the fridge and use reducers to 1/4 and 5/16 (which I've already purchased). Of the two fittings I need to put on the bottle, one fitting will be very easy because I can drill in at the bottom of the bottle (which is just plate copper). I'm planning on drilling in with stepped drill bit, and putting on a 3/8 push-to-connect through-wall bulkhead fitting on it. There is only enough room on the bottom for one fitting, and I don't want to tap into the top because I feel like that will compromise the structural integrity of the copper top which is needed when closing the bottle.

While I'm open to any input, the other fitting I'm wanting input on. How can I mount a 3/8 female push-to-connect to the side of a cylindrical bottle. My concern is that if I drill into the side of a cylinder I won't be able to torque the side of the bottle enough to make a water proof connection. These fittings are just plastic. And if I drill into the side of a cylinder and flatten it out afterward, I assume the geometry of the hole will no longer be what I'm expecting (the hole will warp). What ways are there to create a through-wall water proof connection to the side of a cylinder?

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  • $\begingroup$ Why would the top be weaker than the bottom? is it any thinner? Installing those bulkhead fittings on the side seems like a bit of a ship-in-a-bottle exercise. Spot, drill undersize, flatten a circular region around the hole (with a bolt, nut, and washers?), drill final size to get it round, clean up edges so you don't rip the bulkhead fitting seal, flatten again... ugh. Then get the fitting into your hole from the inside, and need a wrench to hold the inside nut, which fits thru the bottle's narrow opening... PITA $\endgroup$
    – Pete W
    Feb 18 at 0:27
  • $\begingroup$ Isn't that a thermos bottle? With double walls and a vacuum in between? Or do you not care about preserving that? $\endgroup$
    – DKNguyen
    Feb 18 at 0:39
  • $\begingroup$ @DKNguyen single wall on the container. Double wall on the cap. $\endgroup$ Feb 18 at 0:46
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    $\begingroup$ @PeteW The top is double walled, there is an exterior piece of copper (which you can see in the picture), and there is an interior piece of copper which touches the liquid inside. I would have to drill through both pieces of copper. But I believe if I did the threads would not sufficient outward pressure to hold their form when I was closing the bottle. It seems like they did that for a reason. Have the copper at the top and bottom of the threads probably makes it rigid enough to have a copper top. $\endgroup$ Feb 18 at 0:48
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    $\begingroup$ @PeteW I think doing it manually with the right tools will obviate the need for back support. See my answer. $\endgroup$
    – DKNguyen
    Feb 18 at 14:41

3 Answers 3

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I would get fittings and solder - plumbing solder is now lead-free at least where I am. It does not flow quite as well so you must use a flux.

Make sure any coating is removed where you are soldering and clean the fittings as well - scotchbright works well.

Given how copper transfers heat you will probably need a torch and heat the fitting first then gently bring in the copper, otherwise you could overheat the thin copper.

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    $\begingroup$ I might then build up support with epoxy. My experience soldering intersecting thin components (as opposed to overlapping) has not been good, structurally speaking. $\endgroup$
    – isherwood
    Feb 18 at 14:16
  • $\begingroup$ @isherwood Small 1"x1"x1/8" (or maybe 3/16") copper plate sanded against sand paper glued to the bottle to form a contour? Then drill it. The thickness lets it have overlap with the fitting and area gives it overlap with the bottle. $\endgroup$
    – DKNguyen
    Feb 18 at 14:52
  • $\begingroup$ You could fill the bottle with ball bearings too. That might help increase the margin for error with the overheating. $\endgroup$
    – DKNguyen
    Feb 18 at 15:02
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Drilling thin material under power is already dangerous. The spiral flutes catches the material and pull. Drilling radially into a curve also requires stability and accuracy or you will skate. You have no chance with an unsupported a power hand drill in either case. Even with a drill press it will be tricky.

The step drill, like a regular drill also has a web which requires high pressure. Step drills are designed for sheet material which is why no spiral flutes to pull, but your step drill has a 135 degree web which is even larger than the typical 118 degrees. Not conducive to low pressure. It will collapse the thin wall. It's meant to be used with back support.

Instead, start the hole by hand with a V-engraving bit in a pin vise. These are very pointy and sharp so minimal pressure required and will immediately anchor itself into the material to prevent skating. Also it's by hand so you can gauge when it is 90 degrees and digs in without it going out of control if it is off. The point of a spade bit will probably work too.

Then the hole gives nothing for the web of subsequent drills to press against so only the flutes cut which should reduce the drilling pressure. Then manually work your way up in size with drills.

Once the hole gets big enough to fit a tapered hand reamer, use that. These get large diameters and are designed for sheet metal. You probably won't need to support the back of the material if you do it this way.

Remember to deburr the hole on the inside face. You'll need deburring tool or something resembling it which looks like a hook-shaped knife thing to get at it.

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I would caution against solder, generally I recommend going with something food-grade. I can be over-cautious about that sometimes but I would hate to be responsible for making someone sick.

My recommendation would be to flatten a portion as best you can before drilling the hole, then apply a food-grade seal such as this O-ring to make up for any remaining curvature in the surface.

Alternatively, you could drill a smaller hole, flatten the surface as best you can, then re-drill the hole to ensure the proper hole dimensions. I hope that helps!

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