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While installing a reverse osmosis water filter system, I noticed that the distributor correctly sent the homeowner an airgap faucet, but instead of sending a saddle drain with a 3/8" connection and 3/8" OD tubing to match the waste water drain outlet on the airgap faucet, they sent a saddle drain with a 1/4" connection and 1/4" OD tubing. Not good.
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With the pieces of the 1/4" connection removed, the opening could be tapped to accept the male threads of the new 3/8" connection.

Next, I had to make the tap using a 1/4" galvanized pipe plug and an angle grinder.
This next picture shows a little more clearly the problem....
Note the crack around the arbor hole.
Unfortunately, going to a specialty store or waiting for the distributor to overnight a 3/8" saddle drain were not options, since it was 5 o'clock, and this system had to be working that night. I had to make it happen with what I had, which meant modifying the 1/4" saddle drain they provided.

First, I would take apart the saddle drain by removing the 1/4" connection. It was actually 3 pieces....
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Always inspect your tools and equipment before you use them! Had this cutoff wheel come apart during high RPM usage, I may have sustained serious injury.
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After changing cutoff wheels, I was able to put a kerf perpendicular to the threads, then remove a little more metal...
...forming a perfect cutting edge...
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...to tap the plastic of the saddle drain.
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What a beautiful new set of threads!
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Next, apply pipe dope to the mating surface...
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...and screw the quick-connect fitting into the saddle drain.
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No leaks....Mission accomplished!
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