3D-Printable replacement plastic coupler bit (stem driver) for Kohler Rite-Temp(R) shower faucet handles

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Go for a shower, and the new (professionally installed just over 1 year ago) Kohler shower faucet handle just spins in a full circle with some rough detents without any water coming out. After figuring out what the actual product is and how to extract it from the wall (nary a screw or screw-hiding cover in sight), it’s a Kohler Rite-Temp(R) handle and is actually coupled to the valve in the wall by a small tubular plastic coupler thingy, which ends in a hollow square tube to receive the valve stem. This tube has broken along its corners and basically crumbled apart. Apparently, this is a common problem, with most breaking after between 1-2 years of use. At the time of this writing, the product I have has 9 reviews, 8 of which are 1-star with a wild outlier giving two, all complaining of the failed plastic part with choice words like design flaw, terrible quality, pathetic quality, and stay away.

The broken part is formally known as a stem driver, and it looks like many Kohler faucets have a similar stem driver with minor product-specific geometry tweaks. Now that you know what this plastic part is officially called, you may be able to buy a replacement rather than spring for the whole trim assembly, except that you may be replacing it again in a year1.

It’s a simple bit of plastic, so I just calipered the remains and did up a compatible replacement in OpenSCAD. If you have access to a 3D printer, you can print as many as you like. Snag the design files off Thingiverse or my GitHub.

Printed stem driver with broken original for reference

Dimensions in the STLs and OpenSCAD default values are for the K-TS22028-4-BN / K-TS22028-4-BL / K-TS22028-4-CP / K-TS22028-4-SL. It is likely to work for other Kohler faucet handles by adjusting the length or other geometry values to fit.

When replacing the part, be sure to transfer any hardware, including square gasket and O-ring, from the old part.

The STLs are for the part “as-shipped” (original geometry) and for a modestly lengthened version. On my shower, the original stem driver seemed a bit too short; it had to be blind-mated since it did not engage before the threads on the handle assembly caught, and even when cranked down all the way seemed to barely engage. The lengthened version of the .STL adds 3/8 inches to make assembly easier, especially if the valve stem is recessed into the wall a ways. The mating key of both are slightly oversized (there’s room) for additional strength.

The author of this post and accompanying files is not affiliated with Kohler(R), all trademarks are the property of their respective owners and used nominatively.

  1. Plus, during disassembly, you get to re-enjoy the reminder that the “brushed metal” (e.g.) fixture you just shelled out for is actually just plastic with a thin metallic dip-coating, and you may as well have just 3D-printed the whole thing and given it a hit with hammered-metal spraypaint. ↩︎

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