Rare Grohe shower valve teardown in Sandy

We got called out to Sandy, UT for an older Grohe shower valve. It’s a German design, very high-end, but not so common in Utah. This was the first one I’ve ever encountered, and looking online for more information led to not many results, so it felt important to document how this valve works and comes apart.

What made it interesting is that this valve does not operate like most. It has the temperature controller before the shower shut-off valve. We initially believed it to be the thermostatic cartridge contributing to the problem. Once we got into it, another issue showed up: the little plastic plunger that controls the temperature when you turn the valve on and off was broken.

We later identified that was due to extremely high pressure at the house. The pressure reducing valve had failed, leading that piece to break. For anyone curious how it comes off, that piece just spins right off the shaft. We weren’t able to complete the repair this time, but that’s OK. We will be back to change the pressure valve and finish this at a later date.