Problem with Grohe thermostatic valve

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Morris

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I have Grohe rough-in 34 397 installed and I'm having trouble with the temperature calibration. The service stops are horizontal (open) and the hot water tank is producing plenty of hot water (as checked in the sink), but I can't get the water temperature in the tub above 75 degrees even with the adaptor turned all the way to the left. I closed and opened both service stops to insure that hot and cold are both flowing, but hot is just luke warm. Any suggestions?
As a side note of information, I'm extremely frustrated with Grohe's instructions right now - when purchasing trim 19615, I was told to use Rough-in 34397, but the instructions packaged with the trim are for 2 completely different rough-ins. I couldn't make sense of why I was missing parts until I realized it was a different rough-in. The trim instructions from their website, however, are for my rough-in and those are the instructions I'm now following. Very aggravating.
 

WorthFlorida

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Two things to try but I think you may already have performed this.

1) Turn off the cold water stop and just run the hot water. There should be the expected water flow and be hot. If the water pressure is very low it probably is the cartridge.

2) Turn off the both hot and cold stops. Remove the cartridge and check for any debris. Open the hot water stop to flush out the valve body. Let it run until it is as hot as expected from your water heater. Then reinserted the cartridge and check. If still luke warm it’s the cartridge.

Is the cartridge the same for both rough-ins? Thermostatic cartridges usually have moving parts to prevent scalding and they sometimes get jammed. Tapping it a few times may loosen it up. At one time moen cartridge had this issue until they made a change.
 
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SWong

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Morris,
If by chance you still haven't resolved your issue do what I did recently and just upload a copy of your invoice and a picture of your problematic part to Grohe's website. After almost 3 years of faithful service on my Grohe shower valve it started dripping so I emailed Grohe requesting a replacement thermostatic cartridge after providing documentation of my ownership. They fedex'd me a replacement thermostatic valve "gratis". Total install time $15 minutes and things are like new. Grohe fixtures are NOT cheap but heir warranties and guarantees are amazing. My roughin box is a 35-026 which is slighly newer than yours which is why I went with Grohe. Fantastic design, German quality, and extremely easy to service and repair
 

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RicksHouse

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Morris,
If by chance you still haven't resolved your issue do what I did recently and just upload a copy of your invoice and a picture of your problematic part to Grohe's website. After almost 3 years of faithful service on my Grohe shower valve it started dripping so I emailed Grohe requesting a replacement thermostatic cartridge after providing documentation of my ownership. They fedex'd me a replacement thermostatic valve "gratis". Total install time $15 minutes and things are like new. Grohe fixtures are NOT cheap but heir warranties and guarantees are amazing. My roughin box is a 35-026 which is slighly newer than yours which is why I went with Grohe. Fantastic design, German quality, and extremely easy to service and repair

Hmm, I was planning to use Grohe shower valve in my new bathroom (my plumber really likes them), but leaking within 3 years makes me question their reliability. Have others noted reliability issues with Grohe?


As an aside, I've been a long time lurker on this site and have really learned a lot from you all. I originally landed on this site when replacing a toilet myself, which is about as far as my skill in plumbing goes. But even though I typically call my plumber for most jobs, it's nice to know the background behind things.
 
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Jadnashua

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I have a Grohe thermostatically controlled tub/shower valve that was installed in 2005. The aquadimmer (volume control) started to leak after about 14-years. The thermostatic control still works fine. They consider something that old, worn, and the warranty is for defects, not wear, so I had to buy it. Some of the other manufacturers will send you out a new one 'free'. My Grohe faucets have been fine. One of them did leak fairly shortly after install, but they sent me a new cartridge for it for free, and it was easy to install...been fine since. The Grohe stuff seems to be pretty robust - they have more in metal than many of the others out there and their plating seems top notch.

I remodeled my Mother's bathrooms for her, and she liked Delta. The new tub/shower valve leaked immediately, they sent me a new cartridge for it, so none of them are immune.
 
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