Thermostatic valve

[Alexander Galkin]

Does anyone have experience with thermostatic shower valve, particular Grohe valve? I am trying to calibrate it but no luck. It either produces very hot or very cold water, no in between. I am trying to figure out if the valve does not work or I am doing something wrong.

[Yasashii Arbaito]

Calibration *should* be easy; instructions are at

However, it sounds like there's something wrong with yours - you should have a nice smooth transition from cold to hot. Some things to check:

1. Are both cold and hot water pipes and inlets clear of all debris?
2. Are cold and hot water pressures more or less the same (no kinked pipes on one side or the other, or unusual drains on one side)?
3. Are both stops fully open?
4. Are the cold and hot water supplies connected to the correct sides?
5. Is the hot water supply at least 15 degrees F above the desired temperature?

Beyond these, it's possible the thermostatic valve itself is obstructed or defective. However, I'd give Grohe a call before trying to take it apart. We did get a defective Grohe volume control valve once, and once we were able to convince them of that, they rushed out a replacement to us.

[Alexander Galkin]

I followed these instructions but I still have strange results. Water is either very hot or very cold regardless if I set handle to 100 degrees or 70 degrees. I am trying to figure out if the valve does not work I am doing anything wrong. I have inverse hot and cold water connections to the valve. Is there way to check if the valve works. The instructions say that connection to the valve should not be soldered. So I use thread adapter that I screwed into the valve. But the opposite side of the adapter I soldered to the pipe. Of cause the valve body became hot when I soldered thread adapter to the pipe. Can this damage the valve. However, I can't imagine other way to attach a pipe to the valve. Any help and/or advise would be greatly appreciated.

[Yasashii Arbaito]

Are you saying you've reversed the hot and cold inlets? You don't want to do that!

Well, I know with some thermostatic cartridges, you can put them in hot (>120 degree F) water and see if they "pop" but I don't know if the Grohe does anything visible (haven't had any problems with ours).

I imagine you already know the answer here - it's a paraffin cartridge, and it (and other parts) can certainly be damaged by excessive heat. I'd guess it'd probably be ok up to around 180 degrees F, but any higher is certainly a risk. And at the price of those cartridges (around $130), it's not a risk I'd care to take.

Here are five different ways of handling it:

1. Wrap a damp rag around the body of the valve when soldering; should keep it cool enough if you're quick with the torch.
2. Remove the cartridge and any other sensitive parts before soldering.
3. Use compression unions to connect to the water supply.
4. Use stainless mesh flexible supply connectors to make the hookups. I've only personally seen these in 1/2" and smaller, but they're probably made in 3/4" also.
5. (What I did) Solder long "legs" on the threaded adapters before screwing them in to the valve. I used right-angle bends and soldered on approximately

3 foot lengths of pipe. When I attached these to the water supply, the connections were so far from the valve that heat wasn't an issue. (I still wrapped the rag around the valve for paranoia's sake.)

[Alexander Galkin]

first of all the Grohe thermostatic valve that I have does allow reverse hot and cold water installation. The manual clearly states this. It is not clear for me however, what has to be turned 180 degrees for that.

What do you mean "pop" in very hot water? I still need some reliable way to check if the valve is OK or not. The problem with soldering is that volume valves can be disassembled before soldering, but thermostatic - not. At least manual does not say anything about it, just not to solder pipes to valves. I would really love to disassembling the valve to make sure it is not damaged.

approximately

[Yasashii Arbaito]

Ah, sounds like it would be good to figure that out.... The Grohe web site has diagrams for all their valves - go to

enter your part number, and check it out.

I just did that, and found for mine at least (an older model) they list a normal and reverse thermostatic cartridge, which sure makes it sound like it's a separate part to reverse hot and cold. (Or perhaps it's just to make it turn the other way.) In our case, we moved the controls to the opposite wall in redoing the shower, but flipped the pipes to make up for it.

Some thermostatic cartridges actually have a little piston that pops out above a certain temperature, sort of like a turkey pop-up timer. But I don't know if the Grohe ones are like that.

Check the Grohe site - the exploded diagrams also indicate what's needed to take things apart. And I've already mentioned a bunch of ways to do the soldering safely.

[mark Ransley]

Is it possible some grit got stuck in the valve base or valve, take it apart and examine carefully for debris

[John Gilmer]

We put in a valve than senses the hot and cold water pressures but doesn't care about the temperature. This works just fine: flush the toilet and the shower valve maintains the same mix.

For most purposes, this is BETTER than a slow acting thermostat type valve.

[Yasashii Arbaito]

I think you're confusing shower thermostatic valves with those intended for other purposes. Shower valves that meet ASSE 1016 are *fast* acting, at least in terms of human temperature perceptions.

Pressure-balancing valves are fine in their place, but don't have the flow capacity to handle a multiple outlet setup like the original poster had.