I use a thermostatic mixer from Grohe (though there are more manufacturers in the recent years, including IKEA), and it handles normally both heating/cooling of

I use a thermostatic mixer from Grohe (though there are more manufacturers in the recent years, including IKEA), and it handles normally both heating/cooling of the valve itself, and fluctuations of pressure in the pipes (when someone flushes the toilet). Our hot water supply is off for 2 week per year for maintenance, and I use heater tank (which stores 30 L of hot water, enough to take a generous shower for 1 person). This way, cold water pressurizes both the cold valve, and the tank and the hot valve. I expected some random oscillations, but no, the thermostatic mixer worked just fine. This is the one I have: https://external-content.duckduckgo.com/iu/?u=https%3A%2F%2Fassets-large.qssupplies.co.uk%2FL-2016-6-3--12-5-5-604.jpg&f=1&nofb=1&ipt=456c5e5f2dcb3416b7c9c9c63797adbed292014cb97820784f384c99484fec9c&ipo=images https://external-content.duckduckgo.com/iu/?u=https%3A%2F%2F...