there is a shower valve that slowly closes as the hot water in the shower gets hotter so that there is no wasted hot water.
I forgot the name of it and where to buy it.
can anyone help please
Unless the shower valve you refer to is entirely new, there are basically 2 types of shower valves in use by most manufacturers today. They are Pressure Balanced Valves and Thermostatic Valves. Below is a link which explains how each works.
From the sounds of your description of the valve, you may find that it is the Pressured Balanced Shower Valve that you are referring to as it does respond to changes in water pressure by maintaining the previously set water temperature should the water pressure change by sudden water usage elsewhere in a home thus preventing dangerous scalding hot and unpleasant cold water surges while in the shower.
Others may have additional suggestions.
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