252158A - Adjustable Thermostatic Solar Mixing Valve with Temp Gauge - 3/4" SweatCaleffi 252158A Adjustable Thermostatic Solar Mixing Valve with Temp Gauge 3 4" Sweat In solar systems, the temperature in the storage tank can vary considerably, depending on the solar radiation, and can reach very high temperatures over long periods. In summer, and if there is little water usage, the hot water at the storage tank outlet can actually reach temperatures around 200 F. At these temperatures, the hot water cannot be used directly because