Caleffi’s 521 MixCal, 5213 and 5231 series adjustable thermostatic mixing valves are used in residential and commercial systems producing domestic hot water or in hydronic and radiant heating systems. Compensating for both temperature and pressure fluctuations of incoming hot and cold water in point-of-distribution or point-of-use (scald protection) applications, these low-lead-certified valves maintain the desired output temperature of the mixed water. Check valves in inlet hot and cold ports are optional for the 521 and 5231 and standard for the 5213. The 521 and 5231 are certified to ASSE 1017, while the 5213 is certified to ASSE 1070.