This is an updated version of the product training course introduced by SUPPLY HOUSE TIMES in 1979, authored by Don Arnold.
The subject of shower valves has been somewhat simplified in recent years, due to code regulations that require protection against sudden temperature fluctuations. This has eliminated much of the plain single-lever, two-handle valve business that once dominated this field. (That is not to say that we no longer see single-lever and two-handle shower valves - but those that are sold today are usually equipped with this additional protective capability.) Why the need for such protection? Just recall the last time you took a shower without it, and someone flushed a toilet nearby. There are two basic technologies used in maintaining consistent temperature output - thermostatic and pressure balance. As a basic distinction between the two, here's what you need to understand:
1. Thermostatic valves provide this protection by sensing and responding to variations in actual output temperature - whatever the cause.