Watts mixing valve
Here's a post I saved from a Sailnet discussion list:-----------------------------------------------I posted to this list well over a year ago asking for advice on the problem du jour, which is now solved, I'm happy to report. I don't remember who or when, but someone triggered an important connection - nursing homes.The problem on my boat (402-44) was that after the engine had been running a while, the domestic water coming from the hot water tap was a blistering 185 degrees. I have two small kids -- and that wouldn't do. They open the valve with it set to max hot, and are suddenly filling a quiet anchorage with ear piercing screams.So, someone suggested that I look into something called a 'thermostatic mixing valve' which is used in nursing homes and other places where they are required by local laws to limit the tap water temp to 125 degrees, which, apparently, is a very difficult problem in older buildings.This valve is a hunk of brass and bronze that has three water pipe connections, and a dial. It is meant to be spliced into a hot water pipe -- that's two of the water connections. The third connects to a cold water source. It measures the temp of the hot water, and mixes in an appropriate amount of cold water, and voila! no more 185 degree water at the tap. The dial is simply an adjustment for the desired output temperature, specified as 'warmer' and 'colder', so you engineer types will just have to fiddle with it. It is purely mechanical -- there are no electrical connections needed.It was installed right next to the water heater, and it works almost perfectly. I say almost because when the domestic water pressure pump comes on, the output temp at the faucet suddenly jumps 5 or 10 degrees. I'm not sure why, I would guess that it is because the pressure increase in the hot water line causes a pressure drop in the cold water line because the valve pulls more cold water -- just like opening another spigot would. It takes a couple seconds for it to get back normal, but that is just because the valve isn't quick enough to respond to the change in pressure. But it doesn't jump all the way up to blistering temps. And we are doing our part to reduce the noise in our harbors.Here's the spec sheet on the valve...http://www.wattsreg.com/antiscald/Series_1170.pdf