Found the part in the picture frozen open when we opened our cabin. The metal strap was my attempt at a temporary repair so we had water for the weekend. We can't figure out what this is used for. It had an adjustable piston like thing and springs on the inside. It has a cold and hot water feed and one output. We put it back without the guts and everything in the house appears to be working normally, except the two toilets now fill with warm water. Anyone know what the purpose of it is, and where I might be able to find a replacement? Thanks for your help.