Temepering valve?

I'm furnishing new darkroom and want tempered water. I've been trying to find something on the net but all I've found are some rather useless house heating stuff or horribly expensive industrial automation parts. Is there a special name for it or can anyone point me to some manufacturers?

I use a Honeywell thermostatic mixing valve to give me a 38C water supply for colour development use; it works perfectly - water temperature is rock solid in my tests. The valve is adjusted to the desired temperature the once and then a cap fitted and screwed down to prevent inadvertent changes later.


I understand that there are legal requirements in certain situations (care homes, that sort of thing) that mandate such a valve is fitted on bathroom water supplies to prevent the vulnerable scalding themselves, and the temperature we require (38C) falls bang in the middle of the acceptable range for these scenarios - so while they're not exactly cheap, they are at least fairly readily available.

I think from memory the valve I use is a Honeywell TM200VP - you can see it on this page towards the bottom:
http://www.onlineplumbingsupplies.co.uk/acatalog/Non_Electric.html

Note that I paid significantly less than that on eBay (for a new, boxed valve.)

Should be easy enough to build a basic mixing valve similar to this (Dead Link Removed) out of off the shelf plumbing parts. That's what I plan to do. Though I will have multiple outlets and a thermometer at the output side of the filter.