This won't help Pedro as I believe he is in Europe, but those in Western Canada might find this useful Princess Auto 12V Bilge Pump for $15 (Sorry for the big picture. Can't find a way to post the smaller version.) It doesn't have a temperature rating on it, but I've been using it for months now and it has been working great. It says it runs from 4.5-12V, but I run it all the way down to 1.5V. This reduces pump noise and still gives more than enough water circulation in my slow cooker. It also uses much less current at this voltage so I can use a wall wart to power it. I use a 3/8" piece of hose to get the water from the pump intake at one end of the cooker to the other end. The pump is nice and small, too. Absolutely perfect for SV. By the way, this is my first post after lurking for a few months. As an engineer, I've been impressed by the science and the level of precision I've read in this thread. I hope I can contribute in a small way.
