> The most common solution is probably a double throw valve. Bulent Alieve has
> a source of fairly inexpensive ones. I installed a solenoid which sends the
> return to the right tank when off, left when energized. I energize it with
> the left tank fuel pump switch. This way I have independant fuel supplies,
> pumps and filters. The solenoid weighs a couple of pounds. See details &
> pictures in http://kgarden.com/cozy/chap21b.htm search for hydraulics.

John, I really like your system, especially the isolation it provides and the ability to transfer fuel from one tank to another by controlling where the return goes. I have one question. When your solenoid fails it's just in one position or the other, so the return still has a place to go and you can just draw from that tank only to keep the plane balanced. But how do you know this has occurred? Have you had any thoughts regarding that, or is it just going to be a "plane's leaning, sir" seat of the pants feeling, and take a guess that the solenoid might have failed?

It's not a disastrous failure of course, but I've been trying to figure out a way to detect this without two more flow rate sensors on those returns and can't come up with much. I thought that perhaps a short section of clear tube, a small ball, and something for it to catch against could be used as a sight tube, if you don't mind running the return plumbing somewhere it can be seen - if the fuel is flowing, the ball (sized so fuel can flow around it easily, of course) will be fetched up against the screen/stop/etc.

But it's an additional complexity. Have you experimented with your valve at all, electronically? Might it possibly react to, say, a blockage, in some recognizable way, like excessive current consumption?

Regards,
Chad