> If we're talking about elegance here, I'd almost rather see
> something in "Y" form where the valve is a butterfly between two
> inlets and combines the flows into a single outlet. Then only one
> valve is needed. If only one pump is pushing, the butterfly valve
> would block reverse flow into the other pump. If both pumps are
> pushing the butterfly valve would open relatively evenly
> (assuming equal flow from both pumps) and allow both to flow.
>

Last week before I flew with the existing single pump arrangement, I built
exactly what you're talking about here. It is a "T" that combines the flows
with a flapper valve. It took about 2 hours to weld it up from alum and hand
shape it. (last weeks talk of mills and lathes really had me wishing:-).
I've not tested it yet but I had it on hand to install with the replacement
pump if it proved necessary. It weighs 3/4lb. Fortunately it has not been
required so I've opted to keep it simple for now, however extended flight
over water or other inhospitable terrain may make this a desirable feature.
I've just got to be certain that it will not add another failure mode to the
system. I took some pics of it but they are of the olde fashioned film
variety and I've not yet developed them.

S. Todd Bartrim
Turbo 13B RV-9Endurance
C-FSTB
http://www3.telus.net/haywire/RV-9/C-FSTB.htm

   "Whatever you vividly imagine, Ardently desire, Sincerely believe in,
Enthusiastically act upon, Must inevitably come to pass".