Arbor Biofuels now has a really cool dry wash metering pump available that'll fit towers with pumping needs up to 9 GPH.

I just created a page for it with all the specifics including pumping capacities, size, and pictures of what it looks like.

It runs $433.50 and is made of 100% Biodiesel Compatible materials and will work extremely well.
It's also adjustable so that you can flow from almost 0 clear up to 9.9 Gallons Per Hour.

Here's a picture of what it looks like:


It'll deliver a consistent flow up to the rated 9.9 GPH and won't ever exceed 30 psi.

More details on this cool, new pump are here:
http://www.utahbiodieselsupply.com/drywashpumps.php

-Graydon