I have seen the information below in several locations, but I can not find any further information. I have a brass ball valve on my stainless reactor, and a few brass coupler on my hoses. Is this going to cause a problem, or is it only if you store biodiesel in brass or copper containers? I store my finished product in plastic jugs.

"Brass, bronze, copper, lead, tin, and zinc may accelerate the oxidation process of biodiesel creating fuel insolubles or gels and salts. Lead solders and zinc linings should be avoided, as should copper pipes, brass regulators, and copper fittings."

I dont think it will cause a noticeable problem. I have a modified push/pull reactor with many brass ball valves and a brass flow switch and my bio passes all the homebrewer quality tests without issue.
I think it is more of an issue for storage.
Jon