Have you guys thought about using All-Flo Air Diaphragm pumps instead of the 12V's?
One 3/8" All-Flo KE-038-B3 pump will last 50 million cycles!!!!!!! (All wetted parts have a "A" Chemical Rating) We consider these pumps as the best pumps out there...
It may seem a bit expensive on the start-up because you need to buy a compressor. However, you will never have to babysit the pump again and you won't have to religiously rinse out the All-Flo after each use. We have dealt with All-Flo for many years now.
We offer the full line of All-Flo Pumps at Pressure Washer Products.