When I started sourcing parts for mine, I found that Graingers was a good bit more expensive than the same pumps from aquatic sources. Aquatic Ecosystems has Gast and other brand pumps that are known to be oilless and continuous duty; that way you dont have to open up countless spec sheets to see what is what. You can also buy unused pumps from surplus warehouses. They may not have all the latest additions as the newer versions of the same type pump, but are more than adequate. Look at some of the Aeration sites, you will see the best prices for good pumps.
