As for the "Stress Coat" type stuff, I can vouch for that causing problems. Stick with Prime and you won't have that particular problem. I used it once in a pinch when I did not have Prime and it sent my skimmer into orbit. Following along with what CXF2 said, I have 2 ERs and they are just terrific. One is like yours with the downspout job and the other is a recirc model. As much as I love the RS250, man those recircs are really darn hard to be. For the money though, I don't think you can beat ERs in general.