I don't think anyone was suggesting 3450 RPM but even if you did, it would not blow out your pipes. 1.5" schedule 40 is rated to 200 PSI.

I have found a happy medium of 1350, but am not sure if this is enough.
Enough for what?


If your vacuum works at the speed, then use that. If not, then increase the speed until it starts to work. If it works at a lower speed that use that. There is no one perfect speed for everything, just use trial and error.

My main point was that efficiency wise, you want to get as close to 1000 RPM as possible but lower than that, the pump becomes less efficient.