The transfer pump lines are 5/16" OD. I believe I used 1/4" ID tubing to re-plumb the Rieger, with no issues (it's a tight fit, but that is a good thing). The lines between the reservoir and main pump are a larger diameter. HTH Al > Just wondering if someone knew, off the top of their head, > what the diameter( ID) is of the transfer pump's output hose. > > Thanks, > John