They make a cassette with a 20' patient line??? I know about the 20' drain line but did not know they had a 20' patient line. I think the ones I use are 10' or maybe 15'.
There is a cassette for the Fresenius Liberty Cycler with a 20ft patient line (your RN may need to add it to your RX). One difference is that the 10ft line has an extra fitting so you can disconnect and reconnect once. The 20ft cassette does not have such a unit, so you have to add the optional multiconnect set if you plan on a disconnect/reconnect. Another difference is that the 10ft cassettes connects to a drain line whereas the 20ft cassette has the drain line integrated as part of the cassette (I think the integrated drain line is also 20 ft, but I'm not certain).
Drain lines can be connected in series, so there isn't really a length problem. The dialysate fill/drain line is limited in length since the flow direction changes and there is a limit as to how much can be left in the tubing when changing directions.