My TC doesn't have a holding tank either. Had a black water one, but I took the shower out and use it for storage. The single kit sink drains directly out the side, then into a cut section of garden hose and into a water container. Water tank isn't that big.My rig has no holding tanks! I use a pickle barrel sitting outside the rig as a kind of cistern for My plumbing system.
My bumperpull though is bigger and has both tanks--which is the one I replaced in. Come to think of it, I replaced them in both RVs. Mebbe I'm the weird one.