You likely sussed out the problem thanks to a drip, drip, drip sound coming from the bottom of your RV. “Is that … my freshwater tank?” you wondered. “Why would my tank be full?” Sure enough, the water was leaking out of the tank overflow vent. You double-checked your water connection and bypass valve orientation. Yup, everything was correct. “So …. why is my tank filling up when I’m connected to city water?”

Good question. This is a somewhat common affliction for many full-time RVers. It can have multiple causes. Let’s round up the usual suspects and see which one might be culpable in your case.

P.S. Not all tank overflow tubes exit below the subfloor. Some overflow tubes exit through a sidewall vent. Take note of which one you have!