Symptoms
- Water overflows out of the fill inlet instead of going into the tank
- Tank gauge doesn't rise even after filling for a while
- Filling is very slow
Likely causes
- CommonTank vent blocked or iced overA blocked vent prevents air from escaping the tank as water enters, causing it to back up or fill slowly.
- CommonFill inlet or screen clogged with debrisDirt or mineral buildup at the fill opening can restrict flow.
- PossibleBypass or fill valve in the wrong positionA valve meant to direct water to the tank vs. bypass it may be set incorrectly.
- PossibleFaulty or stuck tank level gaugeThe tank may actually be filling fine, but the gauge itself isn't reading correctly.
What to do
- Check that any water valves near the fresh tank are set to fill the tank, not bypass it (refer to your RV's plumbing diagram if available).
- Locate the tank vent, usually a small pipe on the roof, and check it isn't blocked by debris, a wasp nest, or ice in cold weather.
- Inspect the fill inlet for visible debris or a clogged screen and clean it out.
- Fill slowly and watch the inlet for backing up or overflow, which points to a vent or tank blockage rather than a slow fill rate.
- If the tank seems to be filling (you can hear or see water entering) but the gauge doesn't move, suspect the sensor rather than the tank itself.
- If none of these resolve it, the tank itself may have an internal blockage or a stuck check valve that needs a technician's inspection.
Tools and parts
- Flashlight
When to call a pro
If the tank still won't fill after checking the vent, inlet, and valves, have an RV technician inspect the tank and plumbing.
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.