RV Toilet Won't Hold Water: Fix Bowl Drainage & Sewer Smells

Tools & Parts Needed

Find these on Amazon: Dometic Toilet Ball Seal Kit , RV Toilet Seal Lubricant , Thetford Toilet Blade Seal

The Quick Fix

When your RV toilet won't hold water in the bowl and you're experiencing sewer smells, the problem is almost always a faulty seal at the bottom of the toilet.

Your Toolkit

• Rubber gloves
• Toilet paper or rags
• Flashlight or headlamp
• Bowl cleaner or mild soap
• Replacement seal kit (if needed)
• Screwdriver set
• Pliers (possibly)
• RV toilet seal lubricant

How to Fix It

1. Turn off water supply to the toilet and flush to empty the bowl completely. Safety first: Turn off electricity to any electrical toilet components before beginning work. Ensure adequate ventilation when working with sewer connections.
2. Inspect the toilet type: Dometic toilets typically have either a ball seal (round mechanism) or blade seal (flat mechanism) at the bottom of the bowl.
3. Check for visible debris: Look into the bowl opening for toilet paper, waste, or mineral buildup around the seal area.
4. Clean the seal area: Remove any visible debris carefully with gloves. Use a toilet brush or rag to clean around the seal thoroughly.
5. Test the seal mechanism: Press the foot pedal or flush handle to open and close the valve several times. Listen for proper operation and watch for smooth movement.
6. Inspect the seal itself: If cleaning doesn't work, remove the toilet from the floor (typically 2-4 bolts) to access the seal assembly underneath.
7. Replace the seal if damaged: Remove the old seal assembly, clean the mounting area, and install the new seal with a thin layer of RV toilet seal lubricant for proper sealing.
8. Reassemble and test: Reinstall the toilet, turn water back on, fill the bowl, and monitor for several hours to ensure the fix worked.

Understanding the Issue

The ball seal, blade seal, or valve mechanism isn't creating a proper seal, allowing water to drain and sewer gases to escape. This is typically fixed by cleaning debris from the seal area or replacing the seal assembly.

Debris buildup: Toilet paper, waste particles, or mineral deposits prevent the seal from closing completely. This is the most common cause and often the easiest fix.

Warped or cracked seals: Over time, rubber seals deteriorate from chemicals, heat, and normal wear. A warped ball seal or cracked blade seal won't maintain a water barrier.

Misaligned components: If the toilet has been removed for repairs or the RV has experienced significant bouncing, the seal assembly may be misaligned.

Worn valve mechanism: The spring-loaded mechanism that operates the seal may weaken over time, preventing full closure.

Leave These to the Experts

Contact an RV service technician if you discover cracked toilet flanges, damaged floor around the toilet base, or if the black water tank itself appears to be leaking. Also call a professional if you're uncomfortable removing the toilet from the floor or if multiple attempts at seal replacement haven't resolved the issue.

Long-Term Care

Use RV-specific toilet paper that dissolves quickly to prevent debris buildup. Add a small amount of water to the bowl after each use to keep seals moist. Avoid harsh chemical cleaners that can damage rubber components. Inspect and clean the seal area monthly during heavy use periods. Consider using RV toilet seal conditioner quarterly to extend seal life.