It’s Doing What? RV Holding Tank Issues.

Welcome to another edition of Todd’s Two-Minute Tech Tip Tuesday, proudly brought to you by the National RV Training Academy, the largest hands-on RV training academy in America.

Today, we’re tackling a pressing question from one of our viewers regarding a plumbing issue in their RV. Unfortunately, the email didn’t include the sender’s name, so let’s respect their privacy and dive straight into the problem.

The Problem: Water Shooting Out of the Bathroom Sink

The viewer reports that when they close their gray tank designated for the shower and washer, and proceed to run the shower, water starts shooting up through the bathroom sink drain. They’ve already ruled out a faulty air admittance valve as the cause of this issue.

Todd’s Analysis and Solutions

1. Misidentified Tank: One potential issue Todd suggests is that there might be a misidentification of the gray tanks. It’s possible that the tank labeled for the shower and washer isn’t the one being filled up when the water is running. Sometimes, RVs may have mislabeled valves, leading to confusion about which tank is actually in use.
2. Vent Stack Blockage: Another likely culprit is a blockage in the vent stack. The vent stack allows air to enter the plumbing system, preventing airlock issues and facilitating proper drainage. If this vent stack is clogged—perhaps by debris like a bird’s nest or wasp nest—the trapped air has nowhere to escape, causing water to back up through the sink drain when another drain is in use.

Steps to Resolve the Issue

• Check Tank Labels: Verify if there are indeed two gray tanks and ensure they are correctly labeled. This involves opening and inspecting each tank to see which one corresponds to the shower and washer drainage.
• Inspect the Vent Stack: Climb up to the roof of your RV and inspect the vent stack. Look for any signs of blockage, such as debris or obstructions. Use a water hose or a flexible rod (like half-inch PEX tubing) to clear out any debris stuck in the vent stack. Ensure that the vent stack is clear all the way down to the tank.
• Test for Vent Stack Functionality: After clearing any potential blockages, open the gray tank valve and listen for the sound of glugging as water flows out. This confirms that the vent stack is functioning correctly, allowing air to enter as water drains out.

Conclusion

Resolving plumbing issues in an RV often requires a systematic approach to identify and address the underlying cause. Whether it’s clarifying tank labels or clearing vent stack blockages, these steps can help restore proper drainage and prevent water backup issues in your RV’s plumbing system.

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