So I'm winterizing my 2022 Tiffin Open Road 34PA and running into this annoying issue where my water pump keeps losing prime. I can get it back by quickly opening and closing one of the lowest drain valves, but then it just loses prime again after a while. This has happened on other RVs I've winterized too, but it's particularly stubborn on this Tiffin.
I'm suspecting it might be the inline check valve next to the pump or maybe the one behind the Truma hot water heater, but I'd love some guidance on proper diagnosis. What are the most common causes of prime loss during winterization, and what's the best way to troubleshoot and fix this? I want to make sure I'm covering all my bases for winter storage prep.
Water pump prime loss during winterization is commonly caused by faulty check valves, air leaks in suction lines, or worn pump components. This comprehensive guide covers diagnosis, repair procedures, and preventive maintenance for RV water systems.
Your 2022 Tiffin Open Road 34PA is losing prime because you likely have an air leak somewhere in the system, most commonly in the pump inlet line or that check valve you mentioned. The fact that opening and closing a low drain valve temporarily restores prime tells us the pump can create suction, but air is getting into the system upstream of the pump. Since you've winterized 7 different RVs and this is behaving differently, there's definitely something specific to your Tiffin's plumbing configuration causing this issue. The inline check valve you ordered is a smart move - that's often the culprit on these newer Tiffin units.
The intermittent nature of the problem suggests the leak isn't massive, but it's enough to gradually allow air into the system when the pump isn't running. Good news is you completed the winterization with antifreeze, so your system is protected. Now we just need to track down this annoying air leak so next season runs smoothly.
Prime loss in RV water systems typically occurs when air enters the plumbing somewhere between the fresh water tank and the pump. In your 2022 Tiffin, there are several common failure points. The inline check valve on the pump inlet side is notorious for developing internal leaks - the internal mechanism deteriorates or gets debris stuck in it, allowing air to backflow into the line when the pump stops.
Another common issue on Tiffin units is the connection fittings on the pump inlet line. These push-to-connect fittings can develop micro-leaks over time, especially with the vibration from road travel.
The check valve behind your Truma water heater is usually less problematic for prime loss since it's downstream of the pump, but it can cause circulation issues. Your symptom pattern - losing prime gradually then regaining it when you manipulate a drain valve - strongly points to the pump inlet side check valve or connections.
Start by installing that new inline check valve you ordered. First, shut off power to the water pump and depressurize the system by opening a faucet. It's typically located on the inlet side of your water pump, usually in a clear or white housing that may unscrew by hand or require pliers/wrench depending on your model. Before removing the old one, take a photo of the orientation - check valves only work one way. Drain any residual water/antifreeze from that section, then unscrew the housing and replace the internal check valve mechanism.
While you have the check valve housing apart, inspect the O-rings and replace them if they look worn or dried out. Apply a thin coat of silicone grease to the new O-rings before reassembly. Thread the housing back together hand-tight plus a quarter turn with pliers - don't over-tighten as you can crack the plastic housing.
If the new check valve doesn't solve the problem, systematically check every connection on the pump inlet line. Start at the fresh water tank pickup tube and work your way to the pump. After temporarily adding water to pressurize the system, spray soapy water on each fitting - you're looking for tiny bubbles that indicate air leaks. Pay special attention to any push-to-connect fittings, as these are common failure points.
When ready to test your repair in spring, first flush all antifreeze from the system by filling the fresh water tank and running water at all faucets until clear water flows. Then refill with fresh water before testing - fill the fresh water tank with a few gallons of water, turning on the pump, and running water at a faucet until you get steady flow. Then turn off the pump and wait 10-15 minutes. If the pump doesn't cycle on its own when you open a faucet, you've likely solved the prime loss issue. If it still loses prime, you'll need to continue checking connections further downstream or consider that the pump itself might have internal seal issues.
This repair is well within most RV owners' capabilities, especially since you've successfully winterized multiple RVs. The check valve replacement is straightforward, and connection leak hunting just requires patience and methodical troubleshooting. However, if you discover the problem is internal pump seals or complex plumbing modifications related to your washer/dryer removal, that might warrant professional attention.
Don't hesitate to call a Tiffin service center if you find evidence of factory plumbing modifications or if the problem persists after replacing the check valve and inspecting all visible connections. Sometimes these units have routing quirks that aren't obvious from service manuals. Given that your RV is only two years old, there might even be warranty considerations if this is a known issue with your specific model year.
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