So here's the deal - I'm stumped. My 2002 Winnebago with an Atwood 10 gallon water heater just lost all hot water pressure overnight. Cold water works perfectly fine, but turn that handle to hot and... nothing. Zero pressure at any faucet.
The weird thing is the tank itself has hot water and pressure - I can open the relief valve and water shoots out fine with good pressure. It's like something is blocking the hot water from getting out of the tank to the faucets. I've checked what I can reach and don't see any obvious blockages in the lines.
Anyone know what could cause hot water pressure to just disappear like this while cold water works normally? There's gotta be something simple I'm missing here.
No hot water pressure with working cold is usually stuck backflow preventer in hot water outlet. Located near tank connection behind water heater. Tapping the device or manipulating the spring frees the stuck valve.
Excellent troubleshooting work! You correctly identified that a stuck backflow preventer on the hot water outlet was causing your 2002 Winnebago Adventurer's hot water pressure loss. The fact that you had hot water in the tank with good pressure at the relief valve, but zero pressure at faucets, combined with cold water working normally, pointed directly to an obstruction in the hot water distribution system. Your methodical approach of checking the bypass valve, flushing the tank, and testing line continuity was spot-on. The simple tap to free the stuck spring in the backflow preventer solved the issue - this is a common problem with Atwood 10-gallon systems, especially after recent pump work that can stir up sediment.
Hot water pressure loss with no cold water issues typically stems from problems in the hot water distribution system. The most frequent culprit is a stuck backflow preventer (technically a check valve - RVers often use the terms interchangeably) on the hot water outlet, which is exactly what you experienced. These devices use a spring-loaded check valve that can get debris lodged against the seat, completely blocking flow while still allowing pressure to build in the tank.
Other common causes include sediment buildup at the tank outlet, kinked or collapsed hot water lines, and rarely, a failed dip tube inside the water heater. In your Atwood system, the backflow preventer is located right at the tank outlet and serves to prevent hot water from flowing back into the cold water supply during thermal expansion. When these get stuck closed, you get exactly the symptoms you described - hot water in the tank but no flow to fixtures.
The timing after your pump replacement isn't coincidental. New pumps often create different pressure pulses and flow patterns that can dislodge sediment or debris that's been sitting in the system, causing it to migrate to restriction points like backflow preventers.
For this type of repair, you'll need basic hand tools including adjustable wrenches, channel lock pliers, and possibly a socket set depending on your specific fittings. Have towels ready as you'll be working with pressurized water lines. Turn off the water heater (both 12V power and propane/electric heating elements) and let it cool if it's been running - you don't want to work with scalding water.
Shut off the water pump and relieve system pressure by opening faucets. You'll also want to have the water heater bypass valve easily accessible since you may need to isolate the heater during testing. If possible, have a flashlight or headlamp since these backflow preventers are often in tight spaces behind the water heater.
Consider having a replacement backflow preventer on hand (consult your specific Atwood model documentation for correct part numbers as 10-gallon models have different outlet configurations, typically around $15-25) in case the existing one is damaged beyond a simple cleaning. Also have pipe thread sealant or Teflon tape ready for reassembly.
Start by confirming the problem location using your bypass valve test - if hot water flows normally in bypass mode but not in regular mode, the issue is definitely at the water heater outlet. Access the back of the water heater, which often requires removing panels or working in tight spaces as you discovered.
Locate the backflow preventer on the hot water outlet line - it's typically a small cylindrical device threaded directly onto the tank outlet or inline in the hot water supply line. Before disconnecting anything, mark the orientation and take photos for reassembly reference. Ensure system pressure is fully relieved - any residual pressure in the isolated hot water system could cause dangerous spray when fittings are loosened.
Carefully disconnect the hot water line from the backflow preventer using appropriate wrenches. Be prepared for water spillage and potential scalding from residual hot water in the lines even after cooling. Once disconnected, you should be able to feel or see the spring mechanism inside. Try the gentle tapping method you used - often this dislodges debris without full disassembly.
If tapping doesn't work, you can remove the backflow preventer entirely for cleaning. Disassemble it carefully, noting the order of internal components. Clean all parts with water, checking the spring and seat for damage. Reassemble with pipe sealant, reconnect the supply line, and test the system thoroughly before putting everything back together.
While you successfully resolved this issue yourself, there are situations where professional help is advisable. If the backflow preventer is damaged and needs replacement but you're uncomfortable with the plumbing connections, especially in the tight spaces typical behind RV water heaters, a mobile RV technician can handle this efficiently.
Call for professional assistance if you discover the problem isn't actually the backflow preventer - for instance, if you find collapsed or damaged hot water lines that require routing through walls or cabinets. Also, if your troubleshooting reveals issues with the water heater tank itself, such as internal failures or significant corrosion at outlet fittings, this typically requires more extensive repair or replacement.
Additionally, if this problem recurs frequently, it may indicate broader water quality issues or problems with your new water pump creating excessive pressure fluctuations. A professional can evaluate the entire system and recommend filtration or pressure regulation solutions to prevent future occurrences.
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