Fix RV Low Water Pressure on City Connection: Troubleshooting Pump Assembly

What's Going On

When your RV water pump cycles on and off while connected to city water, this indicates a problem with your water system that needs addressing. While you've solved the screen blockage issues, the pump cycling is a separate concern. The fact that your shower has good pressure while the sinks were struggling, combined with your 40 psi reading on the regulator gauge, tells me your main water system is functioning properly - this was definitely a localized blockage issue at those specific fixtures.

Now, regarding your toilet pressure concern and the pump cycling behavior you mentioned, there are a few things happening here. First, let me address the toilet situation: RV toilets typically don't have aerator screens like your sink faucets do, but they can still experience pressure drops due to different factors. The toilet gets its water through a different valve mechanism - usually a ball valve or flapper valve system - and if there's debris in the water lines leading to that valve or if the valve itself is partially obstructed, you'll see reduced flow even without a traditional screen.

The pump cycling you described - running for 5-6 seconds then shutting off - when connected to city water indicates a problem that needs diagnosis. Common causes include a faulty check valve allowing city water to backflow, inadequate city water pressure, loose connections in the city water line, or a malfunctioning pressure switch. Your RV's water pump is designed with a pressure switch that activates when system pressure drops below a certain threshold (usually around 35-45 psi). With city water providing 40 psi, the pump should not run at all if the city water connection is working properly. This cycling pattern suggests your pump and pressure switch are working correctly.

Why This Happens

The screen blockages you discovered are extremely common in RVs because of the nature of how municipal water systems work and how RV plumbing is designed. Unlike residential plumbing that has larger diameter pipes and more consistent flow patterns, RV water systems use smaller diameter flexible hoses and have more fittings, creating opportunities for sediment and debris to collect at restriction points like aerator screens.

Several factors contribute to these blockages:

• Municipal water systems often contain small particles of sediment, rust, or mineral deposits that pass through city treatment but accumulate over time in your RV's system
• Older campground water systems may have deteriorating pipes that shed particles
• The flexible PEX or vinyl hoses used in RV plumbing can create turbulence that causes particles to settle at fixtures
• RV aerator screens are typically coarser mesh than residential ones due to the lower pressure nature of RV systems, making them more prone to clogging
• Calcium and mineral buildup from hard water gradually restricts these screens over time

For your toilet pressure issue, common causes include restriction points in the toilet's water supply system. RV toilets receive water through a supply line that connects to a water valve mechanism inside the toilet base. This valve can become partially obstructed by mineral deposits or debris, or the supply line itself might have accumulated buildup over time. Additionally, some toilet models have small internal passages or jets that can become restricted without any removable screen being present.

The fact that your shower maintains good pressure while other fixtures were restricted actually provides important diagnostic information. This suggests that the main water supply lines are clear and your system pressure is adequate, but individual fixture supply lines or the fixtures themselves were the restriction points. This pattern is very typical when aerator screens are the culprit.

Getting Ready

SAFETY WARNING: Before starting any work on plumbing connections, ensure proper safety precautions. Note that diagnosing pump cycling issues requires city water to be connected to observe the problem. Always depressurize the system completely before disconnecting any fittings.

Before diving into further troubleshooting and repairs, you'll want to gather the right tools and materials. Since you've already addressed the main screen blockages, we're now focusing on the toilet pressure issue and ensuring your entire system is optimized for consistent performance.

For toilet troubleshooting and system maintenance, you'll need:

• Adjustable wrench set (10mm to 19mm sizes are most common for RV plumbing fittings)
• Needle-nose pliers for accessing tight spaces
• Small wire brush or old toothbrush for cleaning
• White vinegar for dissolving mineral deposits
• Small bowl or container for soaking parts
• Flashlight or headlamp for visibility under fixtures
• Water pump lubricant (food-grade silicone lubricant works well)
• Teflon tape for any fittings you disconnect
• Multimeter for testing electrical connections if needed

You'll also want to locate your RV's water system schematic if you have one, as this will help you understand the specific routing to your toilet and identify any inline components that might be causing restrictions. Most RV manufacturers include these in the owner's manual, but they're also often posted inside utility bays or near the water pump location.

Before starting any work, make sure to turn off your water pump and disconnect from city water to depressurize the system. You'll also want to have towels ready to minimize spills when disconnecting lines during your investigation. Having good lighting in your work area is crucial since much of RV plumbing work involves cramped spaces under sinks or behind toilets.

Walking Through the Fix

SAFETY WARNING: When working with toilet removal, be aware of sewer gas exposure and ensure proper ventilation. Always wear gloves when handling components that may have been exposed to waste water.

Let's start with diagnosing your toilet pressure issue since that seems to be your remaining concern. Begin by locating the water supply connection to your toilet - this is typically a flexible hose connection at the back or side of the toilet base. Before disconnecting anything, turn on the toilet flush mechanism and observe exactly how much water flow you're getting compared to what you remember as normal operation.

First, check the toilet's water supply line connection. Disconnect the supply line at the toilet end (you'll need to turn off the water and drain the line first). Once disconnected, turn the water back on briefly to check if full pressure and flow come out of the supply line itself. If you get good flow from the disconnected supply line, the problem is inside the toilet's water valve mechanism. If the flow from the supply line is also restricted, you've got an issue in the line itself or at an earlier connection point.

If the supply line has good flow, the issue is in the toilet's internal water valve system. Here's how to address this:

1. Remove the toilet from its floor mounting (this usually involves two or four bolts at the base)
2. Locate the water inlet valve mechanism - this varies by toilet model but is typically accessible once the toilet is lifted
3. Disassemble the water valve components carefully, noting their orientation for reassembly
4. Clean all valve components with white vinegar to dissolve mineral deposits
5. Check for any small orifices or passages within the valve that might be partially blocked
6. Use a small wire or needle to clear any visible blockages, being careful not to enlarge the openings
7. Reassemble the valve mechanism and reinstall the toilet, torquing bolts to manufacturer specifications

If the supply line itself has restricted flow, you'll need to trace it back toward the main water distribution system. Check each connection point along the line for restrictions, mineral buildup, or kinked hoses. Replace any damaged sections and clean all fittings before reassembling the system. toilet supply lines sometimes have inline connections or junctions that can accumulate debris. Follow the line back to where it connects to the main distribution manifold, checking for any inline fittings that might be partially blocked.

For your pump cycling behavior, this actually sounds normal given your setup, but let's verify everything is optimized. With 40 psi city water pressure, your pump should only need to run occasionally to maintain system pressure above its cut-in point. However, if you're noticing the pump cycles more frequently than expected, check for small leaks throughout the system. Even a very small leak can cause the pump to cycle repeatedly as it tries to maintain pressure.

To test for small leaks, disconnect from city water and rely solely on your pump and fresh water tank. Turn on the pump and let it build full pressure, then turn it off manually. Monitor how long the system holds pressure - it should maintain pressure for several hours without the pump needing to restart. If the pump restarts within an hour or two, you likely have a small leak somewhere in the system.

Since you've already addressed the main aerator screen blockages, make sure to establish a regular maintenance routine to prevent future buildup. Clean these screens monthly during heavy use periods, and consider the water quality at different campgrounds - some locations have particularly hard water or older distribution systems that will cause faster buildup in your RV's fixtures.

Beyond DIY Territory

While most RV water pressure issues can be resolved through the troubleshooting steps we've covered, there are several situations where you'll want to consider professional assistance. If you've cleaned all accessible screens and components but still experience significant pressure loss at multiple fixtures, you might be dealing with restrictions in the main distribution lines themselves, which often requires more extensive disassembly to access.

Professional help becomes necessary if you discover damaged or worn components during your investigation. For example, if the toilet's water valve mechanism shows signs of cracking or significant wear, replacement might require the correct part for your model (verify with dealer) and plumbing modifications that go beyond basic DIY maintenance. Similarly, if your pump continues cycling excessively despite finding no obvious leaks, the pump itself might need replacement or the pressure switch might require adjustment - both tasks that benefit from professional expertise to ensure proper operation and prevent system damage.

Another situation warranting professional attention is if you discover that your water pressure issues are related to problems with the main distribution manifold or if multiple supply lines show signs of restriction. This sometimes indicates that your RV's water system has accumulated significant internal buildup that requires comprehensive flushing or component replacement throughout the distribution system.

Cost considerations for professional work typically range from $150-300 for diagnostic and minor repairs, up to $500-800 for major component replacement or system modifications. However, the investment in professional service can be worthwhile if it prevents water damage from improperly diagnosed leaks or ensures that your system operates efficiently for years to come. Many RV service centers also have access to specialized tools for pressure testing and line cleaning that aren't practical for individual RV owners to purchase.

Moving forward, establish a preventive maintenance schedule that includes monthly screen cleaning during active use periods, annual inspection of all water connections, and seasonal system flushing to prevent the kind of buildup that caused your original pressure issues. This proactive approach will help you catch problems early when they're still in the DIY category rather than waiting until they require professional intervention. Regular maintenance will also help you become more familiar with your RV's specific plumbing layout and component locations, making future troubleshooting more efficient and effective.