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  • Shelly Tschupp

Easy RV Water Leak Detection Test & How to Find it Using Air!

Updated: Feb 1

Easy RV Water Leak Test & How to Find it Using Air!
After running the test we we ale to locate a tiny leak!

Water can cause a lot of damage to the inside of an RV so avoiding leaks is pretty important. Once you get a big leak it’s easy to find, just follow the water trail, but is there an easy way to figure out if you have a small leak like a lose valve or connection, locate it and then fix it, long before it pulls away completely and causes damage? Yes, there is, and we’re going to show you how!


My husband’s expertise is actually in the Marine industry, and while that is not an RV, many of the systems used are somewhat similar. The freshwater system used in the Cabin on a boat is much like that used in an RV. Both are enclosed pressurized systems. His expertise on this came in handy more than once when our RV had a leak. Rather than laying down paper towels or powder to try and locate it, a leak that might only be leaking under certain conditions he utilizes the internal water pump and air to find it fast for immediate repairs.

Easy RV Water Leak Detection Test:

You can use your freshwater tank and pump to test for leaks simply by disconnecting from the RV Park water connection, adding some water in your freshwater tank, then turn on your freshwater pump. That pump will initially kick on to pressurize your system and you can hear it running while it does this. If you can’t hear it running, open the panel covering it so that you can hear it run. Once the system is pressurized that pump will turn off and be silent. If the system is pressurized, as it should be, that pump will not turn back on until you use some water!


You will know your system may have a leak if either of these situations occur:

  1. Your turn the freshwater pump on and it never turns off because it can’t obtain pressurization.

  2. The freshwater pump turns off but turns back on every so often even though no water has been used indicating a small leak. We like to do a 30 minute test on this with our RV every quarter or before we go on a trip if we haven’t used it for a while. We sit near enough to the pump to hear it if it kicks on, we do this for about a half hour.  It’s a good time to catch up on emails or an article while we quietly wait.


There are some things to keep in mind:

  • Appliances that you have connected to the water system need to be turned off/valves closed to prevent false results: ice makers, clothes washer, dishwasher & water heater valves during the test.

  • Make sure everyone else knows not to turn on the water when you are doing the test.


Ok, so you did the test and ... unfortunately your pump is cycling back on every 12 minutes, which tells you it’s losing pressure somewhere in the lines or connections. So how do you locate the leak to fix the problem before it becomes a big leak and mess in the future?

Find the Leak with Air pressure!


Tools You Need To find the leak:

  • A small oil free air compressor tank that has at least 25 PSI, you might already have one around to refill your RV or Truck tires with air.  You need an air hose and a Blow Out Plug to connect to your City Water (this bundle from Craftsman includes the Air Compressor & Blow Out Plug.  

  • You may need a screwdriver to remove wall panels that cover your water lines so you can hear any leaks.


Air compressor and blow out plug to find leaks in the RV.
Craftsman Air Compressor Blow Out Plug Bundle

Important Step: If your water heater isn't in bypass please put it in bypass. Please adjust the air compressor outlet pressure to 25-30 psi. Initially when you connect the air compressor to the city inlet valve there is some pressure drop from the compressor. wait for it to stabilize and note the pressure. If the pressure continues to drop there is a leak to go find. if your not sure if a fitting is leaking some soapy water can help. Once you find the leak you can try several methods to repair depending on where it is. If the threaded compression fitting is dripping try to tighten with your hand first. Remember it's plastic! If the leak is around a fitting with a clamp you may want to try to disconnect it and check for a cracked fitting. The RV and Marine industries use a lot of plastic fittings that may crack.


To do a Leak Search:

  • Double check that all of your sinks, shower, and any appliance water handles/knobs are turned off.

  • Turn off the Water Heater and Bypass it so it is not part of the test.

  • Go around the inside of your RV and open any areas where the water lines are located behind them for easy access during the search: that may include removing any wall panels covering the lines, opening cabinet doors, pulling out drawers, and removing the temporary wall in your storage compartment where the lines connect to the water management panel.

  • Turn off any radios and TV’s because you need to be able to hear the air escaping from the lines to locate the leak.

  • Fill up the air compressor tank to 100% for the test, set the pressure to 25 to 30 PSI and connect the blowout plug to your RV outside City Water Connection. Make sure it’s a strong connection (if you hear an air hissing sound at the connection try changing the washer to get a solid airtight seal).

    • For RVs with a typical freshwater connection, you’ll attach the blow-out plug directly to the city water connection.

    • For RVs with a permanent hose on a reel, you’ll attach the blow-out plug to the end of the hose.

  • Once you have a solid seal refill the compressor tank to 100%, make sure the PSI is set to 25 to 30, reconnect the blowout plug. Go inside the RV and go to every water line and listen for a moment for a hissing sound of escaping air and look for tiny sprays of water that remained in the lines after draining the freshwater tank. If you see or hear any, that’s a leak you need to fix.

  • If the compressor runs out of air before you are able to finish your walk through, refill the compressor tank and continue your search.

  • If the compressor does not lose any pressure during the test consider if anything was turned on when you did the first test that is now turned off including the water heater, appliances that draw water directly (filter systems, ice makers, dishwasher, clothes washer, water heater, etc.). If there is a leak and the compressor tank started at 100% it will have lost some of that pressure as air escaped the system.


If you know you have a leak but could not find it most likely it is in a location you can’t see or get close to. Many RV’s have lines run in the enclosed under belly, or below the floor, or even under the slides. At this point consider installing some water leak detectors to alert you if the leak increases and water collects in key areas like: under the sink, in garage storage, etc. until you have the time to research how to access those more difficult locations.  


High Rated Leak Detecting Water Sensor:

Govee Wifi Water Sensors low priced with 4.5 star reviews!

Ring Flood Freeze Sensor works with Wifi, Alexa however requires an additional Protect Service

We hope this helps you locate those pesky leaks before they become bigger one’s and avoid some of the damage that can happen!


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