Sunday, May 28, 2023


Learn all about RV underbelly plumbing leaks

One of the most frustrating things for an RVer is having to deal with a water leak underneath the RV in the underbelly area! And if you didn’t know, this is a dreaded repair for any RV technician. From sewer leaks, to dump valve cable failures, water lines, waste tank, gray tank, fresh water tanks, and the hundreds of fittings, all leak at any time due to use and wear and tear from traveling.

As you will see in the pictures, there is a mess of wires and plumbing that we have to contend with when trying to pinpoint the leak. Underbelly leak repairs can be like looking for a needle in a haystack.

California RV Specialists techs working together to remove the underbelly and secure everything in the way in order to test for leaks.
Example of wiring and hose that are just floating around in the underbelly.

There are several contributing factors that can cause an underbelly leak:

  • Supply lines could have been improperly run and were not secured into place.
  • Road vibration and flex cause wear and tear/rubbing underneath the unit.
  • Normal use of the water pump causes vibration.
  • Improper use by not using a water pressure regulator.

Why is this repair such a nightmare?

  • On average, there are 200+ water line connections throughout the unit.
  • Heat ducting and electrical wiring are often in the way.
  • In most cases, we also have to pull LP lines, power/manual leveling jacks and/or Styrofoam around pipes in order to inspect an area and make repairs.

If you are experiencing a leak, there is some helpful information that you can provide that will save your technician some time, which hopefully will also help save your pocketbook:

  • Is the leak black, gray or fresh water?
  • Is the leak hot or cold water?
  • Was the tank overfilled or is it a drain valve leak?

Knowing this information will help locate the leak faster!

Finally, should you end up in a position of needing an underbelly leak repair, whether it is you or an RV technician, this is your excellent opportunity to do the following while having the underbelly removed:

  • Add additional insulation.
  • Add additional spray foam where needed. This will help seal off any penetration from the floor to the house which will help reduce the interior heat or cooling loss. In addition, this will also help reduce the path of entry for pests, rodents and dust/dirt.
  • Secure all water lines and electrical wiring that is floating around to help prevent future leaks.
  • Secure and retape all heat ducts and piping.
Example of the average RV underbelly open.

If you are doing these repairs yourself, here are some links to items you’ll need to complete the job:

More from Dustin

Read more of Dustin’s articles here.


Dustin Simpson
Dustin Simpson
I have worn many hats in the RV industry through the years. From an RV Technician, Warranty Administrator, Parts Administrator, Parts Manager, Service Manager and now Business Owner. I have even been deemed an RV Expert by the California court system, working on behalf of the customers, dealers, and manufacturers. My repair facility has been servicing customers at the same location since 2003. What sets us apart from the dealerships is we are here to fix and maintain what you have, and not sell you a new one. Whether you own a million-dollar unit or an entry level, my message to you will be the same, it needs to be maintained.


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Tom H.
16 days ago

I helped a friend locate and repair a leak in his underbelly. You’re right, wires, ducting, and water lines every which way. Not to mention a lack of insulation or all the insulation to one side or the other. While we were under there we tied up all the wires, ducting, and water lines as well as added a lot more insulation.

16 days ago

What a nightmare, if rv manufacturers gave a diagram of electrical and plumbing, it might help?

Tom H.
16 days ago
Reply to  Diane

The problem with that is they really have no diagram. There’s a rough idea or plan but it’s not built specifically to that plan. It’s more of a 30,000ft view so to speak. I equate it to a RV Park or campground map. It doesn’t really indicate what the property looks like.

Dave Pellegrino
19 hours ago
Reply to  Tom H.

That’s the problem… No requirements for this specific info. If today’s cars can have detailed schematics and wiring diagrams, surely an RV can have the same. They are not any more complicated than today’s vehicles. If these RVs manufacturers thought it out and used uniform diagrams & schematics for each unit we’d all have a much better RV and RVing experience. NTHSA needs to step up and require this. This 30k ft view is ridiculous for building anything.

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