Inside the Belly – Keystone Cougar 276RLSWE Fifth Wheel


Our 2011 Keystone Cougar 276RLSWE Fifth Wheel has a black chloroplast (plastic like material) layer attached to the bottom with many 3/8 nut headed self taping screws. Since I had to undo a fair amount of this material to complete a recent installation of a remote headphone jack I decided this would be a good time to explore exactly what was underneath. The Keystone trailers to my knowledge don’t issue a blueprint or any plumbing and wiring diagrams to the end consumers so maybe this post will help a fellow owner in the future.


The easiest side to peel back is the drivers side. The passenger side of the rig is where they run the propane piping making it a little more complex to remove some screws and the covering. I undid most of the screws on the drivers side and peeked in with a flashlight getting a feel for where the most critical and likely to need service things are located.  I then cut some access flaps into the chloroplast below these areas.  The factory had already done this under the slide motor to provide access to the it in case of having to manually move it with a wrench or drill.  I followed their method of making three cuts of a square leaving the fourth side intact. After using the access ports they can be sealed with a product called Gorilla tape. Works really well! I opened access ports under the grey and black tank valve areas and under the fresh waste tanks where the fill and water pump plumbing is located. I figure if a leak happens these are the most likely areas I will need to get at.

Water and Waste Tanks

What did I see, well the bulk of the space is taken up by the one fresh water tank and the three waste tanks: Galley gray, Shower and Bath Sink gray and Black. I could read the model numbers off tags on the tanks and by looking them up online determine that the three waste tanks were all rated at 38 gallons and the fresh was 60 gallons. The Shower/Bath Sink gray and the Black tanks are very close to each other with 4 inch outlet pipes quickly joining together into a Y connection and then running out to the sewer output. It looks like a smart setup as after you empty your black tank and leave it’s valve open a good wash of water will enter when dumping the gray. The Galley tank is a good distance away above the trailers axles and joins the sewer output with around 4 feet or so of 2 1/2 inch pipe.

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The bulk of the electrical wiring is located in a channel running front to back just inside the drivers side. A bunch of wires also branch off right near the Galley gray tanks dump valve and head straight across to where they can feed up into the converter, fridge, and furnace area.  This would make a good route for a solar panel upgrade. Wires could come off the roof and down through the fridge roof vent then follow this existing wiring route back to the batteries. All the tank level indicator sensors and wires are located on this drivers side of the four tanks.


A few other things I could see down there were:

  • The whole area is insulated by a 1/4 inch reflective bubble type material.
  • There is a 2 1/2 inch furnace duct protruding down between the black and galley tanks on the passenger side.
  • Much of the space is just empty, might be worth shoving some bats of insulation in there.

Crude Drawing of the layout

Tanks And Wiring Layout

Tanks And Wiring Layout

Video Clip Showing the Inside View

Hopefully this can help another Keystone Cougar 276RLSWE Fifth Wheel owner when doing  repairs or mods on their rig.

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  • ken

    black h2o tank plugged-ant hints?

    • Is it the same tank layout as mine? If so you could fill the opposite gray tank and then open both valves and hopefully the flushing gray water might loosen the clog in the black tank.

  • Bruce

    Pump quit working/2013 cougar / help !

    • Hi Bruce it’s likely one of a few things. Pump could be defective, switch bad, blown fuse, or faulty wire. I would first look for a fuse, either in the fuse panel or maybe an inline one near the pump itself. If fuses OK then you need to check if 12 volts is making it to the pump checking with a multimeter or 12V tester light. That way you can determine if the its the pump bad or wiring has an open circuit somewhere.

  • bill

    Ray. My son is trying to replace the black water valve. He is under the belly but cant get the old valve out to tight. Any suggestions?

    • Not sure why it would be tight, unless they used some sort of plumbers cement when they installed it.
      You could check out this Youtube video, may help –
      I have to do mine soon as I noticed a crack where the pull rod enters the plastic.