RV Construction - Interior Wall Removal - UPDATE!

I have an older RV I just bought. It is kind of a project for me and one of the things I'd like to do is open up the bathroom area in back. But to do so I have to remove a cabinet and two short inner walls. Not having worked on motorhomes before I am wondering if I can just remove the walls or if they serve some load bearing function. They are located on the back wall and don't seem to do anything but divide space, but I don't want to make a major mistake.
Joel, (Taylors, SC) 

Joel, there are no load-bearing interior walls in the motorhome. You are correct; they are there simply to create separation between areas of the RV and are considered basic partition walls. And I’m guessing every one will be hollow walls at that. You’ll probably also find screws coming into the cabinets from the outside in. These can simply be hack-sawed or cut with a Saws-All. 

Update from Richard Miller: Gary, you recently advised that it was OK to cut an RV interior wall and that the walls in RVs were not load bearing. I agree about the load bearing statement, but I also know that I have black/gray vent pipes and wiring to switches and thermostats located in the interior walls of my 5th wheel. They are not all located in the outside shell walls. The questioner should be advised to proceed with caution after careful examination.

Thank you Richard! You are exactly correct and you may have saved Joel some headaches. Indeed if the partition wall exhibits any type of electrical component, it may be necessary to re-route some wiring before removing the wall itself. Also, if the partition wall appears to be a couple inches wide or more, there could be some vent piping stashed behind there. As Richard mentioned, proceed with caution if any doubt exists.

Adding a Third Water Pump Switch in the RV

I need to add a third water pump switch in the toilet area of my trailer. As of now I have a three-way switch on the master control panel and another three-way in the outside plumbing compartment. Is it possible to add another for a total of three, just for one water pump? Thanks!
Lance, (Colton, CA)

The short answer Lance, is yes, it is possible to add a third water pump switch, but it’s necessary for the new switch to be a 4-way switch (four terminals, instead of three), rather than simply an additional 3-way switch. And please don’t confuse a 3-way switch or a 4-way switch with a switch that simply has three or four terminals! They must be internally constructed specifically as 3-way and 4-way switches. As the RV is equipped now, you have two, 3-way switches in the circuit to power the water pump. When adding a third switch into that existing circuit, you’ll have to obtain a new 4-way switch. Be sure it’s rated to carry the DC load of the water pump. 

What’s interesting is that there are numerous ways to configure all three switches, depending on how the pump “hot” line is now routed and where it is connected into that circuit. The “hot” wire could connect first to the water pump itself, (not likely), or it could be fed first to one of the 3-way switches (most likely). Without going into all eight possible wiring scenarios, I’ll provide the instructions for adding the new, 4-way switch, assuming the “hot” wire is currently connected initially to one of the two existing 3-way switches. Now this may sound confusing, but the below diagram should help. 

It will be necessary to electrically “insert” the new 4-way switch in between the two existing 3-way switches. Any number of 4-way switches (literally), can be added to any circuit, as long as a 3-way switch begins and ends that circuit. Theoretically, you could have a hundred switches for the pump. The first and last would have to be 3-way switches and all the rest would be 4-way switches.

Also remember, you will only be switching the “hot” wire to the water pump; the ground wire does not connect to any switch. Just be sure you have a good, frame ground connection for the water pump and the battery. If it’s too restrictive to locate the existing wiring or if you have difficulty in determining how the existing switches are now wired, another option is to simply start afresh with newly run conductors. Take a look at the existing water pump fuse; if it’s a 15-amp fuse, you’ll need to run 14-gauge wires, if it’s a 20-amp fuse, you’ll need to use 12-gauge conductors. 

The common, center terminal of a 3-way switch will be colored differently from the other two terminals on the same switch. Some may even be labeled. Typically, the positive feed wire from the fuse panel is connected to this common terminal on the first switch in the circuit. Likewise, the common terminal on the other 3-way switch is what ultimately connects to the water pump.4-way switches do not have a “common” terminal, per se, but instead, has color-matched pairs of terminals. Remember, a 4-way switch is not JUST a switch with four terminals; it’s internally constructed as a specific, 4-way switch.

As seen in the diagram above, the two traveler wires, (those wires that run from switch to switch), from the first 3-way switch connect to one of the color-paired terminals on the 4-way switch. And the traveler wires from the 4-way switch connect to the two, outside terminals on the last 3-way switch. It is important to connect the traveler wires correctly at the 4-way switch. Hopefully, the RV manufacturer used different colored wires when first installing the two, 3-way switches you have now. That would make your task much easier. Oftentimes, however, it may prove easier to just run all new wires. You’ll have to be the judge on that one!

Green RVing?

I have a relatively new coach and have noticed all the gas system copper tubing lines are corroded green. The areas that are the worst are where the mounting brackets and support clips are screwed to the frame. Could this be caused from stray currents of electricity? The unit was bought brand new six months ago and unfortunately the manufacturer has filed Chapter 11 and will not warranty this problem. I am concerned for the safety of my family. I have turned off the valve on the LP container. Any ideas on how the resolve this problem?
Alan, (Deltona, FL)

First of all, Alan, allow me to calm your fears regarding stray electrical currents. Chances are, that is not the case. A series of specific tests by a certified RV technician can confirm that, however, if you need more assurance. But it is not uncommon for copper tubing to oxidize at a rapid rate in certain areas of Florida. I grew up in Florida and I didn’t know copper tubing came in any other color but green until I eventually moved to California! The green patina of your existing tubing is also exacerbated by the mounting methods  employed by some RV manufacturers. A process called galvanic corrosion takes place between any two dissimilar metals. For example, your copper tubing is most likely secured to the steel frame and held in place by either aluminum or zinc-plated clamps. Further accelerated by the salty Florida air, (well, maybe not in downtown Deltona, more so at either coast), the non-ferrous copper will quickly turn a shade of green. Serious oxidation, typically on older coaches, may cause eventual pitting, pin-holes and possible LP leaks, but on a unit six months old, this is doubtful. 

To be sure, however, I would suggest a Certified RV technician perform a gas system, timed pressure drop test. This will verify that no leaks are present anywhere in the system. At the same time it can be verified that the correct delivery pressure is being fed to the appliances. This is a very common and relatively inexpensive procedure which must be performed annually anyway.

To minimize the effects of galvanic corrosion, here are a few things you can do. First, insulate the tubing by wrapping all exposed copper in slit foam insulation wrap or black electrician’s tape. Another preventive measure is to replace the metal clamps used to secure the tubing to the frame with insulated clamps. One with a rubber insert whereby only the rubber portion makes contact with the tubing. You might even add a few extra wraps of electrician’s tape around the tubing at each clamp position. At the same time, place a thick washer or two behind each clamp so there remains a gap between the tubing and the steel frame. The key is to make sure the tubing does not physically contact the steel frame at any point. Where copper tubing branches off and routes up and to the individual appliances, make sure grommets are in place anywhere the tubing passes through the frame, floor or wall. Hope this helps!

TPO Tear on RV Roof

I’m considering purchasing a used Cruise Master motorhome with an 8-inch tear in the TPO roof. It’s not too deep, but deep enough to get your fingernail in. Is this repairable on TPO? I’m also concerned about a soft spot about six to eight inches in diameter just off the center-line. The reason I ask is the roof warranty is not transferable so nothing is covered if I buy this motorhome. What do you think?
E., (Baltimore, MD)

E, for just about any roof repair, as you might have noticed, I recommend Eternabond sealing tape. The only precaution is that the repair area be clean and totally dry. I’ve had success with this product on every type of roofing material from aluminum, EPDM (rubber), TPO and fiberglass. 

As far as the soft spot, it could be evidence of a leak with possible substrate damage. The only way to know for sure is to remove a portion of the TPO and carefully inspect the plywood substrate below. 

If you really like this coach in all other aspects, I don’t feel this should be a deal breaker. It could, however, be a strong negotiating chip. Keep a close eye on the soft spot after you repair the tear. If it continues to grow in area, or become softer, it may be time to take a deeper look at the substrate. All, however, is repairable, in my opinion. Be sure to inspect every component and seam on the roof. You’ll be able to use Eternabond just about everywhere up there.

Holding Tank Cable Pull Failure

I own an older Holiday Rambler motorhome and my black holding tank cable broke at the valve. The one I pull to dump the toilet holding tank. How do I repair this?
Larry, (Dayton, OH)

Larry, my alternate repair fix for those dreaded broken cable pull termination valves is to install a Drain Master electric holding tank gate valve and forego any propensity for repairing the mechanical cable or rod. Some old-school designs are simply best left to obscurity! Check out this website:

You’ll have to gain access to the existing valve anyway. And since you’re going to that extent, simply install the electric valve and forget about cables. Just push a button! Just remove the existing valve (sandwiched between two adapters at the tank outlet) and install the new electric valve. Make sure the valve body is oriented vertically; the more vertical, the better, even if it’s only slightly upwards. In fact, EVERY termination valve should be mounted in this manner to avoid waste and crud from entering the body cavity of the valve. This will eliminate the possibility of the residue drying out and putting a bind on the sliding gate portion. This is typically why termination valves fail in the first place. RV manufacturers simply should not mount termination valves horizontally or angled downwards, yet it is a very common occurrence. 

Next, route the wiring harness to a convenient location inside the plumbing bay or compartment. In fact it’s easily accomplished by most RV handypersons….if the cable broke while the valve was in the fully opened position, that is! If the holding tank is full, however, it presents a greater challenge. Perhaps the tank can be pumped out through the toilet by a local septic company, but this is difficult at best. Holding tanks can implode through the efforts of an unknowing honey bucket operator! Perhaps a local RV service shop can do the installation for you. 

Removing the broken valve can be a messy proposition if the tank contains waste. Some RV facilities have a dumping area that employs a huge funnel device whereby the valve can be removed and the contents allowed to flow into the funnel and into the sewer inlet. Pro RV shops will have their methods, but the important thing is getting the old valve off, flushing out the tank completely and installing the new Drain Master. By the way, for the optimum set-up, replace the gray tank valve at the same time.