Multiple Pump Switches
Dear RV Doctor:
I need to add a third water pump switch in the toilet area of my RV. As of now I have a three-way witch on the master control panel and another three-way switch in the outside plumbing compartment. Is it possible to add another switch, for a total of three?
Lance Jones, Colton, California
Yes, it’s possible to add a third water pump switch, but the new switch must be a four-way switch (four terminals, instead of three) rather than an additional three-way switch. And please don’t confuse a three-way switch or a four-way switch with a switch that simply has three or four terminals. They must be internally constructed specifically as three-way and four-way switches.
As your RV is currently equipped, you have two three-way switches in the electrical circuit that powers the water pump. When adding a third switch into that existing circuit, you’ll have to obtain a new four-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’s “hot” line is routed and where it is connected into that circuit. The “hot” wire could connect first at the water pump itself (not likely), or it could be fed first to one of the three-way switches (most likely).
Without going into all of the possible wiring methods, I’ll provide instructions for adding the new four-way switch, assuming the “hot” wire is currently connected first to one of the two existing three-way switches. While my description may sound confusing, the accompanying diagram should help.
When adding more switches, it is necessary to “insert” (electrically speaking) a new four-way switch between the two existing three-way switches. Literally any number of four-way switches can be added to any circuit as long as a three-way switch begins and ends that circuit. Theoretically, you could have a hundred switches for the pump, the only requirement being that the first and last are three-way switches and all the rest are four-way switches. Also remember, you will be switching only 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 you have a hard time locating the existing wiring or have difficulty determining how the existing switches currently are 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 three-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 three-way switch is what ultimately connects to the water pump. A four-way switch does not have a “common” terminal but instead has color-matched pairs of terminals. Remember, a four-way switch is not JUST a switch with four terminals; it’s internally constructed as a specific four-way switch. As seen in the diagram, the two traveler wires (those wires that run from switch to switch) from the first three-way switch connect to one of the color-paired terminals on the four-way switch. And the traveler wires from the four-way switch connect to the two outside terminals on the last three-way switch. It is important to connect the traveler wires correctly at each four-way switch.
Here’s hoping the RV manufacturer used different colored wires when installing the two three-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 decide which approach is best.
Holding Tank Cable Pull
Dear RV Doctor:
I own an older Holiday Rambler motorhome, and my black holding tank cable, the one used to dump the holding tank, broke at the valve. How do I repair this?
Larry Earwood, Dayton, Ohio
You could attempt to repair the broken cable pull on the termination valve, but I’d recommend that you instead install an electric holding tank gate valve and forgo installing a mechanical cable or rod. Some old-school designs are simply best left to obscurity, and I think after you check out the information found at www.drainmaster.com, you will agree.
Since any repair will necessitate gaining access to the existing valve, I suggest you simply install the electric valve and forget about the cables. With the hands-free waste gate installed, opening the valve to dump requires just the push of a button!
Begin by removing the existing valve (sandwiched between two adapters at the tank outlet) and install the new valve. Orient the valve vertically; the more vertical, the better, even if it’s only slightly upward. In fact, EVERY termination valve should be mounted in this manner to prevent waste and crud from entering the body cavity of the valve. This will help 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 downward, yet it is a very common occurrence.
Next, route the wiring harness to a convenient location inside the plumbing bay or compartment. A security lockout panel is also required, but the installation is not difficult. In fact, installing this valve can be accomplished easily by most RV handypersons. That is, as long as the cable broke while the valve was in the fully opened position and the tank is empty. If the cable broke and the holding tank is full, performing a repair or installation presents a greater challenge.
Perhaps the tank can be pumped out through the toilet by a local septic company. If not, you may want to take the motorhome to a local RV service shop to have the installation done for you. (Although the service technician likely will check the tank before beginning the job, be courteous and tell the service center whether the tank is full when you deliver the vehicle.) 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 electric valve. By the way, for the optimum setup, replace the gray tank valve at the same time.
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