House Calls with the RV Doctor
By Gary Bunzer
Dear RV Doctor:
I have a Sportscoach III on a P-30 chassis. I need to either shorten or modify the 3-inch down tube connecting the toilet to the black water tank. The problem is that the tank is oddly shaped, because part of it sits over the tag axle and is very shallow. Unfortunately, that is exactly where the waste dumps from the toilet. The result is that the tube ends about 1½ inches above the bottom of the tank (short section). Because the tank never fills to this level, even when full, the tube plugs quickly and virtually every time it is used. So, I need to either add an elbow to the down tube or cut it off flush with the tank bottom. But how do I get the tube out of the tank? Does the flange unscrew? Or is it glued directly to the tank?
RV Doctor: Mark, indeed it is a shame when a floor plan dictates the location of such fittings with a negative result. It just so happened that the floor plan mandated the toilet be positioned over the tag axle on your coach. Most 3-inch toilet drains flow straight into the holding tank. Unfortunately, yours dumps right onto that “shelf” at the shallow end of the tank. Toilet drains may be diverted to a location farther over on the top of the tank, but doing so requires enough clearance for three 45-degree turns in the ABS pipe (never use a 90-degree elbow for the toilet drain). This diversion is possible only if you have enough vertical clearance between the bottom of the flooring and the top of the holding tank to position the three 45-degree elbows and the necessary connecting pipes. To be sure, purchase short-turn, 45-degree elbows; lay them out on the floor; and measure the minimum height required.
The toilet and the floor flange must be removed in order to drop the holding tank. Also, the termination assembly and the vent pipe must be disconnected from the tank before it can be removed. Some flanges and toilet drains are glued, some are threaded, and some use a simple friction seal with the downpipe inserted into a rubber grommet at the top of the tank (see photo). The downpipe should never extend into the holding tank more than 3/4-inch. Extending farther into the tank is possible only with the rubber grommet even though there is a lip on the inside of the grommet. Remember, it is only rubber, so a “too long” pipe can be pushed past the lip and forced farther into the tank. This may be what happened on yours. If your downpipe is threaded or cemented, it cannot extend too far into the tank, because the threads and the seat of the fitting would limit its travel.
First remove the toilet and then the screws that hold the flange to the floor. Try to “unscrew” the flange and downpipe together as one unit. (A simple removal tool can be made by using a short piece of 1-inch-by-3-inch shelving material with two 3/8-inch holes drilled through it that match the spacing between the two existing closet bolts in the flange. After the toilet has been removed, place the board over the closet bolts and rotate counterclockwise.) If it will not rotate, it is probably cemented. If cemented, the drain pipe will have to be cut between the bottom of the floor and the top of the tank. If you have the rubber grommet or the threaded fitting into the tank, the flange and downpipe assembly will twist free and can be removed from inside the bathroom. Careful measurements can then be made to determine whether the pipe extends too far into the tank and/or whether you have the needed space to install the 45-degree ells to move the inlet to a deeper section of the tank.
If you have the clearance for the 45-degree fittings, then you can drop the tank, cut a new opening in the tank, and have the old inlet plastic welded with a patch. Check to see whether your local RV shop indeed has a plastic welding unit. Welding will be the only way to guaranty a leak-free patch. Then reinstall the tank using the 45-degree elbows; connect the termination assembly and vent. Be sure to fill the tank with fresh water all the way up and into the toilet bowl to test the integrity of the modification.
Weeping Out Loud
Dear RV Doctor:
I have an older American Appliance water heater on my 1985 coach. The burner won’t shut off, and the pressure/temperature safety valve then does its thing, but it doesn’t just “weep” — it goes hysterical. Water jets out of the valve as fast as the city water is coming in. I have reviewed all your columns online but haven’t seen another problem like this. Help!
RV Doctor: Jim, as long as your incoming water pressure is not abnormally high, it could be something as simple as a faulty P&T relief valve. But if your pilot-type water heater is not properly shutting off the main LP burner when the temperature of the water has reached the limit of the control valve thermostat, then that safety valve is operating properly. If you manually shut down the water heater, does the P&T valve finally snap shut at some point? If so, then most likely the integral thermostat itself is faulty as well as possibly the ECO (energy cut-off) device encased inside the very tip of the sensor (that portion immersed in the water). Two types of ECOs were used in those older pilot model RV water heaters; one was a bimetal thermal switch of sorts (pictured) that should eventually reset itself once the water temperature cools. The other type was electronic by design and will not reset. It’s a one-time safety and once it’s tripped, there is no way to regain continuity through the device. If the ECO is the culprit, chances are the whole control assembly will have to be replaced. As old as that water heater apparently is, however, I would consider replacing the entire unit and obtaining a new warranty, etc. The newer models are much more efficient and offer the best in the latest technology. You certainly would not want to invest in a costly repair only to have the inner tank rupture in the coming months. I’d vote for a new unit if the main control valve is at fault.
Dear RV Doctor:
Can ceramic tile be installed in a motorhome? If so, what type of flooring is best to put down?
RV Doctor: Clark, yes indeed, ceramic tile can be successfully set onto a motorhome floor. Proper preparation is the key. The surface must be leveled and all seams in the underlayment must be smooth, with even transitions between them. Most home builder supply centers, such as Lowe’s or Home Depot, will have all the preparation materials you’ll need. Either 5/8- or 3/4-inch plywood works very well as an underlayment. It seems motorhomes built on the larger chassis fare better with tile since the upper flooring is somewhat stiffer than those of a standard type A design. There has been some evidence of cracking in the grouted joints with smaller RVs, which tend to flex more, but with the proper materials and workmanship, ceramic tiles add much to the individuality of your RV. Marginal weight restrictions may have to be considered on those RVs approaching their limit. You might have to do some math first.