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Friday, October 23, 2009

Toilet Tube Troubles

I have a Sportscoach III on a P30 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 1-1/2" 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?
Mark, (Portland, OR)


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 rig. 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 further over on the top of the tank, but it requires enough clearance for three, 45-degree turns in the ABS pipe. Never use a 90-degree elbow for the toilet drain. This 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 and 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 also 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. The downpipe should never extend into the holding tank more than three-quarters of an inch. Extending further into the tank is only possible 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 further 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 holding 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 X 3 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 counter-clockwise). 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 if the pipe extends too far into the tank and/or if 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 if 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.

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