The toilet in a mobile home connects to the main drain in the same manner as toilets do in framed houses or manufactured homes. The flange is anchored to the floor through anchor screws and holds the toilet in place through retaining bolts.
The piping beneath the toilet in a mobile home is held in place with suspension lines. Replacing the flange is a good time to check the pipes for stability beneath the mobile home. The project might require climbing beneath the home, and you better prepare for some tight spaces and unpleasant conditions. The good news is that if the pipes are fine and the job involves simply replacing the flange, you won't have to crawl under the trailer again because you can do everything from the comfort of the bathroom.
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Start by Removing the Toilet
Turn off the water shutoff valve and empty the tank by flushing once or twice. Put a bucket under the water supply connector, remove the connector with adjustable joint pliers and let the residual water pour into the bucket. Remove the two screws holding the bottom of the toilet to the flange using your pliers, lift the toilet off and set it aside.
You now have a clear view of the flange and should be able to assess its condition, although you may have to scrape away some wax. If there are no cracks or other damage, and the main problems were sewer smells and water on the floor, chances are you need to use a wider wax ring when you replace the toilet because the previous one probably wasn't making a good seal. If the flange is damaged, though, you need to replace it.
Removing the Old Flange
The toilet flange is screwed to the subfloor, but it's typically also glued to the waste pipe, although not always. When you remove the screws holding it to the floor, try lifting or prying it up, but don't force it. If it moves fairly easily, you should be able to remove it, but if it won't budge, it's glued to the waste pipe and forcing it might break the pipe at a place that would require another unpleasant trip underneath the mobile home. At this point, you'll have to cut it.
One option is to make an inside cut using a rotary tool and a circular saw accessory. The cut should be made 2 to 3 inches below the flange opening. A more elegant and effective method, however, is to use a Flange Off toilet flange removal tool, but it works only for flanges that fit over the waste pipe, not inside it. It consists of a hole saw that matches the inside diameter of the flange and a guide to keep it centered, and you operate it with a drill.
You can always use the method of making parallel cuts through the inside of the flange with a reciprocating saw to create a series of strips that you can chisel away. This job must be done cleanly because any glue or plastic residue that remains will prevent the new flange from fitting.
Setting the New Flange
The type of flange you need depends on the diameter of the waste pipe to which it's attached, which is either 3 or 4 inches. Purchase a replacement flange with the same diameter that fits either over it or inside it. Some flanges are designed to be glued to the waste pipe, but some, such as the Oatey Twist-N-Set, have rubber gaskets that create an efficient seal without glue. Glueless flanges are easier to install and remove and are the better option for a mobile home.
To complete the flange replacement, insert the flange pipe into the waste pipe and push down on the flange until it's flush against the floor. Screw it to the subfloor using the screws that came with it, and the flange is ready for the toilet.