Q: Closet Flange Connection to BW Tank

[micalk]

I need to rebuild the toilet platform which surrounds the BW Tank. From the way the toilet was installed it appears that the platform is about 3/8" short. The closet flange has a plywood spacer installed to raise it, and a similar spacer was needed to support the toilet. I want to rebuild the platform at the right height and put in a new toilet. But I'm having a bit of an issue with the disassembly. I don't know how to remove the closet flange from the black water tank. The flange is in remarkable shape, and I'd keep everything the way it is, except the MDF sides are in pretty rough shape.

There's two parts to a flange - the black center that is attached to the tank and seals to the toilet, and the metal ring that holds the toilet bolts and is screwed to the floor.

First, is the black center of the flange glued directly to the tank? Are black water tanks made of ABS and everything is glued together? Or are they HDPE like the fresh water tank and have threaded fittings?

The black center part of the flange has two indentations 180 degrees apart that look like places for inserting a wrench/tool to loosen/tighten it. Is that a correct assumption? I can fashion a tool that will work, but thought I'd ask the brain trust to see if I'm on the right track.

If the flange is glued to the tank do I have any choice but to replace the entire BW tank? Either that or build the top of the platform with two pieces that each surround half the flange when assembled.

Just want to know ahead of time what I'm getting myself into, and I don't want to destroy anything trying to take it apart the wrong way.

[micalk]

I'm very familiar with standard home plumbing, so all the DWV concepts are basically the same. It's a matter of the mechanics. First... Holiday Rambler, 73 Travel Trailer.

The BW tank is raised above the floor (hence the platform for the toilet) and this appears to be a direct connection to the tank. No room for piping between flange and tank. I would think the flange would be able to be removed without having to replace the tank.

I have no idea if the tank was ever replaced or if the flange was replaced (or both). Something was done, and now there's plywood spacers and what appears to be a fairly new flange in place.The metal ring of the flange has the slots for the toilet bolts cut into it. It's attached to the center and spins freely (i took out the screws that held it to the floor). It's the center plastic part that has indentations that appear to allow a type of spanner wrench to tighten/loosen it. Most fittings I am familiar with would have slip fittings and are glued but RVs are a different breed. I can do pictures later today.

[westend]

It sounds like what you have is a typical closet flange and a repair flange (the metal part). TYpical, stock plumbing for a closet flange is one piece of plastic that screws into the floor and also has slots for holding the toilet mounting bolts. There are usually no plywood spacers. It may be that there was a water leak at some point and a previous owner installed plywood to remedy the situation.

If you are seeing two square cut slots in the outer edge of the plastic flange, those are the typical slots for inserting toilet mounting bolts. They have nothing to do with unfastening the flange.

There are a number of installation scenarios with toilet plumbing. It may be that the flange and a section of pipe is threaded together and then enters the tank. It may be that the flange is glued to a section of pipe and is continuous into the tank. It may be that the drain pipe is welded or glued into the tank. It may be that the drain pipe enters the tank through a rubber grommet. In the latter case, the drain pipe and flange can be pulled out of the tank and a new grommet can be used for installation after you recover the work on the flange and supporting floor around it.

Pictures or at least a a mention of what you have regarding make, model, year of RV and toilet may bring more pertinent advice.