old flange flush with new subfloor?

[valontjej]

I am using my old fiberglass black tank and am trying to reinstall it underneath new subfloor. I have no idea how it was situated before but after I put it back(dryfitting) and the vent pipe on the tank line up with the pipe coming down I see that the flange is flush with the floor. This is how far I can push it up. It must have been similar before as the vents are in the right place. Am I missing something here or is there a way to reinforce the set up so I can install a toilet. I will of course secure the tank from underneath with straps, treated wood and sheet metal. Not sure exactly yet how I will do it but that is a fairly simple doing. I have learned so much from all of you since I purchased my 65 Overlander. I knew absolutely nothing previous to owning this one. And here I am part of the Airstream forum. Wow! Thanks for any advice. Monica

[Minno]

How is your flange attached to the tank? On ours, there is a threaded fitting for the toilet flange. The tank was installed under the floor, with the cutout in the floor big enough for the fitting only, and then the flange is screwed into the tank (with pipe joint sealant) until it rests on the top of the plywood floor. The flange is then screwed to the plywood floor. Here's a pic before the flange screwes were installed:



Was your flange glued to the tank already? It looks like it's high enough on the left side in the picture, but it also looks like it slopes down to the right. Is it possible to raise it with the tank so it's level, and slightly above the floor all the way around?

Chris

[valontjej]

thank you for replying. It is the original iron flange and I am hesitant to try to remove it. I have read that it can be very hard to get it out from the old tank without cracking part of the tank itself. So I had to cut the hole big enough to get the flange above the floor. I am heading over to the trailer in the evening and see if I can push it up further. I will also see if I cut a bigger hole where the vent is I may get it to come up a little higher. I will check closely to see if the flange is threaded in or. I'll take some more pics of the tank as I have to take it out anyway for adjustments e.t.c. Ah, the trials and tribulation of the black tank. Monica

[Aage]

It will be very difficult to secure your toilet with nothing to screw the flange to.

I believe it is important to remove the tank, separate it the flange from it, and repair the hole you made, or better yet, replace the sheet you cut for it. If replacing the sheet isn't practical, make a patch of plywood large enough to offer strong support for the flange, and make sure you fasten it in a structurally sound manner so that it becomes integral with the rest of your floor.

You have a very old tank there, but assuming that it is sound and you won't replace it, the thing to do is then to find a new flange to screw into the tank opening. Removing the old flange may require cutting it, or heat might help, too.

The new flange and the tank will "sandwich" the floor and give a good support for your new toilet.

Hopefully others will confirm what I am suggesting or give a better method, but with nothing to fasten the toilet to, you cannot proceed.

[Minno]

I agree with Aage. The flange needs to be supported, and the toilet mounts to the flange. I know they make flange repair kits though, and a google search for toilet flange repair kits, brought up this web site: Home

Maybe, if the flange is really glued onto the tank, one of their products might help. Also, if you break the flange while getting it off the tank, you can buy a replacement flange pretty cheaply.

Have you priced out a replacement black tank?

Chris

[valontjej]

thanks for replying. Yea, I had a hunch it would not work but tried anyway. I cut a new piece and was able to get it right,more or less. Since the tank is in good shape,no leak, I redid the exit valve system before I tried to figure out the flange issue. Two step forward and one back. Had to stop and focus on leaks Seattle eternal rain. Leaks along the ribs in the rear and window. No wonder the floor had rotted out. It was never fixed. Onward to drain reassembly and new pex water lines and securing the tank from underneath. Still pondering the best way without the metal box that housed the tank. It was totally rusted and broken.
More snow in the forecast and as much as I love Seattle come March I am so ready for drier weather. Thanks again for all the info. It is very helpful.

[68 TWind]

My old tank had a threaded hole on top with a treaded pipe that screwed into the top of the tank and the closet flange then screwed on to the the pipe after my black tank was in place. The the flange was screwed to the floor with SS screws. I had to replace my black tank because the old one was split at the top. On the new fiberglass tank, I had to drill the hole for the new fitting and glass in on to the back tank. There is about 2 inches between the top of the flange on the black tank and the floor level inside the trailer.
Be very careful with your measurements if you have not cut the hole in the floor yet.
Measure 4X and cut once. You want perfect. There is not a lot of wiggle room with the tank so you must get the hole in the subfloor exactly right. I put a layer of fiberglass around the edges of the hole and about a foot square around the flange before I put down my floor covering. Gives the floor a little extra stiffness and if there is ever a leak the wood is protected.

[Aage]

If your trailer is like my '74, the metal box you are talking about is structural. In other words, it is what holds up the tank.

Again, it is a part that can't be ignored, and must be fabricated with that idea in mind.

This might be the time to get a welding|fabricating shop to look at your trailer, and quote on a new tank support pan, complete with a sound method to fasten it in a way that will hold up the weight the tank will hold.

I'm sure that you don't want to be going down the road and have a bump set your tank free! In other words, there can be no "without the metal box that housed the tank" situation in your trailer.

Here is a drawing of the tank area on my '74 Sov. This shot doesn't include the mounting system for the support pan, but it hinges, so that tanks can be removed for repair or replacement. I am only showing you this to give you an idea of how they did it in later models. It would be a good idea to ask on the forums for someone with your trailer to show you a good diagram of the way yours should look, so that either you or the fabricator can make a plan.



Again, good luck!

[SummitAir]

I went through this same process. I would suggest a new black tank. Got mine from Inland RV. That way you can properly install a new floor flange plus the piece of mind knowing the one thing you don't want leaking will not leak. I would hate to have had to do it all over again. I just had my local sheet metal shop fabricate a new box for the tank with lip around the top for fastening to the subfloorand added new styrofoam all around that I got from Lowes. Just cut it to size. I replaced the 2 old angle iron black tank box supports with 2" angle iron, drilled new holes in the main frame and attached the angle iron there. I then installed a new sheet of belly pan sheet metal over all of this where I cut out toward the axles to expose it all. I overlapped this new piece with the existing piece, riveted them together and then sealed with metal tape. Last thing I added 2 more angle iron pieces under the tank box for added support that was not there before. In the end I feel confident that it is a much better install than the original due to the added and beefed up angle iron supports and the beefed up hardware connecting them.

[Aage]

There you go, that's what needs to be done,a dn it's not anywhere as difficult as it sounds.

I will repeat what SummitAir said: it is NOT a job you will want to do twice.

And before you buy a new black tank, have someone else look at the old stuck flange: it WILL come out, and allow a much better level of fitment than shimming small pieces of wood around that hole...

"Do it right, do it once" as my dad used to say. You'll be much happier in the end...

[SummitAir]

Yep. I'll add, I was able to back out my old floor flange and re-use it and I agree with above, it HAS to be mounted on top of the floor with the floor sanwiched between. Otherwise, when you sit, you will sag and eventually break with all of your weight on the tank itself. I also just got rid of the heat duct routed into the old box, don't need that in SW Mississippi. I covered the hole in the floor in the bathroom closet floor the duct was attached to by just screwing down a piece of sheet metal. Can't see it anyway. It really was not that hard, like you, valontjej, it was the unknown. I just took it slow and deliberate and when needed, I would ponder my next move over a well selected craft beer and proceed. I'll never regret the new tank. At the time mine was 40 years old and cracking around the gate valve neck and the gate valve lip seal has slipped allowing a slow flow through it. Replaced it also. It is a wonderful sight looking under the trailer after 5 days of camping and not seeing one drop on the cement pad from a leak. I would not secure the tank with straps and wood. Use angle iron running across from frame to frame where the new sheet metal box just sits in the angle iron. After positioning the box so it matched the floor flange hole up top I secured the box to the bottom of the floor using the 4 fabricated box lips which were just part of the box turned down and out. A box flange if you will. If you go this route get your sheet metal man to build the box a little bigger than the tank so you can slip in the foam insulation all around. Serves 3 purposes, freeze protection, slight slope toward the gate valve and cushioning. I then installed and attached the angle supports. The 2 angle iron pieces sit on the bottom lip of the main frame. I just slid them into each side of the main frame at an angle to get them over the bottom main frame lip. Slid them up to and under the front and back edges of the box and secured to the main frame. They fit very snug under the box. That box and tank ain't gonna budge!!!!! Went inside and screwed in the old floor flange then had a hallelujah beer!!! New toilet was a snap after all of that.