Sway-back Black Tank

[Chuck]

So, my new black tank arrived a few weeks ago (waiting for spring to resume renovation work). I'm a little bit concerned that the top of the tank isn't flat. Its really "concave", like an anvil was sitting on top of it, caving it in.
My plan was to add a 3" hole in the top for the toilet inlet; I didn't have the manufacturer do it, because I'm not super-confident of my measurements for the toilet's final location, so my plan was to mount the tank, then mark it from the top, once the bathroom fixtures are back in place.
I'm just afraid that a hole that isn't perfectly perpendicular to the pipe isn't going to be perfectly round, and therefore, won't seal.
Anyone ever run into this? I'm thinking maybe I can put it on saw horses, flip it upside down, temporarily plug the vent fitting, and fill it with water. Maybe the weight will persuade it back to square. (?)

(fwiw, my vts grey tanks that I bought are perfectly square.).

[Protagonist]

Originally Posted by Chuck

I'm thinking maybe I can put it on saw horses, flip it upside down, temporarily plug the vent fitting, and fill it with water. Maybe the weight will persuade it back to square.

Probably won't work. Once dented, thin sheet metal is unlikely to go back to flat.

But if you really want to try it, you'll probably get the best results like this:
1 - put it on a flat surface— a concrete or hardwood floor, so the entire top of the tank is supported. On Edit - Use layers of plywood to get enough thickness so that the vent pipe has some clearance under it.
2 - Use icewater. Cold will help to shrink the metal.
3 - Drain through the vent pipe after the ice melts. Don't try to flip the tank over until it's empty.

While you're at it, make use the area around the tank is dry, so you can detect any leaks around the edges of the top of the tank.

[Chuck]

but...its plastic.

[perryg114]

Send it back and get one that is made correctly. That is a factory defect.

Perry

[Tony S]

Chuck

That sucks. I would second sending it back. I hope you can if you want. Let us know what you do. Who did you get it from?

I have read many of your posts and followed your work with much interest. When I first was looking and at the time I bought I came across your posts and pictures. You were talking about your grey thank situation back then. Good to see you are moving forward.

You have responded to a couple of my posts in the recent past. By the way, I too am from the Boston area. I grew up in Braintree. I moved away in 1978 to Oregon.

I have my 1973 Tradewind open up a bit, as in, I can see the concrete floor below. I am getting ready to order tanks too. I have to Decide if it is important to me to stay in the belly pan. I like what Minno did and Top with theirs. They are well documented with pictures.

I too am being restrained by the weather. I got my paint for the frame and now have to wait for 10 or 20 more degrees.

I will be following your posts

Tony Scolaro
Rogue River, Oregon

[Protagonist]

Originally Posted by Chuck

but...its plastic.

Clearly a senior moment on my part. I have no excuse.

[SSSabre]

Your idea of placing the tank upside down on saw horses is a good one. Plug your vent, and add some warm water. This should allow the material to relax. It may be temperature related, as the sides of all three of my gray tanks flex with temperature changes. The tanks appear to be under vacuum when cold, and under pressure when warm.

[dznf0g]

I'm with Paul, I think heating it would work. If hot water isn't enough, I would get out my salamander kerosene heater and heat the whole bottom until pliable. Then set it upside down on the saw horses and work it over with a heat gun until evenly "unsagged".

[Chuck]

Well, I contacted the re-seller (who doesn't make the tanks; they just order them, and the factory drop-ships them), sent them pics, and they forwarded them off to the manufacturer. The manufacturer said to throw it away, and we'll send you a new one. Great!

So the replacement came a couple of days ago. It has the same problem...only less pronounced.

with my level across the tank, measuring the depth of the dip...the first tank was 1.5 inches deep; the replacement is only 1" deep.

So....I took the new one outside, flipped it, and filled it with water. That makes the top sag in the other direction. Great. I just don't know if this is going to "straighten" it out, or if it'll only be that way when its upside-down and full of water. (which doesn't really help. )

I'm not looking for perfection; I just want to be able to connect the toilet to it in the intended fashion. I'm thinking that a grommet fitting might allow for the imperfection more so than a threaded fitting, which would have to be perfectly perpendicular to the riser pipe. (or toilet flange).

[SSSabre]

If you have some give in the material, you should be able to pull it up true when you mate the closet flange with the toilet. If the plastic is stiff and your concerned about stress cracking, some heat applied to the area should permit you redirect or reshape some of the deflection and relieve the stress. For the vent, you can use a flexible coupling to compensate for alignment irregularities.

I am just thinking out loud here as I can't put my hands and eyes on your install.