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Mike 08-18-2002 08:53 AM

Replacing Metal Box for holding tank
Hello and help!

Just bought a lovely 1970 International Land Yacht but the holding box for the black water tank rusted out completely. We removed the box leaving the tank intact and dangling of course. How difficult would it be to replace the box or I wonder if there is a more modern method to secure the tank. Thanks.

74Argosy24MH 08-18-2002 09:27 AM

Any decent local welder should be able to make a new one, give him the old one for a pattern.


Mike 08-18-2002 10:49 AM


Thanks, I'll check around. What do you think would cause that entire box to rot out?

74Argosy24MH 08-18-2002 12:32 PM

It is over 30 years old, maybe it just failed, but I would check and see if you have a leak somewhere. If it gets wet, it probably would take forever to dry out. I have drilled several 1/8" holes in different pans, tubes, etc. where I have found water. Have no idea how it got there, but figured it was better to let it drain than stay.


j54mark 08-18-2002 08:51 PM

I had the same problem on my '85. Fortunately, I was able to find a salvage unit. However, I did give some thought to what I would do if necessary to fabricate one.

Mine was made of plain steel sheet metal, painted. With all the aluminum they have handy, I wonder why Airstream did not use aluminum? Unless someone knows a good reason why, I believe I would get a sheet metal shop to rivet one together out of galvanized metal.

Also, there is rather a good deal of insulation (principally styrofoam) used in those pans. Do not forget to add that when you re-assemble.


Mike 08-18-2002 10:13 PM

Thanks for the tip. What caused your box to rot? Also, the floor in the sink area of the bathroom is also rotting so whatever caused that problem ended up in that box.

74Argosy24MH 08-19-2002 05:36 AM

With all the aluminum they have handy, I wonder why Airstream did not use aluminum?

$, $, and $. Steel is dirt cheap compared to aluminum. Structurally there is no reason not to use aluminum. If I had to replace mine, it would be with aluminum.


Mike 08-19-2002 06:58 AM

good question John. That old box was so rotted out I don't know how anyone can reconstruct it. BTW This morning I poured a gallon of water down the toilet and water started dripping (shortly thereafter) by the cap out of the holding tank.. Could this slow constant drip have caused all of that damage (over years?).

74Argosy24MH 08-19-2002 07:36 AM

If you are talking about the cap on the end of the pipe where you hook the hose to dump, I don't think that would be it. If it is that cap your dump valve is leaking. It is a gate valve, could be something as simple as some crud keeping the valve from closing completely.

I would think more like a leak between the toilet and flange. How is the floor? It could have been from the sink if the floor is rotten beneath it. Dump some water down it and see what happens. Water can do some weird things. As long as the tank is dangling, give it some time and keep watching. Even if it goes in just a few drops at a time, it probably will never come out until it rusts through.

If you don't find an obvious leak, that might not be suprising either. If the metal is completely gone, it could have been defective from the start. It seems like a leak would have caused it to rust out in an area on the bottom, then drain. It would continue to rust because of the moisture, but it does not seem like anything but the bottom would be really bad. Sort of like the floor on an old car will rot out, but further up it will not be as bad.

All they really need to make a box is the dimensions. You might have a harder time getting it to a shop in one piece than they would making a new one.


Mike 08-20-2002 05:27 AM

bad box
Hey John,

Here's a scary thought. This trailer sat 50 yards from a creek. The folding step under the door was totally re-putted and I'm now wondering if water came up under the trailer however, the bathroom floor is rotted right below the sink. I did put water through and didn't see anything but I'll try again. The wood right inside the rear battery storage area is rotted also and aside from rain getting in I don't know how that could happen. The wood from the bathroom forward is excellent so that may rule out the flood theory.

Also, about that box. Someone said I should use aluminum instead of steel but Imwondering if steel was used because of the weight?


74Argosy24MH 08-20-2002 07:20 AM

Not really knowing the area I wouldn't hazard a guess on the trailer flooding. If the rest of the floor is OK the bathroom floor is probably 'normal' damage. Some people maintain, others get to it. Things like trailers that are not used but a few times a year often go to the bottom of the list. It might have leaked for years until the floor began to get weak or it changed hands.

I would personally use aluminum to replace the box, but I work with it alot. It really is about 3 or 4 times as expensive as steel to buy and I would hate to insist that it is the only way to go. The steel box on most trailers is still going strong after all these years. My best advice would be use steel, make sure you have a really clean surface for paint, and check carefully again for leaks as you reassemble. It should last longer than the trailer.


tod47d 10-26-2002 04:40 AM

angle iron for box supports
Before ya'll run out and buy new angle iron for tank support cross members(mine were rotted) check around for an old bed frame. The angle iron appears to be identical to original and its a good way to recycle steel.

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