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Old 09-16-2006, 11:22 AM   #1
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Big Job turned into bigger JOB, need advice.

My comments are about my 1976 31ft Sovereign Intl.

This started out as a project to replace the Black water tank dump valve and as is the case much of the time, it led me to uncover a much bigger problem..... MAJOR rust damage!

When I removed the bumper and the plastic compartment that holds the sewer hose (I had to do this to get at the valve), I discovered that there had been an undetected SLOW sewer pipe or black water tank leak, at some time in the past. The leak must have been repaired at some point but the caustic contents from the leak started a rusting process that has done substantial damage to the rear part of the holding tank support pan and also the metal cross member that spans between the two main outside frame rails. This is the metal rail that is between the holding tanks and the bumper compartment where the 3" sewer pipes come through the big holes, turn and go to the sewer exit. This cross member provides the support for the rear of the tank pan (the pan is bolted to it by several bolts) this part of the pan then supports the rear weight of both holding tanks. The bottom part of this metal cross member is just about eaten away by rust and the pan is eaten away in several places, as well.

Depending on how far forward the pan has been weakened by the rust would detemine if it can be patched. However, the best and most economical solution might be to just replace the pan with a new one. I am not sure what to do about the metal cross member. That's got to be repaired/replaced but it's certainly beyond my capabilities.

Anybody had this problem before. All advice will be appreciated. Thank you, Bill

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Old 09-16-2006, 01:16 PM   #2
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I'm not sure if it bears any actual resemblance to my Argosy, but the support pan was galvanized and in pretty good condition. Fairly small angle iron cross pieces span between the main frame at front and back of the tank -- those are 75% rusted through. Haven't managed to get to it yet but will involve a trip to the welder.

Hope we can get some other experiences up here for you.


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Old 09-16-2006, 01:55 PM   #3
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Similar, but not exactly.

Bob, that sounds similar to mine, except my rusted away crossmember is about 8 inches wide, top to bottom, with a 2 inch "lip" at the top and a 1 inch "lip" at the bottom. In the base of the "lip" is where the self tapping bolts are screwed that hold the pan up. This base part is rusted away completely for about 2 feet on the curb side and another 1 foot area near the street side. Additionally, making this crossmember hard to repair, are two 4 inch circle holes cut about 2 feet in from both ends of the span. These are to allow the 3 inch sewer pipes to come through the crossmember, from the holding tanks, to exit to the streetside sewer outlet. I'm wondering if a 2 inch angle iron peice welded at the bottom of the crossmember, all the way across, would be adequate. Then it could be drilled and tapped to accept the bolts to hold up the pan. Of course the pan bolt holes would have to be relocated rearward an inch or so to match the holes in the angle iron. The angle iron would also have to be cut out about
1 1/4 inches to match the sewer pipe holes. That would weaken it somewhat, seems to me.

I'm hoping someone else has had this problem and fixed it already......and maybe even has PHOTOS!!!! Bill
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Old 09-16-2006, 04:51 PM   #4
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Here are some photos. I have cleaned and vacuumed all the loose rust pieces, so it does not LOOK as bad in the photos as it actually is. Bill
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Old 09-17-2006, 02:57 PM   #5
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Bill, I'd have a welder look at it and see what he has to offer as far as suggestions.

My .02, I don't think you need to put in a new crossmember. It seems to me that you could weld on a piece of angle to the bottom half. Not just tack welds, I mean weld a bead all the way across from one side to the other, after you cut the holes for the pipes. Another thought is that you could have a patch custom made and have it welded on ? As for the pan under the coach, I have no experience with those. I agree though that it would be a two man job to take it out and repair or replace.

Good Luck, let us know how it turns out.
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Old 09-17-2006, 07:02 PM   #6
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I have dealt with a similar problem with a fresh water tank. It was fixed with a piece of angle iron to replace the crossmember, and a piece of 5/8" marine plywood under the tank. As long as you put something on the angle iron and plywood to protect them, the repair should last for years.
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Old 09-17-2006, 07:51 PM   #7
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Thin metal

Thanks for your comments, guys.

Here is a concern that I haven't mentioned, yet. This crossmember that holds up the pan for both tanks is not very thick, even when it was new, maybe 1/8 inch. And it is completely eaten away by rust in some places along the bottom, meaning that the "L" lip on the bottom where the pan is supposed to be bolted for support, is gone! Notice that in the bottom right photo the missing "L" and the pimples in the silver paint - those pimples are heavy rust under there. On the far right side there is about 4 inches, top to bottom, of the crossmember rusted away, it's gone, and the pan also has a long hole in it under that area of the crossmember, as well. Also there is rust across the back of the crossmember that I cannot see. I know it's there because big chunks of it fell out when I tapped on the crossmember.

According to my service manual, this galvanized pan, which is bolted to a frame member on all 4 sides, supports the weight of both holding tanks, the styrofoam pads and the slope pads. It all sits right in that big pan. Apparently there are no straps or anything holding the tanks up there. When you remove it, you must support both tanks with something to keep from damaging them and/or the connected plumbing. It's not clear to me just how that can be accomplished. One thing is clear, once you get the pan down, you are forced to make ALL repairs sitting right there. Welding, new pan, etc. The trailer cannot be moved without completely disconnecting all plumbing, vents, etc. and dropping the tanks. Then you can move it.

So, any ideas? Bill
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Old 09-17-2006, 08:06 PM   #8
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Bill, yours and mine are a bit different, but some things are the same. The steel cross member you are taking about is different on mine. Mine is horizontal where yours is vertical. The pan you are speaking of (on the ’73) is held in place (riveted in place to a) by a couple of L-shaped pieces of steel that run laterally in the frame.

Let me tell you, removing all of this stuff is a yucky mess. Make sure the tanks are as empty as possible, remove the plumbing lines and go to work. Like others have said, the best idea is to remove it all then evaluate. You will probably need a new pan (Uwe gave you some great advice on how to replace it). It would probably not be a good idea to tow the trailer “down the road” to a welder, but see if you can get somebody to come out to the trailer and replace that cross-member. Another option is to cut that member in half laterally and bolt in a new piece. Difficult to do and may interfere with other stuff back there. But may be workable.


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Old 09-18-2006, 09:43 AM   #9
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I gutted my '73 Sovereign 31' to the plywood floor.(see my recent post)
Removed the toilet and flooring below.
What a mess!!
I suspect that your photos depict only the very tip of a much larger iceberg.
Those storage compartments in the bumper are, in my opinion, poorly designed.They create a significant water problem by allowing rainwater to puddle inside the underbody against the frame. Mine has been removed.
Regardless of your chosen repair method, try to address the cause of the problem too.
When I remodel my bathroom I'm going to include an easy access hatch to the tank below.
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Old 11-15-2006, 06:57 PM   #10
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Bill, I had the same problem with my 76 Sovereign Intl. I had to replace the rear bulkhead, as almost the bottom lip was rusted away. While I was at it I had a new pan made that allows me to get to the valves and piping without having to drop the whole pan. I've attached some images of what I had built. I hope they will be helpful.
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Old 11-16-2006, 05:28 AM   #11
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More to the story

Hey Bear, great photos!

There is much more to this story than was covered in the thread you read, including more photos that shows what I did. See this link:

I cut two access doors in my refurbished pan to provide easier access to the two sewer gate valves. The fact that the 3" sewer pipes are "glued" to the gate valves makes it un-nescesserily difficult to replace a defective valve. You have to cut the elbow loose from the valve to get the valve out! Then you have to replace the elbow, as well, and re-splice it into the line. NOT a good design!!

I'm very curious what you paid for your total repair, including the metal work, if you don't mind telling me. I have limited places to get work done here in this small town, so I chose the approach of refurbishing my original pan because I was fearful of ever getting one made locally that would fit. The original one was hard enough to get back up there. Bill

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