Visit our Popular Forums

mharrison@ie · 04-11-2007, 06:27 PM

I am replacing the rotted wooden floor, and I am stripping off the aluminum underbelly at the rear as well.

When I got the underbelly off, a whole slew of rust fell out, as well as some styrofoam sheets. The holding tank is hanging in the air supported by the plumbing connections.

I can see which cross members I need to replace, but I cannot see how the black water holding tank was supported. I do see the remains of some sort of a steel tray which presumably supprted the styrofoam base under the holding tank. But how is the steel tray supported?

Anyone know?

Thanks.

Mike

TomW · 04-12-2007, 03:29 AM

Originally, the slew of rust was a galvanized metal box. The box was supported by two lengths of angle iron that stretched between the frame's C-channels.

Hopefully, the styrofoam pieces that fell out are reusable. If not, take care that your replacement pieces allow ducted air from the furnace to circulate.

Tom

mharrison@ie · 04-12-2007, 07:32 AM

Tom:

Thanks for your reply. I guess that one of the transverse supports for the galvanized box is the one right at the back of the coach, immediately below the access hatch. And lips at the top of the box just rested on the supports.

The styrofoam is re-useable, but I am not sure how deep the original galvanized box was (the top is intact on three sides, but the bottom has rusted out. Can you give me a height dimension? Or tell me how the height of the top of the holding tank should compare with the top of the galvanized box?

Thanks again.

Mike

59er · 04-12-2007, 08:15 AM

Hi Tom and Mike,

was there styrofoam on top of your tank as well? I'm not sure of the original configuration of mine. when I got it, someone had already modded it. no styro and only the upper rim of the galvanized box!

tom, your picture showing the extra angle iron pieces helped me understand why those "c" channels are hung under the frame rails. thanks.

and finally, I'm assuming that once everything is back in place and buttoned up, that the belly pan covers everything? i.e. the tank doesn't protrude down below the belly pan?

sequoiacoast · 04-12-2007, 09:07 AM

My galvanized box was in sad shape as well- as you can see from the picture. I had a new one made from the dimensions of the old one. Basically the box is wider and longer than the tank itself (so you can move it around slightly when positioning your toilet). The height should be the measurement from your cross "L" piece, up to the bottom of the sub-floor (no gap).

And as Tom said, the heater feeds into it as well.

(The belly does hide the box when all done.)

FreshAir · 04-12-2007, 09:14 AM

Quote:

Originally Posted by mharrison@ie

Tom:

Thanks for your reply. I guess that one of the transverse supports for the galvanized box is the one right at the back of the coach, immediately below the access hatch. And lips at the top of the box just rested on the supports.

The styrofoam is re-useable, but I am not sure how deep the original galvanized box was (the top is intact on three sides, but the bottom has rusted out. Can you give me a height dimension? Or tell me how the height of the top of the holding tank should compare with the top of the galvanized box?

Thanks again.

Mike

I just completed replacing my b-tank. I 'm sure your's is similar to mine. I took photos of my process...including floor replacement. I have to dig the photos from my digital camera and size them to transfer them to this post. Hang on... I will do this today. My tank pan was in perfect condition but I'm not sure if I have it's dimensions. However that may not be an issue as an inch here or there may not be critical. I got my new tank from Inland Rv. Andy, the owner was very helpfull so give him a call. The styrofoam was used to create a 'pad' for the tank. I just went to my Home Depot and got 2 1/2" thick insulation styrofoam to replace the foam I had.

Neil and Lynn.

TomW · 04-12-2007, 03:49 PM

Quote:

Originally Posted by mharrison@ie

... I guess that one of the transverse supports for the galvanized box is the one right at the back of the coach, immediately below the access hatch. And lips at the top of the box just rested on the supports.

The styrofoam is re-useable, but I am not sure how deep the original galvanized box was (the top is intact on three sides, but the bottom has rusted out. Can you give me a height dimension? Or tell me how the height of the top of the holding tank should compare with the top of the galvanized box?

Mike,

The box in my Overlander is supported soley on the bottom by the two pieces of angle iron. The top of the box does nothing more than rest against the decking - there are no supports there.

The top of the black tank is flush with the top of the box. In other words, the top of the tank rests against the bottom of the decking.

The overall height of my box is 6-5/8 inches. Subtract out the thickness of 20 gauge galvanized metal (maybe a 1/16th?) and you will arrive at depth.

I have more pictures of my new box. Send me an email & I will send them to you.

Tom

TomW · 04-12-2007, 04:00 PM

Quote:

Originally Posted by 59er

... was there styrofoam on top of your tank as well?

... and finally, I'm assuming that once everything is back in place and buttoned up, that the belly pan covers everything? i.e. the tank doesn't protrude down below the belly pan?

No styrofoam on the top - the tank rested against the decking.

The belly skin does cover everything, but since the tank hangs lower than the main frame (but is protected by angle iron welded to the frame), the belly skin transitions to cover it. I've heard that, on newer model Airstreams, the belly skin stops at the galvanized box. That would be a good idea because I think my original galvanized box's demise was partly due to dissimilar metal corrosion caused by laying the aluminum belly skin against the iron box.

Tom

Ganglin · 04-12-2007, 05:19 PM

If it helps any. The 72 service manual shows the styrofoam as 1 1/4 thick by 22 1/2 by 48. None on the top as stated above. On each side of the tank a piece of 1x1x7 styrofoam to keep it centered. The styrofoam was held in place by double sided foam tape. Everything held up by 2 pieces of angle iron. Ours was redone at some point - they reused the tray - but replaced the angle iron with aluminum.

FreshAir · 04-12-2007, 08:01 PM

My tank tray was not supported by angle irons on the bottom. It is bolted down from the floor and into the lip that surrounds the tray as my photos show. If this is original I do not know as it is evident it was removed by a PO to patch the floor. Hopefully my photos are self explanatory. Please PM me if you need more views or have questions. Oh, yes another thing. I think my tray is not original as the heater duct entry is non-existant. My heat is now wall and portable so my duct is inoperable. Unless you get snow regularly in Florida it may not be a concern to you either.
Neil and Lynn

FreshAir · 04-12-2007, 08:30 PM

I noticed that it was indicated that styrofoam 'bumpers' were inserted on the sides to keep the tank centered. By the time my tank was bolted by the toilet flange, the sewer connections at the collector and the dump valve exit was secured the tank was not moving any where. Here are a couple more photos that did not make it into my first post.
Neil and Lynn

FreshAir · 04-12-2007, 08:38 PM

This photo did not 'take' on my last post.
Neil

59er · 04-13-2007, 09:02 AM

Neil (or anyone),

From the pictures I can tell that you sub-floored the entire rear and then cut out the holes for vents, toilet, etc.

that's what I'm in the middle of now and wondered if you are adding anything to support the toilet mounting flange or will it drop in from the top?

Mine is already glued into the tank (original) and if I make the hole large enough to fit the flange up through, then it can't be supported by the sub-floor?

I know originally, there was not much of the sub-floor in that area because they cut a huge opening... and I'm guessing the toilet basically sat on a plank that spanned the opening? I'd like to leave as much sub-floor back there as possible...

Looking for suggestions?

mharrison@ie · 04-14-2007, 09:09 AM

Doug:

I think you need to cut a hole in the floor about 4 1/2" dia. over the input to the Black water holding tank (but be careful -- see below). You should have a toilet mounting ring (black plastic in my case) that fits into the hole you just cut, and which has an external thread on its underside. This screws into the tank inlet fitting. It will support that part of the holding tank. The mounting ring also has slots to accept the wc stool.

The 4 1/2" diameter hole must be directly over the hole in the holding tank. In my case, the previous installer had made the hole closer to 5 1/2" dia. to allow some flexibility in installation. However this serves not only to weaken the floor unnecessarily, but also to make the support area for the wc stool much smaller, so it has a tendency to move about when it is being sat upon. Some people find this unnerving so I will try to get my location as precise as possible.

Mike

FreshAir · 04-14-2007, 10:11 AM

Doug, Mike; Here are photos of mine taken after I removed the toilet and as I replaced it. You probably see the same thing that you saw with yours, Doug. My PO had also glued the floor flange (if you look closely you may see the outline that the removed flange left) to the tank. However in my case it came off easily. Since I was replacing my tank as well as my floor my new flange (second photo) screwed to the tank and makes a very secure anchor for the toilet. A side note: I coated all of my new floor plywood with fiberglas resin....both sides and edges. I figure that this area will always be prone to water leaks and spills and I don't want to do this again. I have built 4 darkroom PLYWOOD sinks in 30 years and coated them with F.B. resin and have never a leak. Glad to provide more help.

Neil.