Patching a 1996 Grey Tank?

sander17 · 05-12-2009, 11:43 AM

Oh, what fun. I go to flush the water system after winter. Since it was just water, I was able to see what came out. First clue: styrofoam pieces.....
in the grey tank? I closed the grey valve and started filling the tank with the fresh water flushing. Everything was ok until the tank was about half full, then a waterfall under the trailer. Yikes! I pulled the access cover to the valves, and tried again. The hole is somewhere else. So the next step is to pull the belly pan in this area and find where the mice chewed their way in.

So, once I find the hole, what is the easiest way to patch it? This is a light grey plastic tank in a mid-90's Excella. I am hoping that the hole is accessible without removing the tank. I haven't tried locating the entry fitting yet. I suspect it might be under the shower.

Do you think that a fiberglass repair kit, with 2-part epoxy and fabric would stick to the plastic?

Inland RV Center, In · 05-12-2009, 11:54 AM

Quote:

Originally Posted by sander17

Oh, what fun. I go to flush the water system after winter. Since it was just water, I was able to see what came out. First clue: styrofoam pieces.....
in the grey tank? I closed the grey valve and started filling the tank with the fresh water flushing. Everything was ok until the tank was about half full, then a waterfall under the trailer. Yikes! I pulled the access cover to the valves, and tried again. The hole is somewhere else. So the next step is to pull the belly pan in this area and find where the mice chewed their way in.

So, once I find the hole, what is the easiest way to patch it? This is a light grey plastic tank in a mid-90's Excella. I am hoping that the hole is accessible without removing the tank. I haven't tried locating the entry fitting yet. I suspect it might be under the shower.

Do you think that a fiberglass repair kit, with 2-part epoxy and fabric would stick to the plastic?

Fiberglass bonds to fiberglass extreme well.

But bonding it to plastic is a very short term fix. As soon as the plastic tank flexes, it will spit off the fiberglass patch, even if you roughen the patch area.

Depending on the size and location of the hole, you can plastic weld or perhaps use hot glue, and that might work.

The first thing to do, is examine the cracked area, and go from there.

Andy

sander17 · 05-14-2009, 07:26 AM

Last night I took all the bolts off which held the galvanized steel pan up. I was surprised that the tank was held up only by the plumbing, no straps. The pan and the sheet of styrofoam support it from below. I found the hole. It was the size of a small fist, with tooth marks around the edge.

I have a couple of catalogs from local RV places, and they list a "holding tank repair kit". It is supposed to have the right adhesive and patch for this type of plastic tank.

Does anyone have experience with these kits? Are there any tricks, other than lightly sanding the surfaces? We'll pick one up today and try it tonite.

Inland RV Center, In · 05-14-2009, 08:17 AM

Quote:

Originally Posted by sander17

Last night I took all the bolts off which held the galvanized steel pan up. I was surprised that the tank was held up only by the plumbing, no straps. The pan and the sheet of styrofoam support it from below. I found the hole. It was the size of a small fist, with tooth marks around the edge.

I have a couple of catalogs from local RV places, and they list a "holding tank repair kit". It is supposed to have the right adhesive and patch for this type of plastic tank.

Does anyone have experience with these kits? Are there any tricks, other than lightly sanding the surfaces? We'll pick one up today and try it tonite.

Heat in some form, is usually necessary for a good patch.

Cold patches, usually are very short termed.

The big problem, is all the extra work you have to do, when you learn that the "'patch" failed.

Andy

ts8501 · 05-14-2009, 08:47 AM

JB Weld and Fiberglass Fabric worked for me on my SOB. Use the JB Weld to "stick" the fiberglass sheet (cut to fit) to the exterior of the tank. Then saturate the fiberglass in JB Weld. My brother has my SOB, and it is still holding up fine 5 years later. I had cracks over a foot long, and small holes. I repaired 3 separate areas on the black tank, and they are holding up fine. All materials available at Lowe's, Home Depot, or your local hardware store.

sander17 · 05-14-2009, 11:43 AM

According to the parts lady at the local Airstream dealer, the tank is made of ABS plastic. She was out of repair kits, since the service dept used them all up yesterday. She suggested getting a kit for a fuel tank at the local hardware store, since they are made of the same plastic.

If I could find a flexible sheet of ABS, I suppose I could use the normal PVC/ABS cement to attach it over the hole. Has anyone ever found flexible sheets of this stuff at the normal (HD, Lowes, TSC) big box stores?

richinny · 05-14-2009, 08:13 PM

somewhere in the last 18 months or so i seem to remember a post that someone cut a hole about the size of you 'hole' to clean out the tank. he wanted access to do a thorough job of cleaning out that nice stuff that tends to grow in there. i think it was a marine type item. it's worth looking into.

dnrtheil · 05-14-2009, 10:02 PM

Quote:

Originally Posted by sander17

According to the parts lady at the local Airstream dealer, the tank is made of ABS plastic. She was out of repair kits, since the service dept used them all up yesterday. She suggested getting a kit for a fuel tank at the local hardware store, since they are made of the same plastic.

If I could find a flexible sheet of ABS, I suppose I could use the normal PVC/ABS cement to attach it over the hole. Has anyone ever found flexible sheets of this stuff at the normal (HD, Lowes, TSC) big box stores?

See if you have an Alro Steel store near you. They also handle plastics, they might have ABS sheet in stock.

Alro Plastics - ABS

Derek

Janet's Husband · 05-14-2009, 10:49 PM

Patching tanks has always been a sore spot with me. ABS by nature is relatively brittle material and with age it gets even more brittle.
The flexing a tank goes through when traveling will cause stress cracks which continue on to leaking cracks. The stresses in the tank are amplified when you travel with the tank having water in it.
Bad thing all around.
ABS is cheap, Polyethylene and Polypropylene is more expensive but far superior in strength, flexibility and durability of a tank.
The quick cheap fix is glue the tank back together. It is a temporary fix at best. If you can find a replacement "Poly" tank do it. You will find it a better be it more expensive fix.
Take a look. RV Holding Tanks

dlb435 · 05-15-2009, 06:31 AM

Harbor Freight sells a plastic welding kit. It uses hot air to melt plastic welding rods. I used this to weld my black water tank back together on my 72 Safari. My first choice was to replace the tank, but none could be had. On a 96 the replacement tank should be available. I'd recomend getting a new tank if you plan on keeping the trailer.

sander17 · 05-15-2009, 11:17 AM

Looking at the plastic tank, it was just chewed thru by the mousies. There are no cracks, so the base material seems in pretty good shape. The problem with the fabric based fixes is the large size of the hole. We went to Tractor Supply and got a kit used for fixing stock tanks and gas tanks. It is a 3/4" diam cylinder of playdough consistency two part epoxy putty. You mix the outer with the inner material and you have 5 minutes to shape it to fit the hole. After an hour, it is supposed to be hard enough to drill and tap machine screw threads into it.
I took 3 packages and kneaded them around the edges to give a mechanical hold to the patch. It is pretty ugly, but it does not have to hold much pressure. Now that it has cured, I'm going to smear some vulkem all over it for good luck. Once that cures, I'll cover it with some aluminum sticky tape to discourage the evil mice.
Then it's put the cover back on and fill the tank with water. If it fails, I can always get a blue tank for next weekend.

sander17 · 05-19-2009, 11:24 AM

Patch repair completed. After waiting overnite for the Vulkem to finish curing, I decided to skip the aluminum tape step. The real fun started when I tried to get the galvanized belly pan back up. 4 hours later, that evil thing was back up. What a royal pain in the back! Half way thru, I got out the hydraulic jack and raised the trailer up another 2 inches on the jack stands. Even my dog got bored with my colorful language and went off to a sunny spot to take a nap.
The biggest problem was the edge next to the fresh water tank. It was very tight to the axel mounting plates, the styrofoam kept getting jammed, and the sheet metal bent slightly during disassembly.
What you really need is a grease pit to stand in while working on one of these.

We'll see this weekend how the patch holds. If it doesn't, then the fun part will be tearing the cabinets apart to reach the intake to the tank. A blue boy is looking pretty good right now......

easyride · 05-19-2009, 02:48 PM

I think I would have plugged outlet,and filled it while sitting on the ground,then if it didn`t leak,drain and reinstall.Then maybe I`m just getting lazy!! Dave

sander17 · 05-19-2009, 03:33 PM

Quote:

Originally Posted by easyride

I think I would have plugged outlet,and filled it while sitting on the ground,then if it didn`t leak,drain and reinstall.Then maybe I`m just getting lazy!! Dave

The tank never came out of the trailer. It was still attached to the intake plumbing. To get to that connection, I would have had to remove the shower. The only way to fill the tank is to reinstall the bellypan, since the tank's only structural support is the styrofoam sheet under it. There are no straps or brackets supporting the tank to the frame. I wish I had the designer under the trailer with me this weekend. They could have held up the pan while I was fighting to get the screws back in.