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Old 05-04-2019, 07:05 AM   #1
goodellj
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Kitchen Gray Tank Leak and Repair

I recently repaired a kitchen gray tank leak in my 2012 Montana 3150RL. I had a heck of a time finding the leak. It was apparently on an upper part of this 40 gallon tank because it only leaked when the tank was pretty full, near the drain. This tank is about 5’ x 2’ x 10”D, and runs side to side right above the dual axles with the drain on the left side of the camper. We spent the winter in Arizona so I decided to fill the tank and look for the leak because this would be a good place to dry it out afterwards. I filled the tank and I cut a flap at the drain to look for the leak. It was on the opposite side from where I thought! Water dribbles down to the low point near the drain (left front) when the tank is pretty full, and I found that the water was following the bottom of the tank to the low point (duh!). When I got a light into the belly and stuck my head in, I could see the water was leaking from somewhere near the front right corner.

I drained the tank and cut another flap (gulp!) on the opposite side and looked for the leak. I never would have found it if I didn’t know exactly where it was. This hairline crack is very hard to see, but when the tank is near full it must flex and the crack opens up. I found lots of useful info online on fixing it, and the best and most helpful were Ray Burr at “Love Your RV” https://www.loveyourrv.com/repairing...h-plasti-mend/ and Bob ‘Montana Master’ Rohrman in the 5th entry of this thread http://www.montanaowners.com/forums/...ad.php?t=72308 . My hairline crack was just like the ones that Ray experienced and in a similar position.

I decided to use Plasti-Mend since Ray and Bob both recommended it. I wanted to provide some support under the tank like Bob did because it seemed logical and Bob said the repair was successful with no recurrence, although Ray disagreed with the idea of altering the tank support design when I asked him by email. Planning and prepping this took more time than the actual patch, but I abandoned the idea because it was just too hard to do without dropping the entire Coroplast belly under the tank. I did the repair just as Ray did, and I had to unbolt a tank support beam to move it out of the way just like Ray. Everything went back together just fine when I reassembled it, although putting the beam back in place was physically hard because of the limited access.

Plasti-Mend is a serious product and I was very impressed with it. It costs more than the alternatives available at hardware stores, but I think it produces a much more sturdy and robust patch. It requires respiratory protection against organic solvent fumes, and I recommend eye protection also because I did the work while looking straight up. I used it exactly according to the directions, which I read many times. The patch for a crack is brushed on with mesh reinforcement, and the instructions say to go several inches beyond the crack, which was why I had to move aside the tank support beam even though the crack did not go under it. The patch is supposed to be stronger than the original tank wall.

When I closed up the Coroplast I used black Gorilla Tape “Tough & Wide” 2.88 inches wide, which was way better than some other Gorilla Tape that I had in my toolbox because it is extra wide. I also added another cross-beam directly below the tank, under the Coroplast. The Coroplast there was drooping a little because it had held the water leakage and also it is about 8 feet between cross-beams, so it seemed like Keystone should have put one there originally.

While I was underneath the camper I replaced most of the Tek screws holding the Coroplast up, using stainless steel screws and fender washers. Almost all of the screws in the front half of the camp came out after I loosened them with a ratchet wrench, but the screws in the rear half (from the axles backwards) all broke and had to be re-drilled. This replacement is a project, since there are about 100 screws total. In the back half of the camper I stopped trying to remove them and just drilled a replacement adjacent to any screw where the Coroplast seemed a little loose. In the rear of the camper there are some screws holding some sheet metal along with the Coroplast, which were loose and I re-drilled replacements.

I’ll test my gray tank repair next time we go camping and have hookups. I am crossing my fingers! Wish me luck!
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Old 05-04-2019, 07:18 AM   #2
goodellj
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Here is a picture of the crack with arrows pointing to the beginning and end of the crack. You need a bright light, good eyes, and it helps a lot to know what you are looking for.
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Old 05-04-2019, 10:27 AM   #3
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I see nothing so you must have done a good job.
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Old 05-04-2019, 01:40 PM   #4
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Ha Ha Ha and Ha!
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Old 05-05-2019, 09:22 AM   #5
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The tank looks like a two piece tank. Keystone hangs these tanks in a manner not prescribed by the tank manufacturer. More than likely the tank will fail along the two sections in time. You may want to check the other tanks for their construction. The fix is one piece tanks, properly supported.
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Old 05-05-2019, 10:38 AM   #6
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Thank you for posting the details and pictures. I'm a visual learner and this level of detail and pics really helps me. I don't have a problem "now" but I like to keep a resource for future could happens.
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Old 05-05-2019, 01:05 PM   #7
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There is a sticker on the tank that says it is an "Ameri-Kart HT541", and according to the company documents I found on the internet it is installed exactly as the manufacturer recommends. It is a one-piece vacuum-formed ABS 40 gallon tank.
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Old 05-05-2019, 03:25 PM   #8
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A vacuum formed tank is a two piece tank. The top is flat and glued/welded to the bottom vacuum formed bottom. Keystone is not mounting these according to the instructions, and the "engineer" I spoke with at Ameri Kart. The instructions you are seeing online speak to several ways to mount the tanks. The chassis mounting method is not being used. Keystone is hanging the vacuum molded tanks on rails with no straps.

The rotational formed tanks are designed to be hung on rails as the tanks have a flange an inch or two wide which is suitable, not needing straps or other support from below. (Although extra support is good)

It is odd that their instructions say: To test tank,fill with plain water and check visually. Do not use liquid soap or DETERGENT SOLUTION as the solution will cause stress cracking in the plastic.
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Old 08-04-2019, 05:06 PM   #9
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So far, so good. My repair is holding up! Before I put the camper away for the winter I will do a complete full up of this tank, open the coroplast belly, and look for leaks before emptying.
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Old 10-26-2020, 07:36 AM   #10
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Gray Tank Repair Failure

My gray tank patch failed. I noticed some leakage from the coroplast underbelly through some small drain holes that I made 2 years ago. When I got home I opened it up and saw the same crack right in the middle of my Plasti-Mend patch, only bigger.

I repatched the crack with Plasti-Mend, and I was more aggressive this time with a patch that covers a bigger area and incorporated more fabric.

I also contacted Ray Burr at "Love your RV" to see how his patch held up. He said his repair leaked again and he repatched the same crack every few months. After about 3 times he switched to a product called G/Flex Epoxy and there has been no leak now for 22 months. I would call that a better success than Plasti-Mend.

If my leaks reoccurs, I intend to use G/flex next time. Stay tuned.
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Old 10-31-2020, 07:30 AM   #11
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I would get it nice and clean and try some Eturnabond tape on it. It sticks like mad and is very flexible.

Friend at work had a hole in his plastic buried sewage pump tank (you know the kind that pumps sewage up to the drain line). I gave him some Eturnabond tape years ago which he used on it, and its still holding up just fine even being under sewage water.
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Old 01-15-2021, 08:21 AM   #12
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This tank has leaked again. I was hoping the repair would hold up longer, but after trading emails with Ray Burr and LoveYourRV.com I found that mine lasted about as long his Plasti-Mend repairs did, which was about 2 or 3 months of camping. On his last repair he switched to G/flex Epoxy and it has lasted a lot longer, which for him has been about 16 months of full-timing.

So I am in the process of planning a repair of this cracked tank again. I am going to use G/flex Epoxy. Before working on this tank I never did any kind of repair like this. One recommendation that I will incorporate this time is to drill a tiny hole at both ends of the crack, which after repair will strengthen the area and prevent the crack from spreading. The G/flex Epoxy directions say to cut a "channel" along the crack, which I will do with a Dremel tool. This will allow the epoxy better access to the crack. I will make sure I do not go too deep. They recommend roughing up the area with 80 grit sandpaper, cleaning with alcohol, and thorough drying. The G/flex directions also recommend a "flame treatment" as a final preparatory step, in which a torch flame is quickly run along the crack about a foot per second. There will be no visible change in the plastic, but the surface will be oxidized and the epoxy will adhere better. I want this to work so I will do all of these steps.

When I examined the leak I found that the tank had cracked right through my Plasti-Mend repair and was even longer than before. Wish me luck!
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Old 01-15-2021, 08:41 AM   #13
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John,

I recommend pulling your credit card out and ordering a new tank.
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Old 01-15-2021, 08:43 AM   #14
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Eventually you will have to replace the tank. The question is how many repairs you will do before you come to that conclusion. I tried repairing my grey tank, and when it failed the third time, I replaced it. A few years later, my black tank failed, and I immediately replaced it. At that time, I installed strapping to support the bottom of both tanks. They can no longer flex when full, thus (hopefully), they will never fail again. My grey tank failed at the outlet flange. The black tank failed just like yours.
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Old 01-15-2021, 09:36 AM   #15
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I may eventually conclude that a new tank is needed. Can you provide some info on the make and model of the replacement tank? Was it a direct replacement, like the OEM tank? How much did it cost for the tank and for the complete repair?

I have to admit that while I was under the camper looking at the crack I also was looking around at the surrounding area and thinking about what a replacement would entail, in terms of both work and cost.
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Old 01-15-2021, 10:19 AM   #16
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Originally Posted by goodellj View Post
I may eventually conclude that a new tank is needed. Can you provide some info on the make and model of the replacement tank? Was it a direct replacement, like the OEM tank? How much did it cost for the tank and for the complete repair?

I have to admit that while I was under the camper looking at the crack I also was looking around at the surrounding area and thinking about what a replacement would entail, in terms of both work and cost.
The only place I could find an exact replacement tank was from Trekwood. Including shipping it was around $500. You can find newer design one piece tanks for less, but you will have to engineer mounting solution and re-plumb which us why I chose exact replacement. There should be a white crayon number written on the side of the tank. This is the model number of the tank.

I did the install myself. If you have above average mechanical (and some plumbing) skills, you can probably do it yourself.

Attachment shows strapping supporting the bottom of the tank.
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Old 01-15-2021, 02:02 PM   #17
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Originally Posted by Hblick48 View Post
The only place I could find an exact replacement tank was from Trekwood. Including shipping it was around $500. You can find newer design one piece tanks for less, but you will have to engineer mounting solution and re-plumb which us why I chose exact replacement. There should be a white crayon number written on the side of the tank. This is the model number of the tank.

I did the install myself. If you have above average mechanical (and some plumbing) skills, you can probably do it yourself.

Attachment shows strapping supporting the bottom of the tank.
I'm curious why you did the strapping length ways and not side ways?
Thanks!

Brad
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Old 01-15-2021, 02:25 PM   #18
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I'm curious why you did the strapping length ways and not side ways?
On my rig, the grey and black tanks are mounted under the basement floor, short ends facing left to right side by side with the drains' "Y" between them. Outside of tanks (long side) rest on side to side frame members snug against the bulkheads, no place for carriage bolts. With tanks installed, there is about 1 1/2 inches of basement floor visible on either side of the short ends of the tanks. Much easier to install.

Strapping is standard plumbers perforated strap covered with 3 layers of shrink wrap.
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Old 01-19-2021, 11:25 AM   #19
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I completed my repair 4 days ago and I have had the tank pretty full twice so far, with no leak. I did the repair just like I planned it. I also asked Ray Burr at LoveYourRV.com for advice and most of this procedure is per his recommendation.

I learned a few things on this repair. When I was carving the channel over the crack with the Dremel, I did my best but I found it was hard to follow the crack exactly because of the poor visibility, awkwardness of the angle, and the disappearance of the crack under my work. My advice would be to carve a few "dots" with the Dremel over the crack every 1/2 to 1 inch as a guide, and then proceed to make a continuous channel.

The G/flex epoxy is much easier to work with than Plasti-Mend. G/flex does not require respiratory protection and actually has little odor at all. It is thicker than Plasti-Mend and easier to work with, particularly since I was applying it while looking straight up. After mixing the 2 components the directions say it begins to harden in 45 minutes, and fully cures in 24 hours. On the first coat I used a gloved finger to spread the epoxy and force it into the crack. This was so much easier than using a tool that I only used disposable plastic knife to mix and apply the epoxy, and a gloved finger to spread each coat.

After the first coat I left it an hour, then applied a second coat and a strip of fiberglass cloth over it and some more epoxy over the cloth. The third coat went on the next day.

My Coroplast is getting a little beat up. I used extra wide Gorilla tape and a hair dryer to put it back together. Time will tell on the repair.
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Old 01-19-2021, 12:21 PM   #20
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John,

Thanks for the good writeup.

It seems the quality of the repair might be better on a tank that had been removed although removing the tank would be more work. Was this a consideration for your?
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