Forum Discussion

wmcreid's avatar
wmcreid
Explorer
Jan 29, 2015

Black Tank Leak - questions

We have a 2003 Keystone Sprinter 5th wheel. The black holding tank had a repaired crack (8" long across bottom corner behind the valve). After approximately one year of use the repair began to drip and then pour. I plugged it with epoxy putty which lasted about a month, more epoxy - another month, and then a big gloopy gob of epoxy putty, gorilla glue, and space-age polymer ceramic that I found at a hardware store in Texas. After about a month the whole patch fell off into the dirt under my trailer and floated away in a river of yuck. We let the tank dry for nearly a month and I scraped and sanded everything along and around the area of the crack. I let it dry a couple of more days, sanded it some more and then I covered the whole corner area of the tank with loctite heavy duty epoxy resin and two layers of glass cloth. I let this dry for nearly a week. This patch worked perfectly. It was actually easier to accomplish than everything else I had done up to that point and I can honestly say that the epoxy and glass cloth is a sure cure if done properly. Unfortunately, two months after my sucessful repair I noticed liquid dripping from that area again. Once again we let the tank dry for a month and I climbed under there to inspect. The patch is solidly in place still and there are no apparent leaks anywhere around the tank. I've felt along the top of the tank flange where I can squeeze my fingers in, but I can detect nothing. The repair is solid, the tank is not leaking anywhere that I can see, and the drain lines and valve connections look good. I am at a loss here. I don't think it's possible to overflow one of things, and I think if that were the case there would be some indication visable, like the water rising in the toilet or something. Anybody got an idea here?
  • Endricken's avatar
    Endricken
    Explorer
    May 01, 2015
    I too recommend Plasti-Mend as I've used it on both the gray and black tank leaks due to splits/cracks in the ABS from mistaken tank overfilling...Both repairs are still holding almost 2 years later.
  • wmcreid's avatar
    wmcreid
    Explorer
    Apr 30, 2015
    It has been four months since I fixed my black water tank with epoxy and glass cloth and the patch is still holding strong. This was the quickest, cheapest and easiest possible way to get the job done and I can't argue with success. I can appreciate the debate over different techniques, but the evidence in front of me is hard to discount.
  • wmcreid's avatar
    wmcreid
    Explorer
    Feb 01, 2015
    For the sake of clarification, the original damage to the tank was done by the previous owner backing up over a concrete planter box. The leak was severe. It was approximately 8 to 10 inches long and around 3/4 of an inch wide in one area where a piece of the plastic fell out. Eventually, I repaired the crack with two layers of glass cloth soaked in epoxy resin. I scraped everything clean for three inches all the way around and really roughed up the surface with 36 grit sanding cloth before the repair. In the two months since this repair we have been through temperatures as low as 18 degrees and as high as 90 degreeS with no problems. I've filled the tank to capacity at least five times just to make sure the patch was holding. I feel pretty secure with the repair and I honestly doubt that it could have been accomplished any better given the circumstances. We live in this trailer full time and don't have the luxury of time or the equipment necessary to drop the tank for welding, let alone to redesign the tank's suspension.
    The secondary leak did not come from the repaired area and there are no other indications of any leakage. The secondary leak amounted to about a gallon of nearly clear water and it came from above the plastic tank, not the tank itself. In the last five weeks the problem has not been repeated.
    It may have been a backup into vent line or just something caused by all of the rain lately, but it hasn't happened again and I am not inclined to look for problems that cease to be problems. I appreciate all of the good ideas and advice that has been offered here, but for the time being I think I will walk over to the lake and do some fishing. Thank you.
  • Showme_5vr's avatar
    Showme_5vr
    Explorer
    Feb 01, 2015
    Yes you can fill it too full, and on some units it will leak around the vent pipe connection to the black tank. Don't ask me how I know.
  • time2roll's avatar
    time2roll
    Nomad
    Jan 31, 2015
    You don't drain the tank and let it dry to find a leak. Fill it back up then check for a few days.

    +1 for Plasti-Mend. Guaranteed permanent repair for black abs tanks. You would again need to remove existing patch. Also get a sheet of ~1/16" abs to seal over the break with Plasti-Mend.
  • shovelhead86's avatar
    shovelhead86
    Explorer
    Jan 31, 2015
    Ditto on using the product called Plasti-Mend. It is fabulous. I tried several products and finally used Plati-Mend and It is working great. i did put and additional 2X2 wood crossmember from farm to frame to help support the tank. It flexed considerably when full.
  • shovelhead86's avatar
    shovelhead86
    Explorer
    Jan 31, 2015
    NMDriver wrote:
    I guess you have filled the tank with clear water past the level of your repair and tried to find the leak. You can use red kool-aid or food dye in the water to help find the problem. Fill in stages and try using toilet tissue as a moisture indicator around your repair and other seams.

    I suspect your repair is leaking, but I would be trying to figure out what structurally is wrong with the black tank support that is breaking the tank. There is no pressure in the tank so it is likely to be related to the weight of the tank and how it is supported.

    I guess you have a plastic and not a fiberglass tank? If fiberglass then Kitty Hair should fix it for around $60 per can.

    Good luck and although I have never used one, there are plastic welders out there.
  • wmcreid's avatar
    wmcreid
    Explorer
    Jan 30, 2015
    I never considered the vent stack connection, but that's a good idea. I think that line runs up the wall behind the shower stall and there is an access panel that might let me see what is goinig on.
    I considered using a thermoplastic welder originally, but the corner wall of the tank didn't appear to be that thick and I would be working upside down. Besides that I've welded plastics before in the power plant but that was a real long time back. The glass cloth and epoxy worked well. I didn't have to buy any more tools and it was certainly easier on my back than welding would be.
    At any rate, thanks for the ideas.
  • ScottG's avatar
    ScottG
    Nomad
    Jan 30, 2015
    I wonder if you have a leak where the vent stack attaches to the top of it and driving down the road causes it to slosh and drip.
  • Ed9824v's avatar
    Ed9824v
    Explorer
    Jan 30, 2015
    geotex1 wrote:
    Ed9824v wrote:
    EMD_DRIVER wrote:
    I had a severe black tank leak, on a travel trailer that we used to have. Instead of buying a kit, I went to Lowes and bought a can of ABS cement and a short piece of ABS pipe. I used a reciprocating saw to make several cuts along the piece of pipe. I gathered all the cuttings and put them in an old cup. I poured some of the ABS cement in with the trimmings and stirred it up. I had already cleaned the crack as best as I could and scuffed the area around it with a wire brush. I put a couple pairs of disposable gloves on and spread my weld in and along the crack. That was 5 years ago and that tank has not leaked since.


    this maybe the answer if it is ABS tank, I do read that some of the newer tanks may be polyethylene this procedure will not work with this cement mix. my freshwater(polyethylene) tank leaked and I paid someone to fix it with some type of adhesive, it lasted 1 year. then leaked, I took it out again and welded it up, I took an old big solder iron from my dad and silver soldered a stainless steel disc to the bottom and welded up the tank and it has been good for a couple of years now and has about 118 gallon of water in it right now. I now have fixed other plastic items and will melt in metal screen door wire for extra support. I have gotten pretty good at it not so pretty but strong.


    Polyethylene tanks are cake to repair! As you found, it is a thermoplastic. Proper welding is to use an extrusion welder with filler rod. You'd be surprised how easy it is to find someone that can do this for you! Your method works, but you are locally thinning and altering the properties of the polymer a bit.


    When I checked for a repair shop in los angeles there WAS one and they moved out of state, I do have a hot air electric heat welder that you feed the rod into that I found hard to control, I purchased poly rods as filler and built up the area and what I did not mention, I also added a lot of extra support under the tank.

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