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?
  • BillB3857's avatar
    BillB3857
    Explorer
    Jan 30, 2015
    I had a leak where the exit fitting spin weld partially failed on my black tank. My fix was to go to the hardware store and buy a can of ABS joint cement and a small package of fiber glass fabric. After cleaning the area with acetone on a rag, coat the area with joint cement and while still wet, embed the fiber glass fabric. Allow to dry, repeat at least two more times, then overcoat with the ABS joint cement. I found, by research, that the joint cement is nothing more than ABS plastic dissolved in acetone so the repair is actually adding, not only additional ABS, but adding fiber glass reinforcement to the area.
  • geotex1's avatar
    geotex1
    Explorer
    Jan 30, 2015
    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.
  • Ed9824v's avatar
    Ed9824v
    Explorer
    Jan 30, 2015
    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.
  • Snowman9000's avatar
    Snowman9000
    Explorer
    Jan 30, 2015
    The Plasti-Mend stuff is excellent for repairing ABS waste piping and tanks.
  • EMD_DRIVER's avatar
    EMD_DRIVER
    Explorer
    Jan 30, 2015
    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.
  • geotex1's avatar
    geotex1
    Explorer
    Jan 30, 2015
    Honestly, all the time and effort and materials put into repairing you could have replaced the tank. ABS is repaired by solvent welding a patch panel. Don't bother with anything else as it will not last because it won't fuse, just adhere for a time. However, aged and chemically contaminated ABS does not weld so well I would suggest as others and do a staged clean water test. If your patch is the culprit, consider a new tank.
  • agesilaus's avatar
    agesilaus
    Explorer III
    Jan 30, 2015
    I would certainly try that ABS repair kit before trying plastic welding. Here is a clickable link:

    Amazon
  • ed6713's avatar
    ed6713
    Explorer
    Jan 30, 2015
    http://www.amazon.com/Plasti-Mend-Plastic-Repair-Holding-Tank/dp/B003JC3UB2/ref=sr_1_5?ie=UTF8&qid=1422580636&sr=8-5&keywords=rv+tank+repair+kit

    Might try this.
    EternaBond is also commonly used to repair waste tanks.

    http://www.eternabond.com/AlumiBond-p/rv-as.htm
  • NMDriver's avatar
    NMDriver
    Explorer
    Jan 30, 2015
    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.
  • agesilaus's avatar
    agesilaus
    Explorer III
    Jan 29, 2015
    I've heard here that you can find people who will "plastic weld" the crack for a permanent fix. Or you can buy the welder (Harbor Freight has them) and try the fix yourself.

    Wiki


    Harbor Freight Tool

    As usual with HF: buyer beware.

    And a Video:

    YouTube

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