leaking black tank- the thing I never wanted to fix
 

Noticed a leak today from the joint where the drain pipe attaches to the black water waste tank. Seepage is coming from the TOP of the joint and i notice the weight of the pipe is forcing it to pull away a bit. When I lift the pipe a little it slows. Still- I need to fix it. I ran a search and saw that WRASCAL had repaired a similar leak with fiberglass. Someone else recommended a repair kit from rv dealer. Any other thoughts? I almost am leaning towards the fiberglass in hopes that it would provide some structural support as well as stop the leak. Any suggestions or advice are welcome.

Rick

Try JB Weld for plastics. It has a good and long reputation. You can get it at most hardware stores and it comes in various forms. Make sure it is for ABS.
Amazon.com: J-B Weld 50132 PlasticWeld Syringe - Dries Off-Wite - 25 ml: Automotive

Wrascal checking in as when I saw your post I remembered that same problem.

My repair was messy (I didn't use gloves) and gave me a headache, but it fixed it. I used multiple oversized (one on top of the other) mats specifically for the strength and it was rigid.

Last fall I tried the same repair on my Deere hood - there it didn't stick worth a darn (that time I wore gloves and escaped the headache). Not sticking would still be my concern with JB Weld.

Maybe rough it up with some sand paper and wipe with some alcohol or naptha before application would help it adhere better.

So after considering suggestion and spending hours on the web reseraching blackwater tank repair- I stopped by my local dealership/storeage/ repair facility and asked what they recommended. The manager says they use a two part product that is about 80 bucks a tube that the automotive industry used for repairing exterior plastics and adds some structural integrity. It come out of a "gun' which he said like a caulking gun. I've got the trailer at home right now- so he said if I wanted to get it prepped and then come over he'd give me the gun to back home and apply it. He did, however, suggest that the appropriate prep was to grind a groove where i was going to apply the patch. So I went back home and started contemplating grinding a 360 deg groove around the entire seam, and decided maybe it was beyond my skill set-at least on the first try. I'm not even sure which dremmel attachment I'd use. So I went back and asked what they would want to do it--- and he said it would be at least an hour or maybe two. So $100 to 200.00., as it can get complicated. I agree on the last part- but have decided i trust their experience more than mine and this not a repair I want to get half right. That tank looks like polyethelyne to me and the stuff is notorious for being difficult to bond to. So- thats what I have decided to do. I've got plenty other stuff to DYI. I hope it works. photo attached.

The tanks and Pipes aremostly ABS. I have repaired several over the years and I used fiberglass cloth and ABS cement. I get the cement at Lowes in the plumbing dept. I clean the area with MEK. Get it in the paint dept. I have used 2 to 3 layers of cloth each layer larger than the one below it. Have not had any repairs fail. The best way to prevent a lot of these cracks is to not run with your tanks with any amt of liquid in them if possible. I have also found the tank support straps loose allowing the tank to bounce, need to be snug.

Thanks, Jim

Just the weight of the pipe seems to be flexing the joint. I may want to figure a way to support that pipe once the repair is done. I've repaired ABS canoes with fiberglass- and sometimes the patch worked and sometimes not. i found it was often dependent on how much flex there was in hull where the repair was done. More flex-less success. I appreciate your experience on this- however. Still-I'm going to let these guys have a go at it. If it doesn't work i'm out a couple of bills, which isn't great, but not the end of the world, and I'd likely be able to get them to comp me a couple of months of storeage fees. I can always go back at it with my own repair if need be. It is a tricky area to get into and its more the prep work I have concerns about. I'd hate to screw it up and grind through the tank. Also , they say their experience is the material offers some structural integrity-as fiberglass would. I'll post when it is done. They cant get to it until after memorial day.

Rick

repair done
 

local guys completed repair. Used a 3m product I think- when I confirm it I will send the link. In the meantime- here are a few photos. The best thing they did was build a little brace for the dis-charge pipe. I dont know how newer trailers did it- but mine was certainly in a position where the flexing caused the joint to weaken where it goes ito the tank. This should help.

I fixed a leaking plastic boat we had using a propane torch and #2 plastic like a milk jug. You heat the repair area up until it looks glossy and then heat the piece of milk jug up and lay it on top and then heat it until it turns clear. Not so much to make it burn. Then you can add layers to make it even stronger. We had tried all kinds of epoxy and caulking but it still always leaked until we did the free milk jug repair.
My grey tank is dripping a bit at the seam so I will try it there.

I like the extra support and think I will add that to my trailer as a "preventive" measure!

I'd have never thought of "welding" new plastic over a crack. What a cool idea!

- Jack

Lots of ideas out there including plastic welders you can buy. Also- there is "chemical welding" where adding mek to gum it up then spreading on a "glop" mixture of MEK and plastic bits. The devil in the details is, always, getting the right chemicals/plastics to match. Like- milk jug plastic is usually blow molded polyethelene and, my waste tank, is abs. I' be interested which one your boat was/is. Still- a neat solution.

Here is a link for what I think they used on my repair. but I may be wrong. :)


Semi-Rigid Plastic Repair, 50 mL at National Tool Warehouse

Here is the video I watched to fix my boat.
https://www.google.com/url?sa=t&sour...t4rnVsnb0rDwBA
My boat is an 20 year old Pelican which I think is poly. I think the welding would work on work on ABS but maybe you wouldn't use #2.

I actually found another link on how to make ABS glue using acetone with some scrap ABS dissolved in it but I can't seem to past the link. It's on hackaday.

Nice video. Might try it on the end caps.:)

An update on my black water tank leak:

In another thread, I forgot which one, I thought the leak was in the black water drain valve, which I replaced, and it is now not leaking and it works smoothly. BUT - I found a couple days ago that my tank was leaking around the pipe collar as it enters the tank, at the top of the seam as was reported at the beginning of this thread. This seems a fairly common problem, and I agree with others that it is caused by the flexing of the pipe at that point against the tank wall.

The problem, as I see it, is that the tank is not particularly rigid and there is too much "give" at that seam, weakening it. I repaired my newfound leak using multiple layers of fiberglass and black ABS plastic glue just like others have done in this thread. This stuff dries to a fairly rigid state and the fiberglass adds additional strength.

I also found an ABS cleaner/glue "spray" at Home Depot that I sprayed into the crack before I applied the fiberglass/ABS glue patches, and I feel this should have reduced the seepage that was happening under the old glue joint.

I have a metal "guard" under the drain pipes and I added a metal shim to it that now contacts the drain which should help to prevent some of the up and down movement of the black (and gray) water tank drain pipes.

I'm leaving on a camping trip tomorrow so will see how this holds up. When I get back, I'll look into a more secure and permanent support for the drain pipes - something like that was shown in an earlier post in this thread.

If I come up with something that seems promising, that might work on other trailers, I'll post pictures.

- Jack

Just completed a blackwater tank repair. I used a kit from Plasti-Mend:

Plasti-Mend Black

Comes with MEK*** primer and applicator, two sheets of gauze, two brushes, a can of resin and even two small sheets of ABS. It worked very well and didn't cost much at all (38-something bucks, IIRC) . . . I would say it's not worth risking the job with home-brew products and would counsel against acetone which evaporates at the speed of light. ;)

*** actually, MEK plus additives which help the cleaning/priming process.

Jack

the support they built for my pipe has worked well even on the 4x4 roads I was on a year ago. Pretty simple, to boot. It is in the picture posted earlier in the thread.

Rick

Thanks Rick - I was thinking of that post when I brought up the subject of a pipe support.

I have to crawl back under the trailer to see what kind of framing I have above the pipe. My blackwater drain pipe is MUCH shorter than yours. There's only about 1/2" between the tank collar and the elbow, and then right away comes the valve.

I may well have to stay with an underneath support attached to the metal guard strip below the tubes. What I put in there was a temporary measure that I hope will work for tomorrow's trip.

- Jack

good evening everyone. It has been awhile since I been on the forum but I am now back at repairing my trailer. I have now discovered that the pipe has come aloose from the black tank and need to be repaired or thinking about just replacing the whole plumbling (might get expensive). but as I fix one thing I run into another.

fixing your black tank
 

Seems like enough back posts that should be a help to you. Post pictures if you need help.