Black Water Holding Tank Repairs - Fact or Gimmick?

stormbytes · Feb 22, 2012

I've got a '94 Winnebago Warrior on a Chevy chasis and just found an 8" gash in the black water holding tank. Its a horizontal gash on the side of the tank, and the area is virtually inaccessible! I can't imagine how they managed that, but anyways... I called Winnie and as most of you probably know, I'd need to take out a mortgage to get that tank replaced, not to mention the time frame involved.

The best solution I've come across so far is plastic welding. It would work, but its time consuming and might involve having to take the tank down and possibly crate/ship it to the welder. I came across a repair kit by Versachem, it's called the "Holding Tank Repair Kit" and the guy who sells it says he's used it a number of times without a hitch.

Thought I'd get a second opinion before deciding which way to go. If this is a viable option I'd love to go with it for the economy and do-it-yourself factor.

This is a 38-gal plastic tank

jc2 · Feb 22, 2012

I've not had the pleasure of having to do what your contemplating but for the price of the kit mentioned at the following link, I would at least give it a try.
http://www.pplmotorhomes.com/parts/caulks-sealants/holding-tank-repair-kit.htm

stormbytes · Feb 22, 2012

That's exactly the kit I was contemplating.

I spoke with a local/reputable welder who also does plastics. He seems very knowledgeable and came recommended by Winnebago service people. I have to send him some pictures and get a quote. He runs a mobile welding rig and so hopefully it won't be too bad, especially if I can meet up with him someplace convenient.

Will post my findings...

stormbytes · Feb 22, 2012

Here are some pics of the damage.

I sent these to the welder and hope to hear back soon with a quote. Will post to the forum and heck, if it works out (which I really hope it will!) I'll add the guy's info so others might benefit from the service.

skyking1 · Feb 22, 2012

I just placed an order not two minutes ago with this company for an airless welder, some extra rod and a piece of flat PP to modify a diesel fuel tank.
https://www.urethanesupply.com/
If you can wait I will let you know how that goes next week.

Molaker · Feb 22, 2012

Looks like you or a PO backed into something.

As for access, the hitch should just unbolt. That should give you (or your welder) plenty of room to make the repair.

stormbytes · Feb 22, 2012

skyking1 said:
I just placed an order not two minutes ago with this company for an airless welder, some extra rod and a piece of flat PP to modify a diesel fuel tank.
https://www.urethanesupply.com/
If you can wait I will let you know how that goes next week.

Hah! I was just looking at that earlier today, couldn't make heads or tails of it. If I can swing it, I'd rather have a professional do this tank weld. But I would love to hear back about how this gizmo works. It seems useful for a number of applications.

stormbytes · Feb 22, 2012

Molaker said:
As for access, the hitch should just unbolt. That should give you (or your welder) plenty of room to make the repair.

I'm hoping we can avoid that and weld it as-is. I mean, it *is* accessible from underneath and there isn't going to be any more room by removing the hitch, only the angle would change. I'm waiting to hear back from the welder. Sent him the pics earlier. The suspense.......

Bill Adams · Feb 22, 2012

I wish you the very best luck! We had a leaking fresh water tank which was welded and only survived for a few years. My split was in an area which would take much more stress than where yours is located so you might have better luck than I did. I was able to find the original manufacturer, the tank model number, have them install the exact same connections (inlet, output, sensors) and ship me the tank. The shipping cost more than the tank as it was a very large 165 gallon tank, but I was able to remove the black, grey and fresh tanks myself and re-install them in reverse order. That was about 4 years ago and I no longer have water running everywhere!

stormbytes · Feb 22, 2012

I would be *very* grateful for 'a few years' with a functional and reliable holding tank

Yes - sadly shipping is the killer as most of these tanks would have to be crated and shipped as freight. Take that with having to custom-make each tank and you're looking at an expensive proposition! I wouldn't have kicked myself as badly had it not been for that fact that I SAW the gash in the tank *before* making my offer to the seller. Note that at the time, I had no idea what I was looking at. Regardless, I'd been going through some of the service records and the lady spent an arm and a leg maintaining the thing, so I'm gonna be a sport about this....

As for replacing the tank, like you said - it's not in the worst possible spot and the welder came recommended by one of the service guys at Winnebago in Delaware. This guy comes with a very good reputation for doing good work and I'm hoping that will pay off. I mean, the guy is literally fusing plastic-to-plastic, so I'm cautiously optimistic.

Anyways... I'm rambling, you get the picture.

Jammer · Feb 22, 2012

I have tried a number of plastic repairs over the years using both epoxy and plastic welding techniques.

In general, once the plastic is cracked, stress will tend to concentrate in the cracked area, causing the repair to fail. Because of the cold weather here, we have a problem with plastic parts cracking just from exposure to cold. It's a combination of the shrinkage due to temperature and the loss of flexibility happening at the same time.

That said, I've had a few successes, and it's worth a try. The plastic welding technique, properly applied, is more reliable than the epoxy.

Another technique that can work well, especially on ABS tanks, is to solvent weld a small sheet of ABS over the repair.

stormbytes · Feb 22, 2012

The tank is actually gray in color, made of flexible polyethylene. Were it ABS I'd be worried, very worried. But with the flexible plastics (made for weather compliance) I'm a bit more optimistic, especially since the weld will be made with material of comparable density.

Sweet Hitchhiker · Feb 23, 2012

I carried a tube of "Harveys 2 part Epoxy" with my older rig. The tank had a vertical split (probably from heat and cold ) All I had to do was rough the area with a wire brush or sandpaper, cut a chunk off and thoroughly mix it then apply. 10 years and it still is holding.

stormbytes · Feb 24, 2012

Well, I heard back from the welder today. Looks like it'll run me $200 for the repair. Nothing to sneeze at (for my meager means!) but a far cry from the $800 + 3 to 4 weeks the dealer wanted to replace the tank!

I'm not done shopping around, but at least I've been able to cap the damage, and so far I'm still standing

stormbytes · Mar 17, 2012

Update **

Trying to fly solo on this repair, I did some research and it seems that nothing will bond to poly-. No solvent-based epoxies, urethanes or liquid-polymer compounds can touch the stuff.

Poly-Weld (by TAP plastics) seems to be the only game in town, and their stuff is pricey and sold in very small quantities.

I'm gonna try my hand at hot-air plastic welding and report back.

Fingers crossed.

scottydl · Mar 17, 2012

Doesn't Eternabond make a product for plumbing or tank repairs? You might want to check the "RV repair" section of their website... http://www.eternabond.com/RV-Leak-Repair-Products-s/22.htm

stormbytes · Mar 17, 2012

scottydl said:
Doesn't Eternabond make a product for plumbing or tank repairs? You might want to check the "RV repair" section of their website... http://www.eternabond.com/RV-Leak-Repair-Products-s/22.htm

Virtually all "tank repair kits" are solvent-based adhesives and useless in my case. Much like PVC/ABS, these solvents literally 'fuse' the two parts together by dissolving the plastic. Once the solvents evaporate, the plastic re-hardens and the two parts are joined.

PE/PP is designed to resist agressive solvents (gas, diesel and even acetone!) and impervious to any of these. Poly-Weld (TAP Plastics) is specifically designed for bonding of Polyethylene or Polypropylene.

-- see it here: http://www.tapplastics.com/shop/product.php?pid=435&

-- see demo video: http://www.youtube.com/watch?v=h-9yhanz5DE

Its not cheap, but $50 for (2) 1-oz tubes is a far cry from the $900+ cost of tank replacement. I had originally thought that a plastic weld would be ideal, and even got a quote. After doing quite a bit of research I'm not so sure anymore. I'm gonna go ahead and order Poly-Weld and give it a shot.

-- Stay tuned

Chet18013 · Mar 17, 2012

I'd definitely use a plastic welder for this repair. The key is to have a good weld gun that has temperature control. I've use both the regulated air supply guns and the self contained blower/temp control ones. You can throw away the air regulated ones. They are just to difficult to get a uniform weld with.
Here's a good primer on plastic welding.

http://www.malcomheatguns.com/downloads/files/Plastic%20Welding%20Instructions.pdf

This is a good choice for an inexpensive welder: http://www.harborfreight.com/plastic-welding-kit-with-air-motor-and-temperature-adjustment-96712.html

The location of your cut doesn't look like it would be to difficult to weld.

BTW you want to weld that HDPE at 300-370 F.

stormbytes · Mar 17, 2012

Chet18013 said:
I'd definitely use a plastic welder for this repair.

I crawled under the belly of the Winnie today to prepare the site for the upcoming repair. Its obvious the damage has been there for a while. Part of the adjacent side wall sunk into the gash and there were some jagged spots. I preyed the gash apart and manipulated top and bottom sections of the side wall so they bud up against one another, forming a nice clean cut. While there, I explored the rest of the tank and Murphy's law being what it is, I found yet another cut. This time in the side wall that faces the front of the coach. Its not as bad as the first, only 3-4 inches long and perfectly straight.

Earlier in the day I spoke with a savvy technician at TAP Plastics who said Poly-Weld was formulated specifically for PP/PE thermoplastics, with tensil strength in excess of that of the tank. I'm gonna go with that and hope that solves my problem. Time and money (and frustration) being major contributing factors.

John From Detroit · Mar 17, 2012

Years ago there was a man who had a hole in his favorite tennis shoe, So he made a product to fill it with so he could save it's sole. SHOE GOO.

Today it comes in several "Flavors" called GOOP, a direct descendent the different GOOP Formulas have slightly different features.. I'd try Plumber's or Automotive.

NOTE: Though I have not used it on a black tank REPAIR.

I did use it on a Tornado flusher install.. So far, no leaks, several years.

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