Patching several cracks in blackwater tank?

[Bill Hime]

Does anybody have experience with patching cracks in blackwater tank. Leaving in 12 days! Last things to address is plumbing!




Bill

[Rickf1985]

Best thing to do here is go to the search bar upper right while in this thread and type in Black tank repair, or tank repair. There have been several treads on the subject.

[Rickf1985]

Sorry Bill, I followed my own advice and got nowhere. I even search the main forum and could not find the threads I was looking for. There are threads by Dave (imagine that) about plastic welding on tanks. It basically tells you that you need to use the same material as the tank is made of to do the repair. Since you have been in contact with Dave I suggest you ask him about this. you can blame me if he does not know. I am pretty sure he wrote up the article though.

[WrigleysBraveWin]

Does anybody have experience with patching cracks in blackwater tank. Leaving in 12 days! Last things to address is plumbing!

Bill

Any pics of suspect leak locations?

[Rickf1985]

For leaks or posts? The posts are in this plumbing section somewhere.

[Rickf1985]

Here is one, I just scrolled down through this section.

http://www.classicwinnebagos.com/forum/index.php/topic,12822.0.html

Found it! This is the one I was looking for.

http://www.classicwinnebagos.com/forum/index.php/topic,3611.0.html

[CapnDirk]

I've been in automotive (mechanical and bodyman) for decades.  The best stuff for plastics repair is from Fusor.  I fix plastic (mostly what cars are made of) on a daily basis.


https://www.lord.com/products-and-solutions/brands/fusor-repair-adhesives

[DaveVA78Chieftain]

As Rick said, I have found Plastic Welding to be the best solution.  I have never been able to get any form of adhesive stuff to stick for very long on the plastics the tanks are made of.
Fresh Water: polyethelyene (ice maker water tubing) for food grade plastics.
Black: ABS or polyethelyene

In the CW&VRV Search field field enter: Plastic Welding

Note: The Harbor Freight Plastic welding kit is to light weight resulting in the tip breaking off.  I use a 80 watt soldering iron typically used for stained glass solder work

Tank must be bone dry in area of repair or the moisture will steam up leaving air bubbles in the repair resulting in leaks.

[joev]

Other option is to order new tank i replaced my grey water tank orderd it direct from winnebago cost was 240 dollars direct fit they keep all the moulds of everthing they made only took 2 weeks to get it when i got my tank it was a direct fit only 20 mins to install used same bolts to bolt it back on  very happyxwith it

[Bill Hime]

Thanks Guys!
My tank is the colorless poly material. My local RV store has this black ABS granules that you mix with acetone, then apply with a putty knife, working it into the cracks...Does this sound like it'll work??


Bill

[WrigleysBraveWin]

Bill - Are there numerous cracks on the bottom or just a stress crack or two .... Pics would help .... but anyways if stress cracks that is a patchable event but if numerous cracks then the miracle cure will not hold .....

If cracks are numerous but in one location, say the bottom, then a short option would be to find a piece of material that could cover said area, some flexible but fairly thick pvc type polysheeting of some sort - set sheet in water cut off and then strip in the four edges with Eternabond - cleaning of said area is extremely important before any repairs can start - you'll also to wanna "scratch surface" before applying any material, even one from RV Dealer .... but personally a new tank maybe in your best interest ....

If stress crack or two, that is another story on how to repair  ..... Few pics would be great help in helping you!

[Bill Hime]

thanks Wrigley,
I'll get some pics tomorrow morning. I would love a new tank but budget has to get us road-worthy first. I think dropping it out to work on it would be the next step...if it's not patchable then there's no reason for it to be under there!


Bill

Note: We also have a gas tank to deal with...more to come on that!!!

[TerryH]

Hope, for your sake, neither are full!

[DaveVA78Chieftain]

White (colorless) is normally polyethelyene.  ABS is normally black.  They are dissimilar plastics.  Not sure if ABS can be used to mend polyethelyene.  The acetone melts the plastic such that a blended patch can be made.

[boohoo222]

i used flextape on a pressurized water tank over a leaking crack, it works fantastic and you dont need to empty tank and it dosent need to be dry, but once you slap in in place dont expect to ever take it off, its there to stay

[skloon]

I used a mobile plastic welding guy once he charged by the inch and was fast he also told me that one tank ws made out of some weird plastic that was unfixable and saved me time and money trying

[Oz]

I would guess that was the milky white, polyethelene,  I think it has some kind of weird, oily (or something) makeup that makes it really hard to seal with most typical methods of repair.  The PO had actually sealed the entire tank with fiberglass to try to fix it!  Guess what... it still had leaks and, after some grueling work removing most of the fiberglass (the hard part was just cutting it off... it didn't actually stick to the plastic), I found it had numerous cracks, mostly around all the stress areas which had grown over the years.


Dave's post on plastic welding is fantastic.  Any home-grown, classic RVer can learn how to do it quickly and do it effectively. 


Of course, the first question is. how badly is it cracked?  Is it just a few cracks or does it look like a spider went crazy on it?


If it's the latter, replacement would be best as it's highly likely that, even after taking hours to do all the repairs, more cracks would develop.