Best repair for a cracked waste tank...

[georgethe painter]

...in a 73 Brave d20t? I have a crack that is visible from the bottom. Pretty good size with the previous owners make shift patch screwed in.I would rather not pull the tank as I will have to disrupt the plumbing. It's a 35 gallon. Any suggestions?

[RedneckExpress]

Well, ideally, you'd remove it to repair it, since its likely made of polypropylene, you have to "weld" it back together using some more of the same plastic and heat/melting tool to "weld" the plastic together. 

I don't know if I'd want to do that from underneath with the hot dripping plastic and what not.

[Oz]

There are plastic welding kits available which include instructions on how to know which type of plastic and welding rod to use.  There's at least one post here which gives at least one link to a supplier, although it is an older post.  I know Harbor Freight has them now too.  You can always Google plastic welding kit as well. 

The fresh water tank in The Chariot was the milky, white type of plastic and had a lot of cracks.  The PO had basically encased it in cloth mesh/fiberglass resin.  It worked but, I must've been quite a laborious task.

[DaveVA78Chieftain]

Plastic welding is not hard.  You just need the soldering iron method where you melt it all back together.  You are not melting the plastic enough such that it is dripping away from the repair spot.  You should only be moving it around in place like soft putty.  Harbor Freight has a soldering tool but use it lightly as I have read the tip can break easily.  Google for plastic welding youtube videos.  Lots of info out there.  You don't need one of them expensive tools unless you want to go into the plastic repair business.  One of the youtube vieos is of an asian repairing a plastic bicycle wheel.  Once you fix your tank, then you can fix your plastic tool box and momma's plastic ware.  After you do all that you will have paid for the tool twice over.

Dave

[georgethe painter]

  My friend has a plastic welder that I am going to borrow. He asked what kind of plastic the tank was made out of so he could get the right rod. It's the previously milky white plastic, injection molded. Does anyone know what type of plastic this is. What's the technical term?  "GTP"

[georgethe painter]

...previously mentioned milky white plastic...

[RedneckExpress]

Odds are its Polypropylene, but, its also possible that its PVC or ABS.  Given that the fact that the last owner had to make a "patch", I'm leaning towards Polypropylene, as nothing sticks to it and the only way to repair it is to do a weld repair. 

[DaveVA78Chieftain]

Most likely polyetheylene (very slick in texture).

Whether polyetheylene or Polypropylene they both are best repaired by welding.

Dave

[tiinytina]

when we cracked our grey water tank at the Jam a couple years ago. we used epoxy for plastic. Cleaned the crack and roughened it, Epoxyed the crack and then used wire to hold the area as tight as possible while it dried. Repeated with a second coat.... then recoated the tank with expanding foam.....  2+ years later and no leaks.... so far....

Tina

[ClassCKing]

our  grey water tank had a peice of the side missing..5inch by 5inch...repaired with fiberglass mess(2 coats after first coat dried )sanded and painted no leaks even did it without droppn the tank..it is alot easier with fiberglass...but messier

[georgethe painter]

Thank y'all very much, I'll let you know how it works out.  "GTP"

[DaveVA78Chieftain]

I have tried the plastic repair stuff and used fiberglass.  Both gave way after a few years.  So now I gonna weld it up all nice and proper.

Dave

[vonsmink]

For Cheep-Id Fiberglass it and take it to a LineX Guy...You will never hafta repair it again

[ClydesdaleKevin]

The tanks on Nautilus are ABS, which are the easiest to repair, at least for cracks.  We had a crack in the black tank when we first got her.  It takes some time, but you just paint on thin layers of ABS cement, which is just ABS powder suspended in a solvent.  (It has to be the cement made for ABS only, the black kind.  Not the multipurpose cement).  You let each layer dry...it drys quick!...and keep painting it on.  It will build up as thick as you want it, and we haven't had a leak since.  If its a wide crack, you can even make a paste with ABS shavings and the cement, and spackle it in there, then once its dry, layer the cement on as described above.  Even a hole is pretty easy to repair, but you need a small peice of ABS material to glue over the whole with the cement.  Let it dry, and layer on the cement.  Easy easy!

Kev