Sealant for holding tank & dump fittings?

[wayner1239]

I ordered a new waste water holding tank and am not sure what kind of sealant to use to connect the flush valve to the tank. Airstream tech said that the tank was made of polyurethane. That was a big surprise to me because I thought holding tanks were made of ABS or polyethelene. Fittings on the old tank were joined with some kind of hard clear looking stuff that has to be cut away. Whatever it is it would be ideal to repair old tanks.
I would also like to know what kind of sealant to use for the dump fittings. I believe those fittings are ABS. The old fittings appear to be joined with a thick black sealant. Whatever it is I cannot get the fittings apart.
All suggestions or comments are appreciated.
Wayne

[davidh]

I'm sure they used some type of pipe thread dope, if you cannot get it to turn, you might half to use a little heat on the joint to soften up the pipe dope, just heat enough to warm up the joint and then get a pipe wrench or what ever works, something with leverage so you can turn the valve. then use pipe dope or teflon tape when you replace valve.. I just reread your thread again and you might have glued joints and I am thinking now that you do, you can buy the Glue and Cleaner at any hardware store, the only way you will get it apart is to use a handsaw to cut the pipe, if you have a picture of it to post that would be of great help to figure out what you have and the best way to approach it..

[davidh]

one other thing that you should know, if you have PVC Pipe and you cut a short piece to go in between the tank and valve make sure that you cleanup all the sharp burs off both ends of the PVC Pipe, if you do not do this, a bur can catch the toilet paper and plug the pipe.

[john hd]

wayne

my 1992 excella has good old vulkem between the tank and the valves. secured by a heavy duty aircraft hose clamp.

search for my thread on grey water tank repair. lotsa pics.

john

[wayner1239]

My original post was confusing. I wish I could attach a picture but my old sony mavica stores pics on a floppy disk and my new laptop doesn't have a floppy drive.
Instead of flush valve, I should have referred to the tank rinse valve where the rinse water line goes into the tank. The rinse fitting is held against the tank with a flange that is screwed into the tank. There is some kind of sealant behind the flange. I am not sure what kind of sealant I should use on the new tank.
The sealant on the dump fittings is probably vulkem as John said. It is a thick substance that doesn't completely harden. I have never used vukem because I have never seen any at hardware stores, building supply stores, or rv supply center.
I will try David's suggestion and try heating the fittings to take them apart. Thanks for the help.
Wayne

[davidh]

Wayne keep us up to date on your progress..

[lewster]

Originally Posted by wayner1239

My original post was confusing. I wish I could attach a picture but my old sony mavica stores pics on a floppy disk and my new laptop doesn't have a floppy drive.
Instead of flush valve, I should have referred to the tank rinse valve where the rinse water line goes into the tank. The rinse fitting is held against the tank with a flange that is screwed into the tank. There is some kind of sealant behind the flange. I am not sure what kind of sealant I should use on the new tank.
The sealant on the dump fittings is probably vulkem as John said. It is a thick substance that doesn't completely harden. I have never used vukem because I have never seen any at hardware stores, building supply stores, or rv supply center.
I will try David's suggestion and try heating the fittings to take them apart. Thanks for the help.
Wayne

Wayne,

Try Vintage Trailer Supply as a source for the Vulkem. Sika-Flex would also work well, as will 3-M 5200 marine sealant.

[balrgn]

I would use caution using anything that would permanently harden if you want to get it apart again in the future... I used a sealant that gets tough but is flexible. To disassemble the joint, you should use a heat gun or just a hair dryer to make it flexible enough to come apart....

Rector Seal is amazing stuff.. Tite Bond is good to, Plumbing stores should carry both

http://www.rectorseal.com/slnts.htm

[wayner1239]

The new tank was not too much of a problem getting back in place. We took it on a short trip and everything worked great. I used aluminum backed eternabond to seal along the edges of the underbelly that I had to replace, and it appears to seal very well. Thanks for all the help and ideas.
Wayne