Plumbing holding tank connectors

[Dockhead]

Originally Posted by vladkri

Darn it. I'm sure they could weld pickup tube from the top. Never occurred to me. Oh well. About teflon tape, just to confirm, it's several layers on each mm of the thread or several overlapping wraps covering entire thread except first few?

Don't use teflon tape on plastic threads.


Teflon tape works on metal threads by lubricating the threads enough so that the threads can be snugged down so much that they seal. This doesn't work with plastic threads.


You should use pipe dope on plastic threads.

[Dockhead]

Originally Posted by vladkri

Greetings. I'm going to install brand new custom made plastic (PET) holding tank. The manufacturer provided me with various PVC thread-to-barb connectors which I'm supposed to screw into threaded holes in the tank. The one I'm worried most is the pump-out port at the very bottom of the tank. How do I ensure it 100% will not leak? . . .

Not to sound flip, but by sending the tank back and ordering one with only top mounted fittings.

I would never have a holding tank with an opening in the bottom. Or any other tank on a boat. Especially not a holding tank.

[vladkri]

Originally Posted by Dockhead

Don't use teflon tape on plastic threads.


Teflon tape works on metal threads by lubricating the threads enough so that the threads can be snugged down so much that they seal. This doesn't work with plastic threads.


You should use pipe dope on plastic threads.

Any brand advice?
I look at "Datey" and it says do not use on plastic pipes. One teflon roll (pink) indeed says the same thing.

[Dockhead]

Originally Posted by vladkri

Any brand advice?
I look at "Datey" and it says do not use on plastic pipes. One teflon roll (pink) indeed says the same thing.

I think most of the brands are local. I have been using Unipak, but I think that may be Northern Europe only.



In these parts, it's customary to use the very ancient traditional method of sealing pipe threads, with some hemp fibers added to the pipe dope. It works really well.

[Cheechako]

Originally Posted by vladkri

Darn it. I'm sure they could weld pickup tube from the top. Never occurred to me. Oh well. About teflon tape, just to confirm, it's several layers on each mm of the thread or several overlapping wraps covering entire thread except first few?

A Bottom pumpout fitting worked very well for me. No clogging issues either! I wouldn't do it any other way.

Teflon tape should work, but as Peggy says several wraps. Not a huge fan of it with plastic though. Be careful, you can just keep tightening until the fittings deform because the teflon is so slick.
I have used the teflon pipe joint compound/dope instead at times. Messy.

[goboatingnow]

I have a bottom exit to the holding tank. Works great

[Near2KR]

In the US pros use Rectorseal

[rwidman]

Originally Posted by Dockhead

Don't use teflon tape on plastic threads.


Teflon tape works on metal threads by lubricating the threads enough so that the threads can be snugged down so much that they seal. This doesn't work with plastic threads.


You should use pipe dope on plastic threads.

Plumbers use Teflon tape on plastic threads day in and day out. It's standard procedure and works just fine.

[rwidman]

A properly installed and connected outlet at the bottom of the tank will not leak. It's not something to worry about.

[peghall]

The advantage to a top-mounted discharge line is, it eliminates standing sewage in the discharge line. When the discharge fitting is at the bottom of the tank, waste rises in it to the level in the tank, resulting in a permeated hose unless hard PVC is used to the top of the tank...making it easier just to put that piece of pipe INside the tank.



--Peggie

[vladkri]

Well, the thing is installed. I went for Rectoseal. The blue goo. Thanks for the tip. Seems fine for now. I also contacted the tank manufacturer and they could weld pumpout tube from the top thus eliminating under "water" connection altogether. Too late for me now. Overall it looked like a daunting job, but with all the materials being collected beforehand it was not such a big deal. Luckily nothing had to be demolished in the process.