Good Sam Club Open Roads Forum: Replacing Plastic Water Tank Fittings - How is it done?
Open Roads Forum Already a member? Login here.   If not, Register Today!  |  Help

Newest  |  Active  |  Popular  |  RVing FAQ Forum Rules  |  Forum Posting Help and Support  |  Contact  

Search:   Advanced Search

Search only in Tech Issues

Open Roads Forum  >  Tech Issues

 > Replacing Plastic Water Tank Fittings - How is it done?

Reply to Topic  |  Subscribe  |  Print Topic  |  Post New Topic  | 
Baja Man

Inland Empire, CA

Senior Member

Joined: 02/20/2005

View Profile



Good Sam RV Club Member


Posted: 03/27/19 10:48pm Link  |  Quote  |  Print  |  Notify Moderator

The TH I am purchasing has a cracked fresh water tank fitting. It is the white drain fitting that has a female threaded section where a 90 degree elbow is attached. Fitting/elbow thread are approximately 1/2" - 3/4". It is cracked at the base of the threads. The fitting appears to be plastic welded to tank from factory when new. I read that it is called a "Spin Weld."

I need to remove the fitting and fit on a new one.

How can it be done?
Is it only done by "spin welding?"
Are there other methods of a proper repair?
I would prefer to not have to remove water tank.

See pics below.....owner used silicone to try and stop leak but it did not work.

Thanks!

[image]

[image]


2003 Ford F-350 XLT Super Duty, Crew Cab, V10 (6.8L); 4X2; Standard Bed; SRW; 4R100 trans
2009 Thor-MVP RV- Tahoe 284SA

MitchF150

Puyallup, WA

Senior Member

Joined: 07/13/2002

View Profile


Offline
Posted: 03/27/19 11:29pm Link  |  Quote  |  Print  |  Notify Moderator

What if you took out that white part of the equation?

From there you can probably tell if it's the threads that are leaking or the white thing is cracked or?

Good luck!

Mitch

Lynnmor

Red Lion

Senior Member

Joined: 07/16/2011

View Profile



Good Sam RV Club Member


Posted: 03/27/19 11:39pm Link  |  Quote  |  Print  |  Notify Moderator

If you don't support that valve hanging out there, you will need to repair again and again.





Chris Bryant

Arden, North Carolina

Senior Member

Joined: 03/26/2003

View Profile



Posted: 03/28/19 02:59am Link  |  Quote  |  Print  |  Notify Moderator

Harbor Frieght plastic welder, the cheap one, basically a soldering iron with a big flat tip.


-- Chris Bryant
My RV Service Blog
The RV.net Blog

Ralph Cramden

Not on this rag of a forum

Senior Member

Joined: 06/14/2017

View Profile



Posted: 03/28/19 03:29am Link  |  Quote  |  Print  |  Notify Moderator

Plastic welding may work, or it may not. The issue is the limited amount of surface area of the fitting to weld to, its not the same as welding metal. The bead of melted plastic from welding along the edge of the fitting flange will be much more prone to cracking than spin welding. The issue is the thin plastic tank wall and tank flex. You also have to be good at it, because one wrong move and you just melted a hole through the tank. Its a tricky art and takes practice, even with a good air regulated setup. The HF el cheapo is even tougher to work with.

There is a reason they spin weld fittings to MDPE tanks. In your case you would remove that fitting and spin weld a patch disc over the hole, then spin on a new fitting in a different location. A patch disc is a larger diameter than the flange on the fitting. It spins and melts into virgin plastic around the perimeter of where the original fitting was. You can't pull a fitting off and spin a new one in the same place, The tank is now too thin from the original spinweld and the new one will probably blow right through it.

The collets needed for spin welding are expensive, you would need two, one for the patch disc and one for the fitting. I had a machinist friend make the set I have. Easy to make if you have a mill, most people don't. You also need a stout high rpm router. Definitely need to remove the tank to spin fittings.

A lot of times is just cheaper to buy a new tank. Shop around. I put a 2nd 43 gallon FWT on my Rockwood and found the tank on Amazon for $90, fittings already installed, free shipping. Drop a couple hundred on 2 collets you'll use once?

You can get mixed results by shoemakering on some type of epoxy or glue sealant concoction and cross fingers. That's probably not an option for how yours has cracked on the fitting itself.

The simple fact is there is no glue, adhesive, or epoxy known to man that bonds to Poly, and no solvent to solvent weld it like PVC.

Its a tough nut.

midnightsadie

ohio

Senior Member

Joined: 01/07/2008

View Profile


Offline
Posted: 03/28/19 05:55am Link  |  Quote  |  Print  |  Notify Moderator

x2 and it most likely cracked because theres no support on that pipe hanging out there. pull the tank and be done with it.

folivier

Southeast Louisiana

Senior Member

Joined: 04/15/2007

View Profile



Good Sam RV Club Member

Offline
Posted: 03/28/19 06:05am Link  |  Quote  |  Print  |  Notify Moderator

Here are a couple options:
https://www.amazon.com/dp/B004RCPA2U/?coliid=I17PJAQ8FPZRN6&colid=KNDITYI6UJ2H&psc=0&ref_=lv_ov_lig_dp_it

https://www.amazon.com/gp/product/B007XIMYX8/ref=oh_aui_search_detailpage?ie=UTF8&tag=foreforums-20&linkCode=as2&camp=1789&creative=390957

ksg5000

Oregon

Senior Member

Joined: 06/30/2008

View Profile



Posted: 03/28/19 08:57am Link  |  Quote  |  Print  |  Notify Moderator

Depends on where the leak is. In order to determine exactly where the leak was I removed the tank -- and discovered that the tank was fine but the old fitting had cracked. My fitting just screwed out and I found a replacement at the hardware store.


Kevin

mapguy

Puget Sound

Senior Member

Joined: 09/02/2007

View Profile


Offline
Posted: 03/29/19 08:11am Link  |  Quote  |  Print  |  Notify Moderator

These fittings are usually spin welded. That is the best repair. Agree that a successful repair will involve providing support for the pipe/valve to prevent the spin weld from cracking again.

http://spinwelding.com/products.html

Reply to Topic  |  Subscribe  |  Print Topic  |  Post New Topic  | 

Open Roads Forum  >  Tech Issues

 > Replacing Plastic Water Tank Fittings - How is it done?
Search:   Advanced Search

Search only in Tech Issues


New posts No new posts
Closed, new posts Closed, no new posts
Moved, new posts Moved, no new posts

Adjust text size:

© 2019 CWI, Inc. © 2019 Good Sam Enterprises, LLC. All Rights Reserved. | Terms of Use | PRIVACY POLICY | YOUR PRIVACY RIGHTS