How to Weld a HDPE black plastic water pipe?

   / How to Weld a HDPE black plastic water pipe? #1  

Sodo

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I cut this pipe over the winter with a snowmobile. Dangit. Sure didnt expect so little snow in the Northwest.

Looking for tricks here, lots of clever folks on the internet! Does anyone know if this can be welded? Easily? I know about cutting it out and put in a barbed insert. Thats what I'll do if nobody (with experience) can help me weld it.

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   / How to Weld a HDPE black plastic water pipe? #2  
Cut a scab peice from same materiel to use as a filler. With a powerfull soldering gun(also called a soldering iron) (50w to 75W should suffice), using a flat face tip (if possible), melt the scab peice into the injured gap.
You can use a heat gun on low heat setting to prewarm the region to be operated on.
But first do it on a scrap peice to practice. Inhaling the smoke that will emerge from the gun tip could be hazardous to your lungs. May need to wear a paint booth style mask.
Let it cool off. Then smooth the surface of the repaired area, still using your hot soldering gun.
Turn on the water. Check for leaks.
Finish with plumber's tape (It's a sealing tape). Roll it aroud the pipe starting one to two inches before the repaired gap area, and finish one to two inches past the repaired gap area. When applying the tape overlap by half the tape's width on each turn around the pipe. Done.
 
   / How to Weld a HDPE black plastic water pipe?
  • Thread Starter
#3  
cool thx. I have a 75w Weller & scraps here. No heat gun though, do you think a propane torch can do the preheat? I can imagine the goal is to preheat it through, which the flame is much too hot.
 
   / How to Weld a HDPE black plastic water pipe? #4  
Double barbed coupling all the way. The hose clamps are the most expensive part. It is hard to get anything to stick to PE, even molten PE. If you overheat it the plastic will decompose and become brittle. To weld that tube with no support from inside and not create an obstruction will be another challenge.

There are some new 2-part adhesives formulated specifically for adhering to PE but the cost would be much more than the hose barb repair.

Shop Genova 3/4-in Dia Insert Coupling at Lowes.com
 
   / How to Weld a HDPE black plastic water pipe? #5  
1) cut some strips of the same material. Use a propane torque to melt them in. I learned the hard way: A soldering gun will make you think you've done a good job but not gotten the pipe hot enough to make a good seal. Use a torch.
 
   / How to Weld a HDPE black plastic water pipe? #6  
cool thx. I have a 75w Weller & scraps here. No heat gun though, do you think a propane torch can do the preheat? I can imagine the goal is to preheat it through, which the flame is much too hot.

No problem using the torch, but it is a thad trickier, as you may diform the hose, and it may catch fire more quickly...
 
   / How to Weld a HDPE black plastic water pipe? #7  
I have welded quite a bit of plastic with a soldering gun, but for that and with 60 lbs of pressure on it, I would use the hose barb. I really would.
 
   / How to Weld a HDPE black plastic water pipe? #8  
I have a friend whose job it is to fuse hdpe water mains being installed in new subdivisions.
It is a tricky job requiring precise temp control and special equipment.
I once brought in specialized plastic welders from a big city to weld a large (14'high) plastic tank which came in two pieces so it could enter the building.
Even with their expensive hot air welders, they had about 50 beads of plastic on top of each other before it stopped leaking.
A pipe under pressure will be a much bigger challenge than an ATV fender.
If your weld fails will you be aware of it?
Dave m7040
 
   / How to Weld a HDPE black plastic water pipe? #9  
Yeah, if there is high enough pressure on it, I'd want to use barb sections to repair, despite the fact that they are not perfect either. When doing a lot of irrigation work, I used to get barb fittings with longer barb sections (about 2" worth of barbs on each end) and use two clamps over each barb section. Never had issues with those. Fittings with just a few (3-4) barbs allow the pipe and fitting to get out of line and can leak easier (since the sealing surface becomes slightly elliptical and may run across barbs).

There is a slick welding jig for that pipe, which heats the pipe uniformly. Seen it in use when my geothermal system was installed. The have the ability to heat the pipe ends and the coupler (or fitting) at the same time for the right amount of time, and immediately cram everything together as soon as it comes out of the heater. Makes a real nice and clean looking connection. Guy doing the work told me they never have issues with those joints. I have no idea if that sort of coupling can take high pressure, as I believe the geo loop is mainly just purged of air and not really pressurized very much.
 
   / How to Weld a HDPE black plastic water pipe? #10  
If you have natural gas in your area there should be someone that has the equipment to fuse the pipe together. Just another option.
 
 
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