How to Weld a HDPE black plastic water pipe?

[Rock knocker]

Use a 110v mig with flux core plastic mig wire

 

[Sodo]

Main reason for welding this is I don't want to reduce the cross section, I want all the flow I can get. I have a plastic barb fitting Brad, the same one you showed, it reduces the pipe to 1/2".

I've tried melting plastic together before it seems easy but was not inspiring, never remotely strong enough. But as always,,,, hoping to learn a new trick.

 

[rgr33]

I used to work with a company that supplied and installed hdpe pipe up to 18 inches in diameter. Once the initial welding was done, if they wanted to go back in for repairs or splicing a new line in, they didn't re weld, they used compression fitting that slid over the outside of the pipe. That repair did not decrease flow rate.They can be bought at any real plumbing supply store,not sure about availability at Home Depot though.

 

[Sodo]

I know those compression fittings, they are for burial, are reliable. They have strain relief which is necessary once you CUT the pipe. I have used them in the past and I think they cost about $30 each. They are heavy brass with a pair of thinwall stainless steel tubing inserts that don't restrict the flow (much). Thats certainly another option, before burying this pipe I'd cut out the repair & spend the $30 bucks. That reminds me to wrap any 'welds' with red electrical tape as a reminder so I can see it!

One of the reasons I'm looking for options or experience NOT cutting the pipe, so it can withstand tension. With a union, it's only as strong as the union. This pipe goes downhill, I'm often surprised how much tension it gets at times, maybe due to heating/cooling?

I also get animals chewing holes in thinner aboveground pipes, want to learn a quick weld method --- if anyone is doing it (successfully).

 

[Dave M7040]

An important fact about the pipe you have, it is made for MUNICIPAL use such as water lines in subdivisions.
Not all plumbing supply places have the fittings to work with that thick a wall of hdpe pipe.
The supply place you need will be selling fire hydrants, big sewer lines.
When you go to such a place take the second photo with all the label info on it as this is important
Home Depot etc will not have something which will work successfully.
Regular hose clamps cannot squeeze it enough for a long lasting job.
Here is an online place but you may find they dont want to deal with you for an order of one fitting.
Hdpe Supply: Hdpe Fittings, Electrofusion, Polyethylene Pipe, Fusion Equipment
On this site click on the middle item Max-pax to see about one style of fitting which has an insert as others have described
Search Results
Dave M7040

 

[techman]

I have welded tubing for geo heat pump loop installs. There is a too available that you may be able to rent from a geo installer guy. You do not repair the slit, but cut it out and insert a new piece in the gap, and weld it in place. basically the tool has a temp controlled heater. The tubing gets a split clamp heater on the outside to melt it, while the coupling gets a heated insert. Once they are heated for a prescribed time, they are removed from the heater and inserter into each other. A short cooling time and they are welded together seamlessly.

paul

 

[Sodo]

Makes sense that plastic will fuse under the right conditions. Just have to figure out how not to contaminate that fusing layer and the correct temp I suppose. In this case since the cut is sort of 'axial' the pipe still has a lot of strength in tension and the only strength I need onward is burst strength. It's going to see 78 PSI (!) from gravity. Interested in all the knowledge of how to do this. I suppose if I get a good weld I should wrap it with wire or something to withstand burst pressure.

Agreed there are many simple ways to get the water flowing but there is no big rush, prefer to use the time and project to learn something. I have other uses for the knowledge.

 

[/pine]

In these parts...most people that use surface (gravity) water systems use this type of poly pipe...many are unable to bury all the lines...we use a lot of barbed couplers/clamps...when a squirrel etc chews into one etc...I never considered trying to use heat to fix a leak...

Personally if the repair has to be done in the field (rather than on a work bench etc.) I would go with a coupler...

A couple of things I have done are using a torch to judicially heat an end of 3/4 poly pipe to fit over (swadge) 3/4 hard copper...clamps tight, doesn't leak...
...Also in a pinch I've used a short section of the same size poly pipe split lengthwise and clamped the split section over a hole or gouge in a line...it doesn't always seal entirely but works in a pinch without cutting off the service...

 

[Sodo]

Use a 110v mig with flux core plastic mig wire

This is like a 110v TIG with HDPE filler.

Got it welded with a 110v solder gun. I don't know what the wattage is but it was just ---->barely<---- hot enough. Had half a mind to drive to town and buy a 220v soldergun !

Had a little pencil torch for preheat but as I thought the flame starts the plastic on fire, pretty much couldn't make use of it. I was worried that any plastic was overheated (burned) would be weak, so didn't use the torch. I had to pre-melt ahead with the soldergun then go back and fill it, all with just barely enough heat to melt the filler before the preheat solidified. And the wind was blowing.

I used a small piece of 12ga copper housewire for the "tip". And cut filler rod from another chunk of pipe, as suggested.

It was pretty lumpy. I smoothed it out with the pencil torch.

The beast within.

I think I should wrap it continuously with wire, a solid coil around the repair, so pressure won't split it open. It was pretty quick, took way more time to research it than to do it. But it's not done until I wrap it, so there's a little more time. Pretty sure this is gonna work. But I can't say I'd do a repair like this for a customer….this is just goofin' around.

 

[Dishpointer]

If that weld doesn't work, they make a compression fitting that is made for CTS poly pipe that fits on the outside so you won't reduce the flow. Menards carries them.