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Old 06-14-2016, 09:09 PM   #1
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Need help solvent-welding 4" PVC


This is a pretty long post. Sorry but I don't know what info is relevant and what isn't so I'm including all of it.

I am in the middle of a project to replace some 4" cracked cast iron sewer pipe with PVC. This is my first time working with PVC cement and the 4" sized pipe.

I bought Oatey 8oz Heavy-Duty Cement from Home Depot, and the Oatey purple primer. I watched the
on youtube, and also read Weld-On's Solvent Welding Guide (the 2013 version with real pics and not the cartoons).

I tried, twice, to connect two 4 inch PVC 45 degree street fittings together. In both instances I followed the written directions and the video directions and did what they did. I chamfered the spigot (pipe-end) 3/32 10-15 degrees using deburring tool Reed DEB4. I applied primer to hub then spigot then back to hub. Then I applied cement --liberally-- to spigot then hub then spigot again. I worked quickly, quicker than in the video.

The first time I got the one fitting while rotating into the other barely an inch before it just stopped moving. No amount of strength could get it moving. And I'm telling you I put my all into it. The second time (different fittings) I got it in all the way but only after putting all my weight on it, literally. But I couldn't turn or move it to the angle I wanted.

Here's a pic of the first time and one of the second time. The first time there's a huge gap and the second time there is a 3/16" gap but I think that is normal since the hub is tapered. The little bits of plastic are from me cutting it up with my miter saw afterwards.




If you've made it this far thank you for reading, I really appreciate it!

In the past I've worked with PVC up to 2 inch and I've never had a problem like this. I was able to just glide the pieces together and hold them like in the video.

I'm thinking there are three things I could do differently:

1. Use a larger dauber: The daubers in the 8oz cans are small, an inch or less. So it requires multiple dips to coat a 4 inch pipe. Instructions say use a dauber half the diameter of the pipe but nobody seems to sell 2 inch swabs. I found some 4 inch superswabs from Weld-On and I ordered them. I figure I can cut them in half and fasten them to a wire hanger or handle.

2. Bevel the pipe: I have an old pipe beveler, Pilot Tools UPB-112 (see brochures here), and I figure if I sharpen the blade I could use it to bevel the pipe-end (spigot on a 45 street in this case) a lot more. Doing that doesn't seem to be explicitly forbidden but I don't know if it's worthwhile. If I bevel away enough material (pipe beveler manufacturers recommend beveling to half the thickness of pipe wall) could that create a weaker joint?

3. Use medium-setting cement: Like this Weld-On Gray 782. I can't find it at Home Depot so I'd have to order it. I don't know how long that will give me before I can no longer move the parts.

Does anyone have any ideas what I could be doing wrong, or any suggestions for how to solvent-weld 4" PVC? Thanks

Last edited by Deck; 06-14-2016 at 09:16 PM.
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Old 06-14-2016, 09:15 PM   #2
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Re: Need help solvent-welding 4" PVC


Buy the 32 oz primer and glue the daubers are larger and it will work better.
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Old 06-14-2016, 09:47 PM   #3
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Re: Need help solvent-welding 4" PVC


Yep, bigger daubers. I put glue on the pipe first, then fitting, then another coat on the pipe. Don't be stingy when putting glue on the pipe
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Old 06-16-2016, 10:30 AM   #4
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Re: Need help solvent-welding 4" PVC


As E mentioned dont be shy with the pvc glue your glue is your lubricant before it is your glue.
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Old 06-19-2016, 11:27 PM   #5
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Re: Need help solvent-welding 4" PVC


I got a good connection. I used one of the super swabs and made sure there was a lot of glue on the pipe end as suggested. Also, I made a jig and used locking chain clamps to lock one piece to the jig and lock another piece to a 4 gauge angle bracket. I inserted by making the 1/4 turn until I got it exactly where I wanted it and then I used Irwin 12" bar clamps to force the pieces together the rest of the way. Here are some pics, two of the jig and two of the cement and swab:








Last edited by Deck; 06-19-2016 at 11:36 PM.
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Old 06-20-2016, 02:06 PM   #6
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Re: Need help solvent-welding 4" PVC


Holy cow. I have had to use those on 12" pvc before but never on 4". Imagine how long it would take to do a house that way.
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Old 06-21-2016, 01:57 AM   #7
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Re: Need help solvent-welding 4" PVC


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Holy cow. I have had to use those on 12" pvc before but never on 4". Imagine how long it would take to do a house that way.
Well it doesn't need to stay in the jig forever, just until working time passes so that it stops trying to expand apart. The cement causes the pieces to initially want to separate slightly which is why I leave it clamped for a bit.

It's been working pretty well so far, I just cemented a 22 degree fitting today. Here's a pic:

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Old 06-21-2016, 07:35 AM   #8
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Re: Need help solvent-welding 4" PVC


I have glued thousands of joints and have never had to do that. I wonder what is causing that to happen. I have glued 8" and been able to hand push, is the pipe oval ed at all.
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Old 06-21-2016, 02:19 PM   #9
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Re: Need help solvent-welding 4" PVC


The spigots on the fittings are all round and have been chamfered 3/32". Before I started using the jig it was very difficult for me to connect two fittings at the exact angle I want. Having the chain clamps makes it possible so I can adjust it precisely. I can't risk losing any more money to bad angles or expanding pieces.
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Old 06-27-2016, 11:26 AM   #10
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Re: Need help solvent-welding 4" PVC


Are you letting the primer dry before attempting to glue. That may be why you are having a hard time rotating.

But whatever works for you go with it. Be glad you dont have to do a whole house that way.
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Old 06-27-2016, 12:52 PM   #11
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Re: Need help solvent-welding 4" PVC


Quote:
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Are you letting the primer dry before attempting to glue. That may be why you are having a hard time rotating.
It seems to dry like as soon as I put it on. It has a bit of shine but I mean it's not "wet" like the glue.
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Old 06-28-2016, 09:06 AM   #12
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Re: Need help solvent-welding 4" PVC


If your going primer then right to glue that's about the last thing i could think of. You found a way to get it done and that's all that matters.
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Old 06-30-2016, 12:43 AM   #13
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Re: Need help solvent-welding 4" PVC


Thanks for brainstorming. It's coming along.

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Old 06-30-2016, 09:12 AM   #14
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Re: Need help solvent-welding 4" PVC


Something is not right- I made a career out of plumbing and have always been able to simply push the fittings on by hand. You either have bad fittings, bad glue/primer or wrong process.
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Old 06-30-2016, 01:37 PM   #15
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Re: Need help solvent-welding 4" PVC


Ford Field here in Detroit we did 24" pvc from below grade up to the roof gutters. That we had to use come alongs on.
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