PVC coupler dry fit is too tight --- will cement lubricate it?

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Bromel

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I am working with PVC welding for the first time. I am raising the height of a toilet flange using a coupler and a new section of 3" PVC. The coupler does not slide "easily" onto the PVC pipe. It goes on to the shoulder all the way, but with considerable effort. I've never used PVC glue before. Will it lubricate the coupler and allow it to slide on more easily? Or do I need to sand down the surfaces so they slide together more easily?

Thanks.
 

Terry

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Neither ABS or PVC will "dry fit".

When you prime and glue the PVC, it will fit together fine.

PVC,
1) first use the purple primer
2) then the glue.
Coat both the pipe, and the inside of the fitting with both primer and glue.
3) push together with a swerving motion. This smears the solvent between the pipe and fitting better.
 
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Dunbar Plumbing

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If you use glue it is going to become a permanent situation. Gauge your pipe cuts first by measuring socket to socket, then use cleaner and glue and make your connection.

Holding the pipe to the side is a better way to gauge correct pipe lengths. Dry fitting is more time consuming and doesn't always guarantee a correct fit, especially if you don't push the pipe to the stops.
 

Bob NH

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Don't sand the surfaces.

I'm surprised that you were able to seat the pipe to the shoulder, but maybe with some DWV fittings that is possible. It is never possible with Schedule 40 pressure pipe fittings.

I have a process that has never failed me in PVC assembly:

1. Cut the end square, using tools as necessary consistent with skill.
2. Deburr the end of the pipe.
3. Prime both parts with purple primer, but don't let it puddle in the socket.
4. Apply cement to the female part, then the male part. No puddling; no holidays.
5. Insert the parts, forcing to the full depth of the socket, with a 1/4 turn while inserting.
6. Hold in place for a few seconds so the taper of the fitting doesn't push the part out of the socket.
7. Wipe away excess cement.
 

Jadnashua

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SHort answer...the cement actually melts the top layer and then when the solvent evaporates, it is welded together. SOrt of like airplane glue.
 

hj

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Pvc

When you said "PVC welding", I wondered why you would be doing that, since it is not a DIY process, but then I realized you meant gluing the parts together which is a different process althogether. The parts will go together once the primer and glue are applied, although sometimes it takes a "swift kick" to push them all the way into position.
 

Prashster

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As a fellow diyer let me offer some hard learned advice: don't dry fit. Measure twice socket to socket. The primer and cement will DEFINITELY lubricate and give you a deeper fit than dry fitting. If you rely on dry fitting (as I did for my vents), you'll end up cutting yr pipes too short.

Also, make sure you purple prime. It's tempting to save the mess and the step, but it really makes a difference - especially if the system is going to have to be pressure tested.

Last, when you cement the pieces, push the pipes together and hold them for 30 seconds. The heat generated by the cement melting the plastic will try to force the pipe apart until the cement dries. If you let the pipe pull apart and reseat it too much - even a few mm - it won't fuse properly.
 
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