How do you separate PVC pipe glued together?

PVC (polyvinyl chloride) pipes are commonly used for plumbing, drainage, and venting applications. They are joined together using PVC cement, which chemically welds the pipes together creating a permanent, watertight seal.

Can You Un-Glue PVC Pipe?

Once PVC pipes have been properly cemented together, it is very difficult to separate them. The glue forms a chemical bond that welds the PVC together on a molecular level. Attempting to pull apart glued PVC joints will likely damage the pipe and render it unusable.

There are a few methods that can potentially be used to separate glued PVC, but they are not guaranteed to work:

• Heating – Carefully heat the joint with a heat gun or torch. This can help soften or melt the PVC cement bonding the joint. Heating PVC runs the risk of burning, warping, or damaging the pipe though.
• Chemicals – Chemical solvents like acetone may help break down and dissolve the cemented joint. However, these chemicals can be hazardous to work with.
• Mechanical force – Attempting to mechanically break the joint by twisting, prying, or striking it with a hammer. This often damages the pipe.

In most cases, it is better to cut out and replace a section of PVC pipe rather than trying to separate a glued joint. The methods above should only be tried as a last resort.

Cutting Out Glued PVC Pipe

The best way to separate PVC pipe glued together is to simply cut out the glued joint and replace it with a new section of pipe and fresh joints.

Here are the steps for cutting out and replacing a section of glued PVC pipe:

1. Turn off water supply and drain the plumbing line as much as possible.
2. Using a handsaw, reciprocating saw, or hacksaw, cut the pipe on both sides of the glued joint, leaving a 1-2 inch gap between cuts.
3. Remove the cut section of pipe by dislodging it with a hammer if necessary.
4. Sand and deburr the freshly cut pipe edges so they are smooth.
5. Dry fit the new section of replacement pipe to determine proper length.
6. Apply primer and PVC cement to the new pipe ends and joints.
7. Insert new section of pipe and align properly before cement sets.
8. Allow joints to cure fully before turning water supply back on.
9. Check for leaks once system is re-pressurized.

This is generally the fastest, most effective, and safest way to deal with glued PVC pipe joints. Attempting to separate rather than replace has a high risk of damaging the existing pipe.

Tips for Cutting Out Glued PVC Pipe

Here are some tips to follow when cutting out a section of PVC pipe:

• Support the pipe well on both sides of cut to prevent sagging when cut section is removed.
• Leave a gap between cuts rather than cutting right at joint – this leaves room to work.
• Go slowly when cutting to avoid damaging existing pipe – don’t rush.
• Use a miter box guide if making straight cuts at precise angles.
• Wear safety glasses and work gloves when cutting pipe.
• Use a utility knife to remove any burrs or ragged edges after cutting pipe.
• Dry fit the replacement pipe before gluing to ensure proper fit up.
• Allow glued joints several hours to cure before pressurizing system again.

Separating Certain PVC Joints

While glued joints are nearly impossible to take apart, there are some other types of PVC fittings that can be separated more easily:

• Threaded joints – PVC pipe joined with threaded PVC fittings can be unscrewed. Use caution not to strip the threads.
• Slip fittings – These friction-fittings rely on an O-ring and can be disassembled with some effort.
• Union joints – Designed to be conveniently disconnected without cutting the pipe.
• Compression fittings – Can be cut off or compression released to separate pipe.

So in limited situations where the PVC pipe was assembled without cement, it is possible to take joints apart. But for permanent glued connections, cutting and replacing the pipe is the only real option.

Can You Re-Use Pipe After Cutting Out a Section?

In some cases, the existing PVC pipe can be reused after cutting out a section.

• Straight sections of pipe can often be reused if the cut ends are square and burr-free.
• For pipes with molded fittings, reuse may be difficult since the cut end won’t align with the fitting.
• Short sections of pipe may be too small to reuse after removing a glued joint.
• Visually inspect pipe ends after cutting – damage or cracks mean it should be replaced.
• Only re-use clean pipe free of defects with smooth, sanded cut ends.

To maximize reuse of existing PVC pipe when replacing a section:

• Carefully cut the pipe square using a miter box or guides.
• Deburr and bevel cut ends with sandpaper or a deburring tool.
• Dry fit reused pipe to test for proper fit before gluing.
• Ream or chamfer the interior edges of the cut pipe slightly.

With care, often only the defective glued section needs to be replaced, without requiring a whole new pipe run.

Chemicals to Dissolve PVC Cement

While not generally recommended, some industrial solvents can help dissolve PVC cement joints to facilitate separation of pipes.

Chemicals that may break down PVC cement include:

• Acetone – Often used as paint thinner, acetone is a powerful solvent.
• Methylene chloride – Helps dissolve bonds between PVC cement and pipe.
• Tetrahydrofuran (THF) – Active ingredient in some PVC cleaners and primers.
• Cyclohexanone – Industrial solvent sometimes used with PVC.
• Methyl ethyl ketone (MEK) – A strong solvent commonly used as lacquer thinner.

To use these chemicals to attack a PVC cement joint:

1. Protect yourself with gloves, goggles, and respiratory equipment.
2. Provide ventilation to safely disperse hazardous fumes.
3. Apply solvent liberally to joint with brush or spray bottle.
4. Let solvent soak in and reapply until joint is weakened.
5. Gently twist joint while pulling pipe ends apart.

This method is not reliable and risks pipe damage, so replacing the section is still the best option in most cases. Only use solvents as a last resort.

Heating and Cooling PVC to Loosen Joints

Heating or cooling PVC pipe joints can help loosen the cement bond to aid separation in some circumstances.

Heating with a Heat Gun

• Use a heat gun to warm the glued joint area to 300-500°F.
• Heat softens and melts PVC cement to loosen the bond.
• Avoid scorching or burning the PVC – keep heat gun moving.
• Wear heat resistant gloves when handling heated pipes.
• Gently twist joint while heating to help break adhesive free.

Cooling with Dry Ice or Cold Spray

• Applying dry ice or cold spray cools pipe to -110°F or below.
• Extreme cold can make rigid PVC more brittle and prone to cracking at joints.
• Rub dry ice on joint or spray upside-down with canned air cold spray.
• Repeat freezing and gently prying until adhesive gives way.
• Avoid contact with bare skin – use insulated gloves when handling dry ice.

Heating or cooling PVC can weaken and damage pipes, so avoid temperature extremes. Any heat or cold applied should be localized at the joint area only.

Using Mechanical Force to Separate Joints

For stubborn glued joints, carefully applying mechanical force can sometimes break the cement bond.

Twisting

• Firmly grip and hold the pipe on both sides of the joint.
• Slowly apply twisting force in opposite directions to “break” the joint.
• Avoid creating too much torque or the pipe may crack.
• Work the joint back and forth gently, don’t just forcefully twist once.

Prying

• Wedge a wood block, putty knife, or pry bar into the joint space.
• Carefully apply pressure with the tool to pop the joint loose.
• Take care not to damage the pipe – use only non-marring tools.
• Protective pads can help prevent pipe surface damage.

Tapping

• Use a hammer and wood/plastic block to tap the joint circumferentially around the pipe.
• The vibration can help break the cement bond free.
• Start tapping gently and increase force as needed.
• Be careful not to crack or crimp the pipe walls.

Mechanical methods won’t work on every PVC joint. Try different approaches and use extreme care to avoid damaging pipes.

Conclusion

Separating glued PVC pipe without damage is very difficult. Cutting out and replacing the joint is generally the best solution. With care, sections of existing pipe can often be reused on each side of a cut out joint. Only in rare cases may heating, chemicals, or mechanical force successfully separate a PVC cement bond without pipe destruction. Whenever possible, avoid gluing connections you may need to take apart later by using threaded, union, or compression joint fittings instead.