If you’ve put a PVC pipe on a threaded joint, it could be leaking for a number of reasons. For example, it might be leaking because of over torque or if it’s on crooked. However, there are a couple of very easy ways to fix the joint if your threaded pipes are leaking.
In some cases, threaded PVC joints leak because the threads are stripped. On the other hand, in other cases, it’s because the pipe isn’t on straight. Either way, you can take it off, re-apply it, test it, and if no change, either seal or replace the threaded joint. In most cases, a replacement joint costs a few dollars at most and ensures a better seal – even if your threads are stripped. Otherwise, there are a few easy ways you can try to fix a leaking threaded PVC joint.
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How to Fix Leaking Threaded PVC Joint
If you have PVC or ABS pipes, you can try the following repair methods to fix a leak in a threaded joint. However, if you have a CPVC pipe, you’ll want to take the leaking section out and replace the section.
In the following section, we’ll cover how to fix leaking threaded PVC joint sections, with four different methods and when each is a best fit.
Fixing leaking pipes with repair epoxy
Epoxy is the easiest way to fix a leaking threaded joint without cutting the pipe. This method is also suitable if you have a cracked pipe or joint. Repair epoxy is a 2-part compound which you mix together and mold into a putty. You then press it into the seams to form a tight seal. Once the epoxy hardens, it forms a watertight seal. This makes it an ideal solution if your pipe has cracked, if you’ve over-torqued the PVC joint, or if you’ve already glued the joint on and it’s leaking.
You’ll need:
- Gloves
- 2-part repair epoxy such as Waterweld, KombiPlastic, etc.
- Cleaning supplies
To fix leaking pipes with repair epoxy, you’ll want to thoroughly clean the surface. Here, it’s best to use acetone or a similar harsh cleaning agent. Use cotton swabs to get as far into the joints and cracks as possible. You’ll also want to make sure the surface is dry and that the water is turned off. Then, mix the putty or liquid according to the manufacturer’s instructions. Follow the instructions on the package and work the substance into the joints and cracks. From there, you can allow it to dry. Your leaks should be fixed.
Fixing leaking joints with fiberglass wraps
Fiberglass wraps are relatively new to the market. However, they’re a good way to repair leaking pvc pipes in tight spaces. This method is also ideal for fixing cracks or for fully sealing the outside of a pipe joint. For example, if there’s a crack in the pipe or if there’s too much tension on the side of the pipe for it to seal correctly.
Fiberglass wraps combine epoxy resin and fiberglass tape. Here, you mold the epoxy and apply it to the pipe. Then, you wrap it around the outside of the pipe. It normally cures in 30-90 minutes, giving you a watertight seal.
This is another great way to repair leaking threaded joints without cutting the joint. However, you’ll have to ensure that you get the epoxy and the fiberglass wrap as far into the joint as you can. Otherwise, water will sit between the pipe and the wrap.
Sealing PVC threaded joints with Teflon tape
Teflon tape may be used to seal PVC threaded joints, especially if you’ve over tightened them. However, it should not be used as a standard. In fact, using Teflon tape to seal PVC pipes is the easiest way to get leaks. Why? PVC pipe is soft. If you over torque it, which means over tightening it, you’ll strip, bend, or even warp the threads. Then, they leak. Your first sealant should always be pipe dope, also known as thread compound, or pipe thread sealant.
However, you can only use this method if you haven’t glued the pipes. You’ll need a role of Teflon or P.T.F.E. tape. Because most PVC pipes are quite large, you’ll want to find a roll that is as large as possible. Then, you’ll want to wrap the tape so that there is an even three layers across the full length of the joint. From there, you can screw the pipe joint back into place. Slightly tighten it once it gets difficult to turn but don’t over tighten it.
Replacing the joint
If your drain pipe is leaking at the joint but you’ve already glued it, you might have to cut it out. In fact, if you have a cream-colored drainpipe, it’s probably CPVC, which is very difficult to repair properly. In this case, cutting the joint out and replacing it might be the best way to fix leaking pipe threads.
You’ll need:
- Hacksaw capable of fitting into the space
- 2 connectors for your PVC pipe size
- A new joint matching the old one
- Pipe dope or pipe thread sealer
Make sure the water is turned off. Then, use the hacksaw to cut the pipe above and under the joint. If your leaking threaded joint is close to a wall or fixture connection, it’s better to take the pipe out from the joint to the wall. Then, you can replace the whole section. This removes the need to have connectors, which can throttle drains and water suppliers.
Once you’ve cut the old section out, add in connectors or new pipes. Glue them in. Then, put your new joint(s) in place. Here, it’s important to use pipe dope to seal the threads. You’ll also want to pay attention to not over torquing the connections.
How to Seal a Threaded Pipe Joint
If you’re installing new threaded pipe joints, it’s important to install them with care. PVC pipe is relatively durable. However, PVC threads are thin and delicate. Applying a large amount of force when twisting them on will heat and warp the threads. This is called over-torquing.
You’ll also want to use the proper thread pipe joint sealant. This is “pipe dope”, which is sometimes sold as “thread sealant” or “thread seal”. It’s almost always available in the hardware store, next to the PVC pipes. However, not all pipe dope is intended for PVC pipes. You’ll want a non-hardening plastic pipe sealant.
Finally, you’ll want to ensure that you turn the pipe on straight. If the pipe is even slightly crooked, it means it’s not fully locked into the threads. This will cause problems like leaks. If this is the case, carefully twist it off, apply new sealant, and twist it back on to see if that solves the problem.
Why Do Threaded Pipe Joints Leak?
Threaded pipe joints can leak for a variety of reasons. The most common is over torquing. Why? PVC pipe threads are tapered. Here, the American National Standard B2.1 defines that all pipes have a 1 ¾ degree taper on the threads. So, female threads get successively smaller as you go down the pipe while male joints get successively larger. If you over-torque the pipe, you’ll literally split the bottom threads.
Of course, you might also have leaking joint because you’ve twisted the pipe on sideways. Or, the joint might be cracked. Or, you might have used a hardening pipe dope as a sealant. This can harden and crack the threads as it dries. Therefore, you should always use a non-hardening sealant on PVC pipe.
Finally, there’s always the possibility that your PVC joints are leaking because you’ve mixed Schedule 40 and Schedule 80 PVC pipe. These pipes do not have compatible threads, so putting these two joints together will result in a leak.
FAQ
If you still have questions, this FAQ might help.
What’s the best PVC pipe leak sealant?
In most cases, the best PVC pipe leak sealant is repair epoxy. That’s also true if you want to know how to fix a leaking threaded joint without cutting it out. Epoxy putty can be forced into all of the gaps around the pipe, effectively stopping the leak.
However, epoxy putty is also not cheap. It may be cheaper to cut the joint out and replace it. However, if you have high water usage, using a connector might be a bad idea because it narrows the joint. Instead, you might want to take out everything above the joint and put in a new joint and new lines.
How to repair a leaking glued PVC joint
If you’ve glued your PVC joint in place, you’ll want to use epoxy putty to repair the leak. Otherwise, you’ll have to cut the joint out to replace it.
Can I use Teflon tape to fix a threaded pipe joint leak?
You can use Teflon tape as a last effort to fix a leaking pipe joint. However, it’s difficult not to over torque with Teflon tape in place. In addition, if you put too much tape on, it could cause the joints to split. Make sure you don’t use more than three layers. In addition, you’ll want to avoid any mechanical tightening. PVC pipe never needs more than finger tightening.
Conclusion
Hopefully this guide taught you how to fix a leaking threaded PVC joint. In most cases, you’ll want to use epoxy putty or will want to replace the joint. Otherwise, there are some other repair options you can try. And, when you put the joints back together, make sure you use a PVC-appropriate pipe dope and take care not to over-torque the joint.
