Can plumber’s putty be used on plastic?

I keep my dishwasher pods under my sink. One night, I finished loading the dishwasher and went to grab a dishwasher pod and found the cabinet slightly damp. Having just renovated my kitchen, it seemed unlikely that it was a leak. I removed everything from under the sink, dried it with some towels, and replaced it all. When I was doing dishes, I obviously spilled some water over the ledge of the sink and it leaked through the cabinet door. Right?

A little backstory: kitchen renovations are expensive. To combat this, my husband and I decided to do some of the work to cut down on the costs. It saved us thousands of dollars, but without the proper research, there are simple mistakes that were made in the process. Specific to this scenario: we used PVC pipes and plumber’s putty. These two should never be used together.

Can plumber's putty be used on plastic

Today, we’ll look at why you should never combine plastic pipes and plumber’s putty. We’ll also take a quick look at other times that plumber’s putty should not be used, and what you can use in place of the plumber’s putty so you don’t have the same leakage issue I did!


What Is Plumber’s Putty?

This product has been used for several decades since its inception. Plumber’s putty is a malleable putty that softens as it makes contact with your hands. This compound works best for joints that need to remain water-resistant. To keep the putty soft, linseed oil, fish oil, or petroleum oil are used as part of the formula. It remains soft even after years of being in place. This is fantastic because if it were to dry and crack, it would cause leaks.

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Never Use Plumber’s Putty on PVC

People may tell you that plumber’s putty is always best for sealing pipes. Not only does it remain pliable after years, but it fills larger gaps much better than caulk would. However, there are times when plumber’s putty is best not used.

One of these times is when using plastic piping. The reason that plumber’s putty should not be used on plastic is because it is made using petroleum oil, which deteriorates PVC over time. Any compromise to the structural integrity of the piping will cause leakage. Plumbers find that even the most rigid of plastics become brittle when exposed to plumber’s putty.

Can plumber's putty be used on plastic pvc

Also, Never Use Plumber’s Putty…

There are other times when plumber’s putty is not a good option for plumbing. Some people may believe that plumber’s putty is a perfect fix-all, almost like the duct tape of the plumbing world. This isn’t true, though. For instance, never use plumber’s putty to seal the back of a bathroom sink to the wall. This will not dry, so it will never provide the proper seal you are looking for. Instead, use a silicone-based caulk. In fact, never use plumber’s putty when it will be visible. Over time, the coloring may yellow and create an unsightly look for your finished product.

Never use plumber’s putty on threading. You should only use Plumber’s tape, also called Teflon tape, for threaded pipes, which will properly create a watertight seal that you cannot get with the mailable putty. This tape is specifically made to provide the proper adherence between pipe threading. It can also be used on both plastic and metal pipes that are under high-pressure circumstances, like drains.

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Can plumber's putty be used on plastic? plumber's tape

In the same line of thinking, never use plumber’s putty to connect pipes. Again, plumber’s putty never fully dries out, so it will not provide the adhesive strength you need when combining two pipes. If you use plumber’s putty for this job, the weight of the pipes will pull on the putty and eventually come apart.

Do not use plumber’s putty underwater. As amazing as this product is, it will not adhere to a surface underwater. Remember how this is water-resistant? Well, if there is moisture between the putty and the surface it is touching, it will not connect properly.

Finally, it is highly advisable to avoid plumber’s putty when working with marble, granite, or other porous stones. The reason for this is the petroleum oil we mentioned earlier. Over time, the petroleum oil will leak into the porous stone and stain these surfaces a yellow or brown color. That being said, there are versions of plumber’s putty that are water-based and are intentionally made to work with porous stone and stainless-steel products.

Instead, Use…

Silicone caulk is often used by plumbers today. Not only does it also keep everything watertight, but it also provides heavy adhesive properties that plumber’s putty does not. Just like plumber’s putty, silicone caulk remains flexible with time and will not crack.

Most new drains come with a rubber gasket that can be used in place of plumber’s putty under the flange. However, some plumbers still prefer to use plumber’s putty along with the rubber gasket since the flange can deteriorate over time and need replacing.

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PVC primer is the best option for connecting plastic pipes. This primer is typically made of acetone and cyclohexanone. The acetone or tetrahydrofuran in the PVC primer will remove the outer sheen of the pipe and create a rough exterior that works perfectly to make PVC glue stick. This will create a tight bond that will prolong the life of your plumbing.

Other adhesive products, such as tub caulk or marine adhesive, are great options in place of plumber’s putty. These products typically come in a squeeze tube for easy application. These products may be better at stopping leaks, sealing visible spots, or connecting plastic to other surfaces. Be sure to read the back of all products to decide which will work best for your project.