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Is PETG Waterproof?

Is PETG Waterproof? | 3D Printing Spot

Updated by

William Stone


January 6, 2023

If you like using a 3D printer, PETG filament is one of the best materials you can use. However, you may eventually wonder if PETG is waterproof.

3D printers are incredibly versatile tools that can create 3D objects layer by layer. But what if the thing you’re printing needs to be watertight? Having the wrong filament could really throw a wrench into your plans, so is that PETG filament you have laying around up to the task?

PETG is a waterproof material, so if you need a printed object to be watertight, PETG is a great material to use. However, even though the PETG itself is waterproof this doesn’t guarantee that your printed object will be.

3D printing can be quite complicated and choosing the right filament to use in the right print is just the first step. By nature, 3D prints can be prone to small holes that form in between its layers, so even if the filament you use is waterproof, you’ll still need to be as careful and thorough as possible to ensure that your printed object remains watertight.

As an engineer that does lots of design testing with 3D prints, I’ve worked with and become quite familiar with most of the different types of 3D filaments used in the industry today and PETG is a great option for anyone looking to make waterproof prints.

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Table of Contents

What Is PETG?

Before going into more depth about using PETG to make waterproof 3D prints, it may be useful to learn more about what PETG actually is.

PETG is an acronym that stands for polyethylene terephthalate glycol. Basically, it's a thermoplastic polyester, meaning that when heated it can be formed into any shape you may desire, and as it cools down it will harden and maintain the shape that it was molded into.

By very nature, PETG is incredibly versatile and easy to work with. It's easy to mold in a multitude of ways and  can withstand high pressures without cracking. It’s durable,  and chemical and impact resistant. Not to mention that PETG is a lot more affordable than a lot of similar materials so there’s no wonder that the use of PETG has become common in the world of 3D printing.

Outside of the world of 3D printing, PETG is used in countless products that we use each day, so there’s no doubt that if you have a quick look around your house, you’ll be able to find lots of objects with PETG in them. PETG is non toxic and food safer so It’s used in all sorts of food and drink containers like water bottles and take out containers. PETG is also used in medical device packaging and medical implants as its rigid structure allows any object made from it to be sterilized with ease.

For the environmentally conscious, PETG’s thermoplastic nature also allows it to be easily recycled and reformed into something else,  making it much cheaper and a lot less harmful to the environment than many other plastics.

Is PETG Actually Waterproof?

The answer to this question is a bit more complicated than it looks as it largely depends on what form the PETG is in.

If you have already printed your object with PETG it will no doubt be waterproof, barring any holes that may have formed during the printing process. As you may know, 3D printers deposit filament one layer at a time, piling one layer on top of another until the object is fully formed. However, because of this layering technique, it’s natural for some small holes and pockets to form, compromising the watertightness of your print. However, if this happens and the print shows that it isn’t waterproof, this doesn’t mean that the PETG itself isn’t. The PETG will still maintain its shape and durability.

However, one important thing to note is that PETG filament will quickly absorb water and become brittle if it is stored in a wet or humid environment. That’s why it’s important to make sure that you store your PETG filament in a cool and dry place to ensure that your filament stays in tip top shape until you are ready to use it.

Other Tips For Making Waterproof 3D Prints

As stated before, the method of laying individual layers of filament on top of eachother one by one makes 3D prints prone to tiny holes that form in between the layers. Even if the filament you are using, in this case PETG, is waterproof these little pockets between layers can make it much harder for you print to keep water out. However, there are a few more things you can do to help ensure that your print remains waterproof.

Print Thicker Lines

One of the simplest ways to help prevent water getting through your print, is to simply print thicker lines. The area between each layer of filament is the most likely spot for holes to form. By printing thicker lines you may be able to reduce the number of contact points where the layers meet on your print. If your print has less points of contact between layers there will be less opportunities for leaks caused by the holes that form at these points.This is probably the easiest way to improve the watertightness of your 3D prints.

Add More Perimeters

Adding a few extra perimeters around your print will also help to ensure that your print is waterproof. Even just an extra 2-4 perimeters around your print can make a huge difference in preventing water from getting in as the barrier between the water and the inside of the print will be much bigger.This is another really easy technique that can be done without changing too much on the design end of things.

Over Extrude

Though this may not be the best idea for designs that need to have very precise dimensions and details, over extruding is another solid way to try to waterproof your 3D prints. By simply allowing more filament to pass through the printer allows the layers to merge together more easily. Layers that have merged together properly will stand a much better chance against the water than the ones that haven’t. However, it’s worth mentioning that this will alter the dimensions of your design so this technique is better left as the last resort when it comes to making waterproof prints.

Print A Simpler Design

Though this is definitely not the best option, simplifying your design could be the key to waterproofing your print. Complex designs that include sharp corners, overhangs or any other more complicated details may be a lot more prone to leaks than something with a more simplified design. If you are really having trouble waterproofing your print, a quick redesign may be the best option available to you.

Other Common Waterproof Materials For 3D Printing

If you are really interested in printing waterproof objects, it may be worth noting that there are other materials that are great in this application.

PP, or Polypropylene is another great material to use for making waterproof objects. It's flexible, resistant to heat and chemicals and is waterproof. Not to mention, unlike PETG, PP doesn’t absorb any water, so no need to worry about storing it at ideal conditions. Overall, PP is a great alternative to PETG when it comes to printing waterproof objects.

PP GF30, is similar to PP in that it is waterproof as well as heat and chemical resistant. The big difference here is the addiction of glass fiber which adds strength and allows the material to be much lighter. PP GF30 is another great alternative to PETG if you are designing a waterproof print.

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Is PETG Waterproof?


William Stone

William Stone

William has spent 20 plus years in the custom manufacturing industry as a COO, CEO and Owner of various custom product businesses. His experience has exposed him to all types of manufacturing from die cast, die struck, injection molding, CNC machining, laser etching, engraving and of course 3D printing.

Learn more about William Stone

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