Is PETG Waterproof? How to Print Watertight Parts
PETG is water resistant: once printed it absorbs very little water and handles rain and frost. A print is only watertight, though, if its layers are sealed. A few settings give you containers, watering cans and enclosures that do not drip.
Quick answer: PETG as a material is waterproof. For watertight prints use at least 3 to 4 walls, a slightly hotter nozzle, a little more flow and less cooling. PETG is not suited to water hotter than about 70 °C.
Water resistant or watertight?
Water resistant means the material does not absorb water or get weaker when wet. That is true of PETG. Watertight means no water gets through the part. That depends on how well the layers are fused. Water seeps through poorly fused layers or thin walls, whatever the material.
Note that filament on the spool does pick up moisture from the air and should be stored dry. That only affects printing. The finished print is hardly affected.
How to make PETG prints watertight
| Setting | Recommendation | Why |
|---|---|---|
| Walls (perimeters) | 3 to 4 or more | Several walls close small gaps |
| Nozzle temperature | 5 to 10 °C above your usual | Layers fuse better |
| Flow | 2 to 5% more | Fills tiny gaps between lines |
| Part cooling | Lower than usual | Warmer layers bond better |
| Speed | A little slower | More even extrusion |
| Bottom and top | 5 or more layers | The bottom is the most common leak |
| Filament | Dry | Wet PETG forms bubbles and holes |
Test new settings on a small cup before you print a large part.
Vase mode with a thick wall
For simple containers, vase mode is handy because it prints in one seamless spiral. A single thin wall rarely holds water, though. Increase the line width, for example to 0.6 to 0.8 mm with a 0.4 mm nozzle, and give the bottom enough layers.
Sealing
If a part must be completely sealed, coat the inside with epoxy resin or a suitable plastic varnish. For anything that touches food or drinking water, only use products approved for that purpose.
How to test for leaks
- Fill the part with water.
- Stand it on a dry paper towel.
- Check after a few hours or overnight whether the paper is wet.
- Leaks show up as dark spots. Usually it is the bottom, the seam or a corner.
Limits of PETG with water
- Hot water: PETG softens at around 75 to 80 °C. It is not suited to kettles, hot drinks or the dishwasher.
- Frost: the material copes with cold well, but water that gets into gaps or infill can crack parts when it freezes. Print outdoor parts as solid or sealed as you can.
- Food: printed cups and bottles are not automatically food safe. Use them for plants, the workshop or the garden.
PETG or PLA for water?
Both can be printed watertight. PETG is tougher, takes more heat and lasts longer outdoors, so it is the better choice for watering cans, planters, gutter parts and outdoor enclosures. The full comparison is in our PLA vs PETG guide.
Frequently asked questions
Is PETG waterproof?
The material is. A finished PETG print absorbs very little water, does not swell and handles rain, humidity and frost. Whether a part is also watertight depends on your print settings.
Is PETG dishwasher safe?
Usually not. PETG softens at around 75 to 80 °C, and dishwashers reach similar temperatures during washing and drying. Parts can warp. Wash PETG parts by hand in warm, not hot, water.
Can I use PETG for drinking cups?
We advise against it. Bacteria can grow in the gaps between layers, and the nozzle, color and additives also matter. Food use needs a food-safe coating and a material approved for it.
Why does my PETG print leak?
Usually the walls are too thin, the layers do not bond well enough, or there is slight under-extrusion. More walls, a slightly hotter nozzle, a little more flow and less part cooling fix it almost every time.
