How to Ship Water and Other Liquids with the USPS

If you’re thirsty for more knowledge about shipping liquids with USPS, you’ve come to the right place. Shipping liquids requires an understanding of USPS guidelines and restrictions, including which items USPS classifies as liquids. We’ll give you all the basics of shipping and packaging liquids as well as how Stamps.com helps you in the process. 

What are liquids?

Before we get started, let’s define the type of products we’re referring to. Alcohol can’t be shipped with USPS, so we’re only referring to non-alcoholic liquids. Additionally, the following types of liquids can’t be shipped: 

• Flammable liquids 
• Hazardous liquids 
• Liquids with an “obnoxious odor” 

On the flip side, creams and pastes are considered liquids and can be shipped through USPS. You’ll just need to follow the same guidelines as the ones listed above. Liquids, creams, and pastes with push-down tops also need to be mailed using “strong and securely sealed outer packaging.” Push-down tops can potentially open in transit, leading to the damage of other shipments and USPS equipment, so extra precautions need to be taken. 

International liquid shipping restrictions

If you plan to ship liquids internationally, there are a few restrictions to keep in mind. The following items can’t be shipped with USPS to international destinations: 

• Nail polish 
• Gasoline 
• Aerosols 
• Perfume containing alcohol 
• Flammable or combustible paint* 

*Note: Water-based or Latex-based paints can be shipped internationally, as long as they don’t contain hazardous materials. 

Tips for shipping liquids 

Regardless of size, USPS requires packages containing liquids to be labeled on the outer packaging and to include orientation labels to show how your package should be handled. For liquids over 4 ounces, you’ll need to triple-wrap your shipment. 

To triple-package your shipment, place your product in a leak-proof container that covers the original packaging. Then, place the container in a box, like a Priority Mail Flat Rate® Box. It also doesn’t hurt to fill the gaps in-between with absorbent materials. If you’re shipping liquids in glass or breakable containers, it’s best to add extra cushioning materials within the gaps of the box and around your products.  

Shipping liquids with Stamps.com 

Your customers are eagerly waiting for their drinks, makeup, and other products. With branded shipment notification emails and branded tracking, they’ll receive up-to-date tracking information from a customized tracking page. Our recent study showed that 43% of customers want daily tracking updates, so an easily accessible tracking option will help your business stand out. 

Stamps.com merchants can also order free USPS supplies, like the aforementioned Priority Mail Flat Rate® Boxes. These supplies can be shipped directly to your home or business for no additional cost and include supplies for both Priority Mail® and Priority Mail Express® service options. To order free USPS supplies*, simply log in to your Stamps.com account and click the Buy Supplies option on your dashboard. 

*If using Stamps.com Software, click Online Store on the left side of your dashboard. 

Summary: How to Ship Water and Other Liquids with the USPS (Step‑by‑Step)

Shipping liquids via USPS requires following strict packing and labeling rules. Use these steps:

Step 1: Confirm the liquid is shippable

Only non-alcoholic, non-hazardous liquids with no obnoxious odor are allowed. Creams and pastes fall under liquids.

Step 2: Use secure outer packaging and proper labeling

Label the outer package clearly with “LIQUIDS” and orientation arrows. Use strong, sealed containers. For push‑down tops, extra wrapping is required.

Step 3: Triple-package liquids over 4 ounces

Place the liquid container inside a leak-proof closure, then a second container, and finally inside a sealed outer box. Use absorbent material between layers.

Step 4: Add cushioning and protection for fragile containers

If shipping in glass or breakable containers, add cushioning (bubble wrap, foam) in the box to prevent damage.

Step 5: Use Stamps.com supplies and order free boxes

Order free USPS Priority Mail / Priority Mail Express boxes via Stamps.com’s supply section. Use those for liquids shipments.