Hydrostatic Test Methods

Water: Proof, Resistance, Repellant. What’s the Difference?!?

Many people interchangeably use the terms “waterproof,” “water-resistant,” and “water-repellent.” If you’re in the business of marine or awning fabric, it’s important to know the difference and how fabrics perform to these "terms" and learn why these little differences are so important to your job.


For those involved in the marine textile or awning industry, the issue of water and how fabric reacts to it is critical as one of the main reasons people use marine and awning fabrics is to keep things dry. The two common water, or "hydro" issues most important to end-users are water resistance and water repellency. Industry people use these terms interchangeably, but they should not. While the terms sound similar, they are by no means the same, as explained by their definitions.

Water Resistance is the ability of the fabric to keep water from permeating thru the fabric. Water Repellency is the ability of the fabric to bead the water up and have it roll off, thereby not allowing the water to saturate the fabric. Obviously, if water saturates the fabric, it will eventually permeate thru and leak. Here's the caveat: a poor water repellent fabric can have excellent water resistance and an excellent water repellent fabric can have poor water resistance. In case you're beginning to think, "Okay, this is as clear as mud . . .," here are some thought s that will help resolve this murky issue.

A numeric scale to measure Water repellency is something called, "Measured Spray Rating," and is a visual, subjective test. Here's how it works:

  1. A measured, specific amount of water is poured at a 45-degree angle over the test fabric, which is stretched over a circular frame.
  2. After the water is poured, the operator performs a visual inspection of the fabric and compares its saturation to benchmarked fabric saturation photos to determine its final rating. The comparison is then made to an industry-standardized AATCC Spray Test Ratings Chart, which equates images of fabric saturation with a number rating, with 100 being the best, and 0 the worst.
  3. As fabrics are assigned a rating, a higher number means the more the fabric will repel water in real-world situations, such as rain or snow.

Spray Rating

Water resistance is measured in two ways. The first is the 8-inches for 10 minute test and the other is the 1 drop 3 drop.

The 8-inches for 10 minutes test essentially places an 8” high column of water (imagine a boat cover that had "drooped" down and had a standing eight inches of water at the lowest point) on a fabric for 10 minutes and at the conclusion, the amount of water that has passed through the fabric is measured and assigned a numerical value, determining how much water “leaked” thru the fabric. Most fabrics will pass this test with nothing leaking thru.

8-inches for 10 minutes test

Although at this point, national standards have been completed on the 8-inches for 10 minutes test, Marlen Textiles performs one last additional step: "The Tap." In the real world, when a boat cover is removed that has standing water on it, some of that water can be forced through the fabric simply by disturbing the cover. Marlen Textiles simulates this by "tapping" the fabric, which jostles it, at the completion of the 10 minutes. This mimics real-world behaviors. The amount of water that then passes through the fabric is measured and noted; this is also taken into consideration when testing a fabric for water resistance.

The 1 drop, 3-drop test measures the amount of pressure it will take water to pass through a particular fabric. The test raises a water column until 1 and 3 drop appears on the underside. The higher the water column, the more pressure and therefore the better water resistance.

  1. A water column is connected at its lowest point to a test fabric, and then raised to increase water pressure at the point where it meets the fabric. As the water column is raised, additional pressure is brought to bear at the point where it meets the fabric.
  2. The first measurement is noted when one water drop successfully comes through the bottom of the fabric. The second measurement is taken when 3 drops of water come through the test fabric.
  3. The higher the number, the more water resistant the fabric is, as it shows the fabric can withstand more pressure before leaking, making it more resistant to leaking.
  4. This test measures resistance to real-world situations of water “pooling” or “puddling” on a fabric.

One Drop

Drum Test

The drum test replicates real-world scenarios where large amounts of water are pooled on awnings or covers for long periods of time. The test fabric is placed over an empty drum and secured at the edges to achieve a convex effect, creating a receptacle or bag. Water is then poured into this area and a device to capture the water is placed under the fabric to collect everything that may leak through. While this test can be run indefinitely, it is typically conducted for 24 hours.

Tap Test

At the end of the 8 inch for 10 minute test, the fabric is knocked aggressively to "jostle" it. This simulates someone removing a cover that causes the fabric to move, thereby allowing more water to leak through. This is a non industry wide test Marlen Textiles does to mimic real world actions.


Click here to watch Videos of Marlen Labs' fabric testing

All fabric testing is conducted in Marlen Textiles' in-house laboratories, to industry-standard specifications.

  1. Spray Rating, AATCC-22-1974
  2. 1 drop, 3 drop, FED STD 191, Method 5516
  3. 8” for 10 Minutes, FED STD 191, Method 5514
  4. Tap, Marlen Textiles CFI in house test