The Water Column in Horse Blankets: Everything You Need to Know
The water column is one of the most important, yet also most misunderstood criteria when it comes to rain sheets. In this article, you’ll learn what the water column really means, how it is measured, and why a very high water column is not always the best choice for your horse.
What Does “Water Column” Actually Mean?
The water column indicates how waterproof a material is. It is measured in millimeters (mm) and describes the pressure a fabric can withstand before water penetrates. Simply put: the higher the number, the more water pressure the material can resist.
An example:
- 3,000 mm water column means that the fabric can withstand water pressure equivalent to a 3-meter-high column of water.
- 10,000 mm means the equivalent of 10 meters.
How Is the Water Column Measured?
To reliably determine the water column, special laboratory tests are carried out. A piece of the fabric used for the rain sheet is clamped into a testing device. This device is designed to apply water onto the surface of the material in a controlled manner. Step by step, the water pressure increases – as if a higher and higher “water column” were building up on the fabric.
The crucial point is reached when the first drops penetrate the material. At exactly this point, the value is recorded: it indicates the water pressure in millimeters that the fabric withstood before leaking. A test result of 3,000 mm therefore means that the fabric resisted a water column three meters high before water seeped through.
What Water Column Is Sensible for Horse Blankets?
For horses, the water column plays an important role – but it’s by no means the only criterion. In practice, it has been shown that a blanket with a water column of 3,000 to 5,000 mm is more than sufficient to reliably keep your horse dry during normal rain. These values provide solid protection without making the material unnecessarily thick or stiff.
In cases of heavy rain or prolonged periods of wet weather, a somewhat higher water column may seem beneficial. However, this is where the crucial drawback comes in: the higher the water column, the less breathable the material usually is. This means that while rain can’t get in from the outside, moisture and sweat from inside also escape less effectively.
The result can be:
Your horse may stay dry on the outside, but it can start sweating under the blanket because air circulation is reduced – leading to an unpleasant “sauna effect.”Therefore, the rule of thumb is: The optimal water column is always a compromise between protection and breathability. For most situations, 3,000–5,000 mm is the best choice – anything beyond that is usually only necessary in extreme conditions.