When shopping for outdoor gear, especially tents and tarps, you'll often come across the term "hydrostatic head" or "HH." This technical specification is crucial for understanding how waterproof a fabric is. In this article, we'll demystify what hydrostatic head means and how it affects the performance of your tents and tarps.
What is Hydrostatic Head?
Hydrostatic head is a measurement used to determine the waterproofness of a fabric. It is expressed in millimetres (mm) and indicates the amount of water pressure a fabric can withstand before it starts to leak. The higher the number, the more waterproof the fabric is.
How is Hydrostatic Head Measured?
The hydrostatic head rating is determined through a standardised test. During this test, a column of water is placed on top of the fabric sample. The height of the water column is gradually increased until water begins to penetrate the fabric. The height of the column at which water starts to seep through is measured in millimetres and represents the hydrostatic head.
For example, if a fabric has a hydrostatic head of 3000 mm, it means the fabric can withstand a column of water that is 3000 mm (or 3 meters) high before it starts to leak.
What Hydrostatic Head Ratings Mean for Waterproofing
Here’s a general guide to what different hydrostatic head ratings mean for the waterproofing of tents and tarps:
1000 mm – 1500 mm
This is considered the minimum level of waterproofing. It can handle light rain but may not be sufficient in prolonged or heavy downpours.
1500 mm – 3000 mm
Suitable for moderate rain. Most quality camping tents and tarps fall within this range, offering good protection against typical weather conditions.
3000 mm – 5000 mm
Offers excellent waterproofing, suitable for heavy rain and more severe weather conditions. High-quality expedition tents often have ratings in this range.
5000 mm and above
Extremely waterproof, ideal for extreme weather conditions and prolonged exposure to heavy rain. This level of waterproofing is typically found in specialised gear designed for the harshest environments.
Choosing the Right Hydrostatic Head for Your Needs
When selecting a tent or tarp, consider the typical weather conditions you'll encounter and how long you expect the gear to be exposed to rain. Here are a few tips:
Casual Camping: If you're camping in areas with mild to moderate weather, a tent with a hydrostatic head of 1500 mm to 2000 mm should suffice.
Frequent Campers and Hikers: For those who camp more frequently or in more variable weather, look for tents and tarps with a hydrostatic head of at least 3000 mm.
Expedition and Extreme Conditions: If you're planning an expedition or expect to camp in harsh, rainy environments, choose gear with a hydrostatic head of 5000 mm or more.
Other Factors Affecting Waterproofing
While hydrostatic head is a crucial measure of waterproofing, it's not the only factor to consider:
Seams: Ensure that the seams of the tent or tarp are sealed or taped, as these are common points where water can leak through.
Fabric Quality: The overall quality and durability of the fabric also play a role in waterproofing. Higher quality materials generally provide better performance and longevity.
Design: The design of the tent or tarp, including its shape and the way it handles water runoff, can also impact its waterproofing effectiveness.
Conclusion
Understanding hydrostatic head is essential for choosing the right tent or tarp for your outdoor adventures. By paying attention to the HH rating, alongside other factors like seam sealing and fabric quality, you can ensure you stay dry and comfortable, no matter the weather conditions. Whether you're a casual camper or an extreme adventurer, knowing how to evaluate waterproofing will help you make informed decisions and enhance your outdoor experience.
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