When venturing into the great outdoors, understanding the term ‘Hydrostatic Head’ (HH) is crucial for selecting the right gear. This guide will explain what hydrostatic head is, its importance in outdoor equipment, and how to interpret these ratings to ensure you stay dry and comfortable in any weather.
What is Hydrostatic Head?
Hydrostatic Head is a measurement used to determine how waterproof a fabric is. It indicates how tall a column of water the material can withstand before water starts to seep through. For example, a fabric with a hydrostatic head of 3000mm can resist a 3-meter column of water. The higher the HH rating, the more water-resistant the fabric.
Ideal Hydrostatic Head Ratings for Tents:
- Light Showers: For regions with light rainfall, a tent with a minimum HH of 1000mm is usually sufficient.
- Moderate to Heavy Rain: In areas prone to heavier rain, look for tents with HH ratings of 3000mm to 5000mm.
- Extreme Conditions: For harsh weather, including heavy snow or torrential rain, tents with HH ratings of 5000mm to 10000mm are recommended.
Hydrostatic Head in Jackets and Rainwear:
- General Waterproofing: In the UK, a fabric can be labeled waterproof if it has an HH of 1500mm. However, most quality jackets exceed this, with ratings ranging from 10,000mm to 30,000mm.
- Activity-Specific Needs: For active wear like cycling or hiking, where breathability is also crucial, a lower HH rating might be more suitable to balance waterproofing with ventilation.
Groundsheets and Hydrostatic Head:
Groundsheets typically have higher HH ratings than tent fabric, often exceeding 10,000mm. This is due to the direct contact with wet ground and the pressure exerted by occupants and gear.
Hydrostatic Head in Other Outdoor Products:
- Tarps and Bivy Bags: These items benefit from high HH ratings to ensure dryness under various conditions.
- Drybags: Lighter drybags may have lower HH ratings but are suitable for general use. For activities like sea kayaking, opt for heavier-duty drybags with higher HH ratings.
Factors Affecting Real-World Waterproofing:
While HH is a key indicator of water resistance, other factors also play a role in a product’s overall waterproofing capability:
- Seam Construction: Taped or sealed seams can prevent water from seeping through stitch lines.
- Design Features: Elements like hood design and zipper covers can enhance a jacket’s ability to keep out rain.
- Material Durability: The fabric’s ability to withstand wear and tear, especially in clothing, affects its long-term waterproofing.
Understanding hydrostatic head ratings is essential for choosing the right outdoor gear. Whether you’re selecting a tent, jacket, or groundsheet, consider both the HH rating and other design features to ensure optimal performance in your specific outdoor environment. With this knowledge, you can confidently prepare for your next adventure, knowing your gear will keep you dry and comfortable, no matter the weather.
