What Is Hydrostatic Head And Why Is It Important When Camping?

There are lots of things to think about when planning a camping trip. Where you’re setting up camp is obviously important, and making sure you have the right gear is key too. But there are some technical aspects to consider too, and one of these is hydrostatic head.

Hydrostatic head is the pressure measurement at which water first penetrates a fabric, such as that of a tent. Measured in millimeters of liquid, the higher the number, the greater the hydrostatic head rating. So, the higher the rating, the greater your tent’s water resistance.

Clearly, a water resistant tent is important. You don’t just need a water resistant tent for wet weather though, as condensation is also an issue to content with. Below, we’ll go into more detail about what hydrostatic head is, and why it is important for camping.

What Is Hydrostatic Head?

Hydrostatic head is essentially a measurement of how water resistant a tent (or other fabric) is. It’s measured in millimeters, and this measurement corresponds to how tall a column of water would need to be for it to penetrate the fabric. The bigger the number the more water resistant the fabric.

Today’s tent materials are much lighter, compact, durable, breathable water-resistant than those of the past. But how do you know just how good a tent is before purchasing it? Or if it is the right tent for your planned trip? The answer lies in hydrostatic head ratings. The hydrostatic head provides us with an objective measurement for comparing tents.

For example, if you live in a wet part of the country, water resistance is very important. Being able to choose between tents based on their water resistance is therefore also important, and a good way to do this is to look at hydrostatic head ratings of tents you’re considering buying.

What Is A Good Hydrostatic Head Rating?

A good hydrostatic head rating is generally 2,000+ mm. Hydrostatic head measurements generally range between 1,000 mm and 5,000 mm. Ratings will vary a lot between manufacturers, but anything above 2,000 mm is usually enough, and 3,000+ mm is ideal for those expecting very wet weather.

Other Important Tent Properties

While hydrostatic head is important for measuring the water-resistance of tent material, other factors also play a role in how comfortable and enjoyable your backpacking trip will be. These factors include tent weight, ease of setup, waterproof properties such as seams, rainfly, and openings, and ventilation.

Tent Weight

When embarking on a backpacking adventure it is important to carry all the equipment you need at the lowest weight possible. The heavier your tent, the more weight you’ll need to carry on your back while you hike. If you expect dry weather, it may be worth opting for a lighter, less waterproof tent to save your legs. But if you expect wet conditions, water resistance usually takes precedence!

Waterproof Seams

You might think that all seams are sealed well and do a great job of repelling water. Unfortunately, that is not the case. The manufacturer does not generally treat the tent seams at the factory. So, they require some attention from us when we buy a tent if we want to make them as water resistant as possible.

There are many seam sealers out on the market, and they’re usually fairly easy to use. The best tent seam sealers are:

5 Steps To Waterproof Your Tent

It is important to read the labels and instructions of any tent waterproofing products you plan to use before you begin. You will need the seam sealer, a wet rag, a dry cotton rag, and a well-ventilated space. The 5 steps to waterproof your tent are:

  1. Set up your ten fully
  2. Attach the rainfly in an upside-down position. Stretch it as you would normally and attach it to the tent.
  3. Seal all of the seams, lifting them and completely sealing both the top and bottom of them.
  4. Remember to avoid adding sealant to the zippers. This will make them sticky and hard to operate.
  5. Wait 20 minutes and repeat the process.

Seal your tent about once per year. If you use your tent often, then seal more often, and if you don’t use it that year, you probably don’t need to seal it!

What Is The Difference Between Waterproof And Water Resistant Tents?

We have all gotten caught in a rainstorm without the proper jacket. Within minutes we know whether our clothes are waterproof (we stay dry) or water-resistant (we get wet). By definition, waterproof material is impenetrable. Polypropylene tarps are waterproof. While poly tarps don’t let in any water, they are not breathable, and so not a great idea to put directly over your tent in a rainstorm.

On the other hand, water-resistant means that your tent fabric is resistant to the penetration of water into the tent, but it can let some water in, if there’s enough of it trying to get in at one time. There are a few good reasons why nearly all tents are water-resistant and not waterproof:

  1. The trade-off with weight – Water-resistant materials are generally lighter than waterproof ones.
  2. Breathability – Waterproof materials are not breathable. Water-resistant fabrics let the tent breathe and therefore allow for some ventilation. This is vital for limiting tent condensation.
  3. Quick-drying – Water-resistant materials, when breathable, dry fairly quickly.

Comparing The Water Resistance Of 3-Season And 4-Season Tents

3-Season Lightweight Tents

3-Season Ultralight Tents

Does Touching The Inside Of Your Tent Affect Your Hydrostatic Head Rating?

Touching the inside of your tent can affect hydrostatic head ratings. Touching the tent breaks the surface tension of the water. This “draws” water through the tent via capillary action. This doesn’t usually happen on modern tents with high hydrostatic head ratings.

Final Thoughts

Hydrostatic head is a measure of how water resistant your tent is. The higher the number, the more water resistant your tent material is. A hydrostatic head rating of 2,000 mm is usually good enough for most conditions, but you may need a higher rating if you expect very wet conditions on your trip.