Have you ever planned a nice relaxing camping journey with your friends, set up your tent and fell asleep, only to be woken up with leaking rain and puddles in the middle of the night?
Ughh nightmare…
No one wants to think about being stranded in a tent in the middle of nowhere (unless wild camping is your thing) whilst it’s pouring down with rain but this can be a very real reality and it is important to prepare for the worst.
That is why you need to make sure that before you start your camping journey, your tent will be durable and waterproof enough to survive the coming weather. This becomes doubly important if you are planning to camp in a place where heavy rainfall is quite common. How does one determine whether or not a tent is waterproof?
Well in the camping world, waterproofing is determined by the hydrostatic head rating, which you will usually find indicated when you go to buy a tent to camp in.
What exactly is a hydrostatic head rating (HH)?
Not all tents are made equally, but some are better equipped to deal with rain than others. The HH rating or hydrostatic head (also known as the water column) rating can be a key deciding factor of a tents resistance to rain and its waterproofing capabilities.
The ‘water column test’ is a method of testing the waterproofing of a material. This is done with a lab test where a cylindrical tube with a diameter of 2.5 cm is placed on the material and is then filled up with water. A material’s waterproofing rating will determine the level of water pressure it can handle without leaking through.
For example, if a tent material can handle 2cm of water before leaking through, then it will be given a rating of 2000mm.
You might be asking yourself, what HH rating should I be looking for when buying a new tent?
Here are some important Hydrostatic Head brackets for your information:
| Waterproof Rating (mm) | Level of Protection Provided | What does it protect you from? |
| 0 – 1,000 mm | No protection – Some protection from moisture | Light rain, dry snow, no pressure |
| 1,000mm – 2,000 mm | Waterproof and rainproof under a light amount of pressure | Light rain, moderate snow, light pressure |
| 2,000mm – 3,000 mm | Waterproof and rainproof under a medium amount of pressure | Moderate rain, moderate snow, medium pressure |
| 3,000mm – 5,000 mm | Waterproof and rainproof under high amounts of pressure | Heavy rain, heavy snow, moderate pressure |
| 5,000 mm + | Waterproof and rainproof under very high amounts of pressure | Very heavy rain, heavy wet snow, high pressure |
How much hydrostatic head do I need?
Whilst this is great information to know when it comes to tents, the low – mid-range tents will come under the 2 – 3,000mm brackets whereas some high-quality tents will come under the 3, 000mm – 5,000mm brackets.
What does that mean?
It simply means that most tents are not meant to be soaked and put under a huge amount of water pressure. Most are built to get you through some bad weather at least but it is advisable not to go camping if the weather will be very bad. Although, we doubt that you’d plan to camp in a storm anyway…
How is the hydrostatic head rating calculated?
When manufacturers want to convey how waterproof and breathable their tents are, they tend to use 2 key metrics to describe this. These are in millimetres (mm) and grams (g) respectively. Let’s run through how waterproofing might be calculated using these two metrics.
Millimetres:
This metric is usually used to describe how waterproof a piece of fabric is. For example, if a piece of fabric is rated with a HH rating of 10,000mm, it means that if you place this fabric under a tube and fill it with water to a height of 10,000mm, only then would water begin to leak through. The higher this rating, the more waterproof a piece of fabric is going to be.
Grams:
This number measures how breathable a piece of fabric is and refers to the grams (g) of water vapour that is able to pass through a square metre (m2) of fabric over 24 hours. For example, with a fabric that has a rating of 15,000 grams, it would take 15kg worth of water vapour to pass through it. As with the mm, the higher this number, the more breathable this fabric is going to be.
How do companies determine waterproofing ratings?
Usually, waterproofing tests are conducted by manufacturer or fabric producers in-house or by utilising an external independent lab. One of the most common tests that are used to determine waterproof ratings is the ‘static column test’ also known as the ‘hydrostatic head test’. If you want a deeper look into how this test is carried out, watch the video below:
You may not know this, but there are a few different ways in which you can test the water rating and each of these may produce slightly different results. That could mean that the same piece of fabric could end up having different waterproof ratings depending on the waterproofing test that was conducted.
Hopefully, now you have a better understanding of what all those HH numbers mean on your tent and can better determine how well it will perform in different weather conditions. If you want more information about your tent check out our blog and follow our Pinterest account for more motivation and cool camping pictures to help you decide.