Why you shouldn't rely on the waterproof rating of your tent

When shopping for the best tent for a UK camping trip, you'll definitely be looking for one with a high level of waterproofing. So why is it so common to STILL find water inside your tent?

Our tent tests put every tent through the worst of Britain's unpredictable weather to find out which ones you can rely on.

We sometimes find tents with high waterproofing ratings still ending up with puddles in them. That's because hydrostatic head waterproof ratings aren't the whole story when it comes to keeping water out of your tent.

Read on to find out why you should take tent waterproof ratings with a pinch of salt, tips on keeping your tent free of rain and condensation, and our top buying advice for getting a reliable, comfortable and waterproof tent.

Or head straight to our list of the top 10 best tents for a shortcut to the tents that easily repelled rain in our tests.

Hydrostatic head ratings explained

You might come across a tent with a waterproof rating of 2,000mm and assume the tent will put up with 2,000mm of rainfall before it leaks. But it doesn't quite work like that.

What it actually means: if you press a column of water 2,000mm high against the tent's canvas, the water wouldn't go through it.

These are called hydrostatic head ratings. They aren't very easy to quantify but can be understood by following a simple rule that the higher the number, the more water pressure the canvas can withstand.

However, we've found that high hydrostatic head ratings don't always equate to good waterproofing overall. 

In our tests, one tent might be bone dry at the end of testing while the other has puddle inside, despite them having similarly high hydrostatic head ratings.

This is because most leaks in tents don't come through the canvas: they come in through the seams and zips. If the seams and zips haven't been stitched and sealed together securely, water will leak into the tent regardless of how repellent the canvas is.

If there's a lot of water coming in at a certain point along a seam or near the door of your tent, it's likely to be a problem with the stitching and should be covered by your tent's warranty.

Give the waterproofing on your tent a test drive before camping with our pick of the best garden hoses.

How to keep your tent as dry as possible

• Open the vents Even in dry conditions there's plenty of moisture in the air, so it's a good idea to keep your vents open where possible during your camping trip. Good air circulation will help moisture escape outside.
• Avoid touching the walls and ceiling Applying pressure to the canvas when the tent is pitched risks breaking the surface tension between water on the outside and the canvas underneath, which will funnel that water through the canvas at the point of contact.
• Watch out for doors that open inwards If it has rained recently, lots of water droplets will sit on the door. If it opens inwards, all that water will run off the door into your tent. Take care to hold the door and pull it outwards as you're unzipping it.
• Keep wet gear out of the bedroom Damp clothes bring unwanted moisture into the tent, and the waterproof shell means moisture won't have anywhere to go as your gear dries. It will likely condense on the ceiling and make your sleeping area damp.
• Open doors and windows for a couple of hours every day As mentioned above, air circulation is key to keeping moisture out of your tent. It's a good idea to prop the doors and windows open for a couple of hours a day to give the circulation a boost.

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Is my tent leaking or is it condensation?

It's common to wake up in the morning to see droplets of water sitting on the ceiling of your tent. This is most likely condensation rather than a leak, and there's little you can do to eliminate it from your camping experience.

Lots of moisture floats around in the air we breathe, and the tent's waterproof barrier traps the moisture.

The air inside the tent also tends to be warmer than the canvas, causing the moisture to condense into liquid when it touches the ceiling.

Campers inside a tent are the biggest cause of condensation. Over the course of one night's sleep a person can breathe out as much as one pint of water into the air. Even with good air circulation it's difficult for all of that moisture to escape your tent.

As advised above, taking steps to keep your tent as ventilated as possible will help to reduce condensation. 

Don't hurry back to the shop to return your tent if you do find the ceiling a little damp, though. Water coming in from a small single point or consistent heavy leaking is likely to be a leak, but damp or water droplets in a patch on the ceiling is probably just condensation and nothing to worry about.

Listen: A beginner's guide to camping

Hear our camping expert explain how hydrostatic head ratings in tents work, and the key things you should be looking for when shopping for tents that'll keep you dry.