Waterproof tents · The basics
What Is a Hydrostatic Head Rating for Tents? (REAL Test Results!)
The mm figure that says how much water your tent fabric holds before it leaks, and why my 5,000mm tent leaked while a 1,200mm one didn’t.
- 1,000mm the waterproof line
- 1,000-5,000mm typical range
- 4 brands rain-tested
- $0 sponsored
- ~6 min read
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The short answer
Millimetres of water held
Clamp the fabric under a rising water column; the pressure where it leaks is the rating.
What it is ↓At least 1,000mm
Below that it’s water-resistant, not waterproof. Most tents I own run 1,000-5,000mm.
The 1,000mm line ↓The number alone proves nothing
My 5,000mm Zion leaked in 2 hours because the tub floor was only 5 inches.
What else matters ↓A hydrostatic head rating tells you how much water a tent’s fabric can hold before it starts leaking, measured in millimetres. Higher means more waterproof fabric. It isn’t the whole story, which is the part most people miss.
Part 1 of 7
What the number actually means
Most of the waterproof camping tents I’ve tested rate between 1,000mm and 5,000mm, and that has been plenty for my trips. I’ve seen tents advertised up to 10,000mm but never tested one. The rating isn’t tent-specific either. Waterproof jackets and ponchos carry it too, and those go up to 30,000mm.
Part 2 of 7
How it is measured
Not something you or I can do at home. It’s a lab test, on a specialised machine, standardised across manufacturers so the numbers are comparable. The fabric is clamped against a water column, the pressure rises until water comes through, and a manometer records the point of leakage.
1,000mmmeans the fabric holds a 1,000mm water column, and leaks at 1,500mm
Part 3 of 7
The 1,000mm line
My ruleFor a tent to count as waterproof, it needs a hydrostatic head rating of at least 1,000mm. That figure kept me dry through light rain and several hours of heavy rain. Anything below it’s water-resistant, not waterproof.
| Brand | HH rating | Heavy rain |
|---|---|---|
| Ozark Trail | None | 0 minutes |
| Coleman | 450mm | 30-60 minutes |
| Core Equipment | 600mm | 30-60 minutes |
| The North Face | 1,200-1,500mm | 3 days |
So Coleman, Core and Ozark Trail tents aren’t waterproof, only water-resistant, and they will not hold out heavy rain for long. If you expect several wet days, go for 2,000mm and up. Those are the ones in my best waterproof tents round-up.
Part 4 of 7
How coatings create the rating
Manufacturers coat the floor, body and rainfly to lift the rating. Polyurethane goes on polyester tents, silicone on nylon. The coating fills the gaps between the threads, which is what pushes the number up.
Part 5 of 7
Why a higher rating is not automatically better
- WeightThicker coating, heavier fabric. Ultralight backpackers often take a satisfactory 1,200mm instead: dry through hours of heavy rain, without the weight.
- RigidityThicker coating also stiffens the fabric, and at some point that raises the chance of tearing in strong wind. Manufacturers have to balance the two, which is why most sit at 1,000-2,000mm rather than reaching for 10,000mm.
- It only covers the fabricA great rating on a tent whose other features aren’t properly waterproofed still leaks. That is the next section.
Part 6 of 7
The four things that matter just as much
1. Stitching
Every stitch is a hole in your tent. Higher-end brands put smaller, more consistent holes in; budget brands make bigger ones, and bigger holes let more water through.
2. Seam taping
Big holes or small, every seam has to be sealed with tape. You can see it: a strip of plastic-like tape running over the seam. My budget tents, such as Core, Coleman and Ozark Trail, don’t always have it, and the un-taped seams are always the first to leak.
3. Zipper protection
Second place to leak, in my experience. Most of my tents have a zipper cover over the track (you will also hear these called storm flaps or rain flaps), and some have one on the inside too, to catch whatever gets past.
My ruleSet the zippers as high up the tent as you can rather than down low.
4. Tub floor height
My Zion had a 5,000mm floor rating and a 5-inch tub floor. In heavy rain the drops bounced off the ground, cleared the lip and splashed straight in. Two hours later the whole edge of the tent was water and mud.
My adviceThe hydrostatic head rating isn’t the be-all and end-all. Stitching, taping, zippers and tub height decide just as much of whether you wake up dry.
Part 7 of 7
Keeping the rating you paid for
Hydrostatic head performance isn’t a one-time setup. Everything deteriorates, canvas included. My routine:
- On every tripA ground tarp under the tent floor. A cheap one from Amazon is enough.
- After a long tripClean with a non-abrasive sponge, cold water and non-detergent soap. No machine washing, no machine drying, no household cleaners.
- Every 1-2 yearsPatch any tears, reseal the seams with the sealant I use on polyester, then renew the fly’s waterproofing with the spray I use. More often if you camp a lot.
The bottom line
Hydrostatic head is millimetres of water the fabric holds before it leaks. 1,000mm is the waterproof line; most good tents sit at 1,000-5,000mm. But the number only covers the fabric. Stitching, seam tape, zipper covers and tub floor height decide the rest.
Quick questions
FAQ
What is a good hydrostatic head rating for a tent?
At least 1,000mm. Below that it’s water-resistant, not waterproof. Most of the waterproof tents I’ve tested rate 1,000mm to 5,000mm.
Do all waterproof tents have a hydrostatic head rating?
No. Some tents are genuinely waterproof without a published figure, and canvas tents aren’t usually tested for it at all.
Can a tent with a high hydrostatic head rating still leak?
Yes. My Hyke and Byke Zion 2 has a 5,000mm rainfly and floor and still let water in after 2 hours, because the tub floor was only 5 inches tall.
Keep going
Where to next
The brand check
Are Ozark Trail Tents Waterproof?
What happens when a brand publishes no rating at all.
Every rating, rain timing and photo here is from tents I bought myself and tested in my own yard.
