{"id":11258,"date":"2026-08-26T00:26:59","date_gmt":"2026-08-25T16:26:59","guid":{"rendered":"https:\/\/tiiocti.com\/hydrostatic-head-testing-waterproof-bag-claims\/"},"modified":"2026-08-26T00:26:59","modified_gmt":"2026-08-25T16:26:59","slug":"hydrostatic-head-testing-waterproof-bag-claims","status":"publish","type":"post","link":"https:\/\/tiiocti.com\/ru\/hydrostatic-head-testing-waterproof-bag-claims\/","title":{"rendered":"Hydrostatic Head Testing: The Standard Behind Waterproof Bag Claims"},"content":{"rendered":"

Hydrostatic Head Testing: The Standard Behind Waterproof Bag Claims<\/h1>\n

A bag that claims to be waterproof has to spend its claim somewhere real, and for a fabric the measure is the hydrostatic head. Hydrostatic head testing measures how much water pressure a fabric resists before it leaks, and it is the number behind a “water resistant” or a “waterproof” claim. This guide explains what the test measures, what a result means in practical terms for a bag, and the question to ask a factory before you trust the label.<\/p>\n

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Verify the waterproof claim on the products<\/a> range, with the fabric head and the seam construction checked.<\/p>\n

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What the test measures<\/h2>\n

Hydrostatic head testing measures the water column height a fabric withstands before water passes through, expressed in millimetres. A fabric is clamped and a column of water is applied from one side, and the height at which the first droplet appears on the other side is the hydrostatic head. A higher number means the fabric resists a taller column of water, so it better resists rain and standing water. The result is a measure of the fabric’s resistance, not of the bag’s seams, because a seam is the point where water gets in even on a high-head fabric.<\/p>\n

What a result means for a bag<\/h2>\n

A low hydrostatic head, in the region of a few hundred millimetres, is enough for a light shower and a splash, while a higher figure is what a serious waterproof bag uses for a longer exposure or heavier rain. The number alone does not make a bag waterproof; the seams have to be welded or taped, and the closure has to be sealed, because water will enter at a seam or a zip long before the fabric leaks. So a bag manufacturer’s claim is the combination of the fabric head and the construction, and you have to ask for both rather than the fabric number on its own.<\/p>\n

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The question to ask a factory<\/h2>\n

Ask for the hydrostatic head of the fabric used, the test method, and whether the seams are welded or taped. Ask for a lab report rather than a verbal figure, and confirm the head is measured on the production fabric, not on a hand-picked sample. If the bag is sold to a user who expects it to keep a load dry in the rain, the seams and the closure carry more of the real-world result than the fabric number does. The standards that set the hydrostatic head test and the water-resistance measurement are published by the ASTM<\/a> standards body, which is where the test method and the reporting convention come from.<\/p>\n

Need a verified waterproof bag? Send Tiiocti your exposure level for a tested fabric and seam spec.<\/p>\n

Related reading<\/h2>\n

See the range on products<\/a> and the QC testing on quality<\/a>.<\/p>\n

FAQ<\/h2>\n

What is hydrostatic head testing?<\/h3>\n

It measures the water column height a fabric resists before water passes through, in millimetres. A higher number means the fabric better resists rain and standing water.<\/p>\n

Does a high hydrostatic head make a bag waterproof?<\/h3>\n

Not on its own. The seams have to be welded or taped and the closure sealed, because water enters at a seam or a zip long before the fabric leaks, so the fabric head is only half the claim.<\/p>\n

What should I ask a factory about a waterproof claim?<\/h3>\n

The hydrostatic head of the fabric, the test method, whether the seams are welded or taped, and a lab report on the production fabric rather than a hand-picked sample.<\/p>\n

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