What is the waterproof difference between a tent with waterproof fabric withstanding a "2,000 mm water column", and a tent that passes the laboratory shower test of 200 litres of water per hour per sqm?
On the one hand, the waterproofness of a fabric is claimed, on the other, the waterproofness of an entire tent is proven.
Indeed, you can make a tent with multiple leaks through poorly designed seams and openings with fabric that exceeds 10,000 millimetres of water column and a perfectly waterproof tent with fabric around 1,000 millimetres.
This is what we have been checking for years by using our laboratory shower to check the watertightness of our tents (and those of others!).
Water column mm, or Schmerber mm, are therefore not a good indicator for measuring the waterproofness of a tent... they only measure the waterproofness of the fabric.
Quechua tents are designed and developed to prevent any water from passing through the seams, flaps, openings, zips, etc. Their waterproofing is tested and validated in the laboratory. The purpose of these tests is to demonstrate the waterproofing of the entire tent, not just the fabric that makes up its flysheet.
The tents are placed under a shower that pours 200 litres of water per hour per square metre for a period of 4 hours. This rain intensity corresponds to twice the intensity of a thunderstorm in Europe, for 4 hours; and our tent fabrics are 2,000 mm minimum.