# What is the Karsten Tube Test?
**The Karsten tube test (also called the pipe method or RILEM tube test) is a non-destructive field method used to measure the water absorption rate of facade materials. A small graduated glass tube is attached to the building surface with putty, filled with water, and the rate at which the water level drops is recorded — indicating how readily the material absorbs moisture.**
## How the test works
1. A graduated glass tube (resembling a small funnel or pipe bent at 90 degrees) is sealed against the facade surface using a ring of non-porous putty or silicone.
2. The tube is filled with water to a marked level, applying a defined hydrostatic head (typically 10 cm of water column).
3. At regular intervals (e.g., every 5 minutes over a 15-minute period), the water level is read from the graduated scale.
4. The volume of water absorbed per unit area per unit time is calculated and compared against reference values.
## Interpretation of results
High absorption rates indicate porous, unprotected, or deteriorated surfaces that are vulnerable to moisture ingress, frost damage, and efflorescence. Low or zero absorption suggests effective water-repellent treatment or dense, well-maintained material.
## Standards and references
The test is described in RILEM Test Method II.4 and is widely used across Europe. It provides a quick, inexpensive assessment without damaging the facade.
## Advantages
– Non-destructive and portable
– Provides immediate on-site results
– Requires no electricity or expensive equipment
– Suitable for vertical and overhead surfaces
## Applications
– Assessing the effectiveness of water-repellent impregnation treatments
– Diagnosing moisture problems in existing facades
– Quality control after restoration or repointing work
– Comparing absorption rates of different masonry units or renders
– Pre-purchase building condition surveys
## Related terms
– Water absorption
– Hydrophobic impregnation
– Capillary suction
– Moisture survey
– RILEM test method
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