A wall is wet and you don't know why. To find the cause and location of the leak, the wall probably will have to be tested. Contractors should know what types of tests are available. Here are a few nondestructive tests and how they work. THE TUBE TEST Developed by the European organization RILEM, the tube test evaluates the wall's permeability. The tube has a flat circular brim at the bottom that is attached to the substrate with putty. Water is then added to the graduated tube. The water level is checked and the readings are plotted on a graph comparing the volume of water absorbed with time required to absorb it. THE SPRAY TEST A garden hose and calibrated nozzle are needed for the spray test. To isolate points of water infiltration, a technician wets specific wall areas to see where leaks occur. THE PERMEABILITY TEST A field technician drives two bolts into a bed joint and installs clamps that support a device on the wall. Next, water is pumped into the device. Then the water is forced into the wall. The time required to force the know volume of water into the wall is recorded. MODIFIED ASTM E 514 FIELD TEST ASTM E 514, Test Method for Water Permeance of Masonry is a laboratory test modified for use on existing walls. Water is sprayed into a chamber mounted on the wall and the amount of water leaking into the wall is measured. THE DRAINAGE TEST The drainage test can evaluate the drainage capacity of 40 feet of masonry cavity and flashing at one time. Through holes drilled in the exterior brick, water trickles into the cavity at rates based upon water penetration measured by a modified ASTM E 514 test procedure.