In permeameters for rigid materials such as concrete, cement paste, or rock the sample is generally sealed into the test cell with a resin or with a pressurised membrane and the permeability is calculated from the total flow through the apparatus. Clearly any leakage around the edge of the sample or other inhomogeneity in the peripheral region will lead to inaccuracy in the measured permeability. This problem is particularly severe with low permeability materials such as concrete and is further exacerbated by the fact that the true permeability of concrete can vary by many orders of magnitude and there may be little information with which to assess whether particular test results are reasonable.

The divided flow permeameter offers a technique by which edge leakage and other edge effects can be assessed and several permeability results obtained from different areas of a single sample. The basic principle of this permeameter is that either the inflow or the outflow surface, or both, of the sample are divided into separate flow regions. Provided that there is no difference in pressure between the regions there should be no tendency for flow between them and the flow through each should be proportional to its area.

As the technique gives several permeability results for a single sample information about permeability variation within the sample can be obtained; for example data on microcracking, moisture distribution etc. The technique can be used with gas or liquid permeants. The divided flow permeameter system developed at King's College is inexpensive and with a simple system of ‘0’ rings a flow division head can be fitted to many conventional permeameters.