Drenvsubir application is develop in Borland Delphi Pascal v7.0 programming system and is created for calculating sizes specific to drainage system such as: determination of the distance between drains with the verification of functioning at subirrigation. DrenVSubIR calculation program consist of three modules, the first of calculation of the distance between drains wires in permanent regime, the second for verifying conventional drainage reversibility in controlled drainage and subirrigation and the third for technical and economic calculation of a hectare of drainage field. The module for sizing distance between drains in permanent regime used Ernst relation, completed by David I. (1982), which submits adding in the composition of loss of hydraulic load due to the resistance at the water entering drain-filter complex, value calculated with the help of some coefficients experimentally determined. Verification reversibility module of the drainage projected in the subirrigation of the DrenVSubIR program uses David Equation, after calculating the distance between L drain and the values determined at the projection of distance between drains. The technical-economic calculation module uses all of the initially introduced dates giving the cost for a hectare of field.