We present a laboratory system to evaluate radon flux and pore water radon via automated sediment equilibration experiments. The setup includes a measured mass of sediment and water inside a gas-tight reaction flask connected in a closed loop to a radon-in-air analyzer. Diffusive fluxes are determined either from the near-linear slope of the activity versus time over the first several hours or by running the experiment longer to estimate the equilibrium concentration via a curve fitting approach. By combining the equilibrium activity with relevant physical parameters, one can also estimate the pore water concentrations.