The present invention generally relates to devices able to purify fluids electrically that are contained within pressure vessels, as well as to methods of manufacture and use thereof. Liquids or other fluids to be purified enter the purification device and, under the influence of an electric field, are treated to produce an ion-depleted liquid. Species from the entering liquids are collected to produce an ion-concentrated liquid. Increasing the exterior pressure on the device may reduce the pressure difference between the interior of the device and the exterior, which may reduce manufacturing costs or simplify construction.