Pressure filtering systems use compressed nitrogen or air to force the water out of a reservoir through the filter. Pressure filter units are usable for filtering moderate volumes of water without too much filter clogging material present. For a safety standpoint the pressure on these systems should be kept as low as possible and should not exceed 30 psi. Pressure filter units are not recommended for general use unless the type and design is proven to be safe and reliable. Units that are used must have approved safety devices to prevent over pressurization and reliable regulation of the amount of pressure applied to the unit.
Several types are available from the major filter manufactures.
You should check with your Regional Safety Officer before purchasing any pressure units. The Ohio District has designed a PVC low pressure unit using a membrane safety valve and hand squeeze bulb as a pressure source. This unit has been approved for general field use. At present, though there is no commercial source from which the unit may be purchased. A description and plans of the unit can be obtained from the Ohio District.