pneumatic water supply

a water supply system within a commercial building, at a single family residence or farm that is continuously pressurized by a water tank with an air chamber.

In tall commercial buildings water pressure on the higher floors is less than those on the lower floors. This is often corrected using gravity tanks installed on the top of the building. A pneumatic water system eliminates the need for a roof-top tank.

Older pneumatic systems consisted of a booster pump supply a pressurized water tank. The tank held a supply of water and was partly charged with air. The air in the tank acts as a cushion that can exert or absorb pressure as required. An air compressor was used to maintain the air charge in the tank.

The older system has been replaced with a booster pump system and a water tank with a bladder. The older tanks relied on a charge of air in the tank. The bladder tank eliminates the air-to-water surface in the tank causing regular air loss (water logging). The water in the tank is contained in a flexible bladder that fills the bottom two-thirds of the tank. Some tanks are designed with a diaphragm that floats or is fixed to separate the water from the air.

Single-family homes and farms with private water wells often use a hydro-pneumatic tank to maintain water pressure. The well pump runs less and pressure surges are reduced when the pump starts. The smaller tanks in this case may also be called “captive air tanks”, “bag tanks” or “bladder tanks”.

Also called a "hydro-pneumatic water supply" or "hyrdro-pneumatic water system".