The apparatus for removing unwanted compounds from well water, for use with a well water supply line (10), comprises: (i) a main water valve (20) for within the supply line; (ii) a water intake line (22) connected to the supply line upstream of the main valve for receiving untreated water; (iii) a water intake valve (24) in the intake line; (iv) a removal unit (26); (v) a water return line (48) connected to the water outlet which supplies water to the supply line downstream of the main valve; (vi) a water return valve (50) in the second water line; (vii) a recirculating line (52) between the water return line and the intake line, supplying water from the return line to the intake line; and (viii) a one-way valve (54) to control flow through the recirculating line and allow water from the return line into the recirculating line and the intake line for further treatment and to prevent flow from the recirculating line into the return line. The removal unit comprises: (i) a removal housing (28) defining a removal chamber (30); (ii) a water inlet (32) connected to the water intake line and the chamber for receiving untreated water from the intake line and supplying it to the chamber; (iii) a water outlet (34) connected to the chamber; (iv) an air inlet (36) connected to the chamber; (v) an air outlet (38) connected to the chamber; and (vi) removal apparatus (40) in the chamber between the air and water inlets and outlets for removing carbon dioxide (CO2), radon, volatile organics, hydrogen sulphide and methane and place them into the air supplied by the air inlet which exits through the air outlet.    USE -   Used for removing unwanted compounds from well water for use in residential or small commercial applications.    ADVANTAGE -   Total capital cost is minimised. There are bypass valves to maintain water supply during maintenance. Maintenance costs are minimised. Down time is minimised. A minimum amount of modification is required to the existing well water system. A recirculation line allows greater control of contaminant removal.