fig1 depicts a refrigerator door 1 , shown partially in vertical section . in the door there is provided a conventional compartment 2 open towards the outside and usable by the user to fill any container , for example a glass , with ice via a conventional dispenser for that purpose , or with cooled water which , according to the invention can be carbonated or still . the water is dispensed via a nozzle 4 intercepted by a valve 5 conventionally operated by the user who for this purpose acts on a dispensing handgrip operationally connected to the valve . the nozzle 4 , valve 5 and handgrip 6 form a dispenser and are situated at the lower end of a water container , of given capacity , 7 mounted in a tubular seat 8 , which extends into the compartment 2 and forms part of the lining of this compartment 2 . a chamber 10 of the compartment 2 ( compartment to which access can be gained from the outside or from the inside of the door and which is closed by a shutter , not shown ) removably houses a co 2 cylinder , indicated by 11 and connectable to the container 7 to carbonate the water quantity contained therein , as described hereinafter with particular reference to fig2 . this latter figure shows a more detailed construction of that already described . in fig2 equal or corresponding parts carry the same reference numerals as already used . the co 2 cylinder is screwed or tightly pressed into a port 20 forming part of a support piece 21 fixed to the roof 22 of the compartment 2 . the cylinder 11 is closed by a seal 23 that is perforated by a needle valve 24 mounted in the support piece 21 and located at the entry to a conduit 25 that extends into the support piece 21 and to which a solenoid valve 26 is connected via a pipe 27 . the exit of the solenoid valve 21 is connected via a pipe 28 to an inlet port 29 present in a cover 30 fixed in any known manner to the support piece 21 . the cover 30 forms the seal for the water container 7 ( which defines the carbonation environment ) that , in this example , is integral with the support piece 21 . the cover presents a nozzle 31 that passes through the cover , and at one end is connected to a conduit 32 for feeding water , for example tap water . at its other end the nozzle 31 is provided with a controlled valve 32 a . a pressure gauge 33 can also be connected to the cover . the cover 30 also carries : a conventional level sensor 34 which extends into the container 7 , and a safety ( overpressure ) valve 35 which acts on an electrical microswitch controlling a carbonated water indicator lamp ( not visible ) indicating that carbonation has taken place . although not shown , there is also provided a pushbutton , which by operating ( in the sense of opening ) the solenoid valve 26 connects the container 7 filled with water to the cylinder 11 for carbonating this water . initially the container is empty . the level sensor 34 senses this situation and causes water to enter the container through the electrically operated valve 32 a or alternatively through a solenoid valve , not shown , positioned in the conduit 32 . the cooled still water is hence fed into the container 7 . when a predetermined water level is reached , the level sensor 34 halts the feed of water ( by acting on the valve 32 a or on the alternative valve ) and lights an indicator lamp that warns the user that the desired water level has been attained . the still water can however be withdrawn continuously even if the desired level has not been reached and the relative indicator lamp is not lit . withdrawal is achieved in conventional manner by acting on the nozzle 4 , valve 5 and handgrip 6 . when the level indicator lamp is lit , the user can , if desired , initiate the carbonation phase by pressing a pushbutton ( not shown ) which activates the solenoid valve 26 , enabling the co 2 to flow from the cylinder 11 to the container 7 and to carbonate the water contained therein . as already stated , the container 7 presents a safety and overpressure valve 35 provided with a electrical switch which when the required pressure has been attained in the container 7 closes the solenoid valve 26 and lights the indicator lamp to advise the user that the now carbonated water is ready to be drawn off . in the case of operating anomalies , for example overpressure , the safety valve 35 opens to discharge the excess co 2 into the atmosphere and at the same time closes the solenoid valve 26 to prevent the danger of explosion of the container 7 . the following advantages derive from the invention : the user no longer has to physically purchase large quantities of still or carbonated water , transport it and then store it in the home ; this signifies a saving of time and fatigue ; in addition empty bottles do not have to be retained for their recycling , there is less refuse and from an economical viewpoint there is a saving in the cost of the water , in addition to having it always available when required by the user . the reference numeral 50 indicates a pressure sensor ( pressure switch ) that measures the pressure of the cylinder 11 and acts on an indicator lamp ( not shown ) to warn the user that the cylinder is empty .