Reverse osmosis purification system

A method for providing potable water on demand from an impure aqueous source using a reverse osmosis water purification unit without any accumulation reservoir, which method comprises:

• sensing the opening of tap means through which potable water is to be withdrawn,
• in response to said sensing, actuating a motor driven pump means having an inlet and a discharge, which pump means inlet is connected to the impure aqueous source,
• discharging a feed stream of impure water from said pump means under pressure to a reverse osmosis purification unit having a purified water outlet and a brine outlet and thereby causing a stream of purified water to flow from said purified water outlet to said tap means and an aqueous concentrate to flow from said brine outlet,
• recycling at least some aqueous concentrate exiting from said brine outlet of said purification unit back to said pump means,
• further sensing when said tap means is closed following withdrawal of water therethrough and thereafter recirculating said stream of purified water to mix with water flowing from the impure aqueous source and provide a composite liquid stream flowing to said pump means,
• continuing said recirculation until the concentration of dissolved salts and minerals in said feed stream flowing to said purification unit from said pump means reaches a predetermined low level,
• determining said predetermined low level of dissolved salts in said composite stream by sensing when the level of dissolved salts and minerals in said aqueous concentrate flowing from said brine outlet falls below a desired level, and
• halting operation of said pump means when said desired level is reached.

A method for intermittently providing potable water on demand for domestic use from an impure aqueous source using a reverse osmosis water purification unit without any accumulation reservoir, which method comprises:

• sensing the opening of tap means through which potable water is to be withdrawn,
• in response to said sensing, actuating a motor driven pump having an inlet and a discharge, which pump inlet is connected to the impure aqueous source,
• discharging a feed stream of impure water from said pump under pressure to a reverse osmosis purification unit having a purified water outlet and a brine outlet and thereby causing a stream of purified water to flow from said purified water outlet to said tap means and an aqueous concentrate to flow from said brine outlet,
• recycling at least some aqueous concentrate exiting from said brine outlet of said purification unit back to said pump,
• further sensing when said tap means is closed following withdrawal of water therethrough and thereafter opening a valve to recirculate said stream of purified water to mix with water flowing from the impure aqueous source and with the concentrate being recycled to thus provide a composite liquid stream flowing to said pump,
• continuing said recirculation of purified water until the concentration of dissolved salts and minerals in said feed stream flowing to said purification unit from said pump reaches a predetermined low level,
• determining said predetermined low level of dissolved salts in said composite stream by sensing when the level of dissolved salts and minerals in said aqueous concentrate flowing from said brine outlet falls below a desired level, and
• halting operation of said pump and closing said valve when said desired level is reached.