Provided herein are water distribution systems and methods of operating water distribution systems that include a heat pump transferring heat between a first water stream dispensed into a space and a second water stream collected after use of the first water stream in the space. The heat pump can efficiently and effectively raise the temperature of the first water stream to a comfortable level for a user. In some embodiments, the first water stream may be further conditioned and/or processed downstream from the heat pump prior to being dispensed, e.g., using a mixing valve, a water storage tank, and/or a thermal storage device. In some embodiments, one or more operating parameters of the heat pump may be controlled according to a desired temperature of the first water stream being dispensed into the space.

A drain system for recovering thermal energy from a flow of shower or faucet greywater. The drain system comprises: a drain inlet for receiving greywater; a heat exchanger configured to heat a flow of incoming cold water with the greywater flowing from a grey water inlet to a grey water outlet; and a water level control pipe portion arranged downstream of the grey water outlet. The drain system further comprises a downcomer arranged downstream of the water level control pipe portion. The downcomer comprises a contraction for increasing the flowrate of greywater from the grey water inlet to the grey water outlet.

A heat recovery system (1) suitable for recovering a part of the heat energy from hot water, water from bathing and washing facilities, which is energy that is usually lost when the water is drained into the sewer is provided. This energy can be recovered and reused to heat mains water to be immediately available for use.

A grey water heat recovery apparatus is disclosed in which heat is transferred between a grey water stream and a fresh water stream. The apparatus comprises: a grey water flow path leading from a source inlet to a drain outlet; a plurality of heat exchangers arranged in said grey water flow path; a separator arranged upstream of said heat exchangers, arranged to separate grey water from the source inlet into a plurality of parallel sub-paths, each sub-path being lead to one of the heat exchangers; and a collector arranged downstream of said heat exchangers, arranged to reassemble the grey water from the sub-paths into a single flow path. Each heat exchanger comprises a grey water tube extending from the separator to the collector, and an outer tube surrounding at least a part of the grey water tube, the outer tube defining an annular space around the grey water tube. A fresh water flow path formed within the annular spaces around the grey water tubes in the heat exchangers has a flow direction being opposite to the flow direction of the grey water.

A waste water diverter may have a housing, which encloses a cavity, a waste water inlet arranged at an upper end of the housing and opening into the cavity. The diverter may also have a grey water outlet and a black water outlet, which are connected to the cavity, and arranged at a lower end of the housing. A guide plate may be arranged in the cavity to be pivotable about an axis of rotation between a first position and a second position via a drive such that waste water flowing in through the waste water inlet is guided by the guide plate in the first position into the grey water outlet and the black water outlet is blocked, and in the second position the grey water outlet is blocked by the guide plate and the waste water is guided into the black water outlet.

A plumbing or ablutionary system is provided, in which a water supply stream flow path from a water supply inlet to a water supply outlet, such that a water supply stream flowing in a water supply pipe is in an antiparallel counterflow heat exchanging relationship with a waste water stream flowing along a length of a serpentine portion of a waste water conduit. When the waste water stream has a higher temperature than the water supply stream heat is exchanged from the waste water stream to the water supply stream, thereby increasing the temperature of the water supply stream.

A heat recovery unit for recovering heat from gray water while protecting the fresh water source from contamination is disclosed. The unit comprises an inner tube and an outer tube being larger than the inner tube for enclosing the inner tube creating a conduit between the inner and outer tubes. As such, the unit indirectly transfers the heat from a hot gray water source to a cold fresh water source that supplies fresh water to baths, showers or a water heater. The heat recovery unit further comprises an intermediate annular space between the inner wall of the outer tube and the outer wall of the inner tube. The intermediate annular space contains a third liquid, preferably a food grade liquid, such as distilled water, for providing a protective barrier between the inner and outer tubes.