Abstract: An electric water heater for heating a flow of pool or spa water includes an elongated metallic body of brass, bronze, aluminum or alloys thereof. A lengthwise elongated hollow in the body defines a water flow path having inlet and outlet openings directly communicating with the ends of the hollow. An electric resistance immersion heating element is positioned in the hollow between the inlet and outlet for heating a flow of water and is controlled by a heat sensing element, such as a thermostat, disposed in an opening in a thick body portion forming an elbow passage corner-turning the water flow path at one of the inlet and outlet openings. The thick body portion projects into the elbow passage and has a first face facing the opening and merging with a second face facing the elongated hollow at a convex locus extending widthwise across the elbow passage. The sensing element receiving opening extends widthwise of the convex locus.

Abstract: Thermostatic control of heating, as for a pool or spa, involves use of a heat source including a main heat generator and a mounting body, and includes:(a) a main high limit thermostat mounted in such relation to the body as to receive heat therefrom.(b) a thermal isolator plate operatively sandwiched between the body and thermostat, and(c) a heat conduction plate operatively sandwiched between the body and thermostat, there being an auxiliary heat source located to separately heat the heat conduction plate to cause heat flow to the thermostat,(d) the thermostat connected to interrupt operation of the main heat generator and operation of said auxiliary heat source in response to heating of the thermostat to a predetermined high temperature.

Abstract: In an underwater pool or spa light assembly for retaining an annular lens gasket and light housing in position, comprises:(a) a face ring having a central axis and annular re-entrant wall defining an annular flared portion to seat the gasket assembly, the ring also having retainer structure to retain said light housing which is engageable with the gasket to annularly compress same axially,(b) and circularly spaced tabs on the ring and projecting generally axially beyond the edge of the annularly flared portion to peripherally position the gasket, blocking radially outward extrusion thereof when compressed by the housing.

Abstract: Apparatus usable in controlling, both automatically and manually, a valve stopper movable between first and second positions to control fluid flow through the valve, comprises(a) a power source,(b) a drive coupling the power source to the stopper to move the stopper between such positions,(c) an input for transmitting movement between a manual actuator and the stopper to move the stopper between such positions, and(d) the drive including decoupling mechanism operable in response to the transmission of movement as defined in (c) above to interrupt the coupling of the power source to the stopper.

Abstract: A pool or spa water heater comprises:(a) a housing containing a combustion chamber,(b) gas burner means associated with the housing to produce hot products of combustion rising in said chamber,(c) a heat exchanger associated with said chamber in the path of said products of combustion to transfer heat to water flowing through said exchanger,(d) said exchanger including inner and outer metal tubes for transferring heat from the outer to the inner tubes and then to water flowing in the inner tube or tubes, said tubes having metal to metal contact,(e) whereby condensation of moisture from said products of combustion on exposed surfaces carried by the outer tubes is reduced.

Abstract: A light unit assembly adapted to illuminate liquid below a liquid surface (for example of a pool or spa) includes(a) a lamp unit including a metallic housing adapted to be cooled by heat transfer to the liquid, and lamp circuitry,(b) a thermostat coupled to the lamp circuitry to control electrical energization of the lamp, and(c) a heat conductive metallic strip associated with said housing and thermostat to become increasingly heated for changing the conductive state of the lamp in response to diminished cooling of the housing by said liquid.