Abstract: A flowmeter comprising a one-piece flowmeter body molded of suitable transparent plastic resin. The body has an inlet and outlet port molded therein with a tapered metering tube extending therebetween. A float ball is disposed within the metering tube and is movable therealong in response to changes in the flow rate of fluid flowing through the flowmeter. A valve is sealably installed in the inlet port and an outlet fitting is sealably installed in the outlet port. A retaining plate is received in grooves molded in the back of the flowmeter body with the retaining plate being slidable between an unlocked position in which the fitting and the valve may be installed in or removed from their respective ports in a locked position in which the retainer plate positively and sealably holds the valve and fitting in their respective ports.