which preferably provides a seat feature for the piston 20 the piston 20 is preferably stepped and cylindrical and a smaller diameter portion 20 a enters the end 11 a of the body 11 and a larger diameter portion 20 b defining a circumferential surface 20 b u2032 see fig4 a downward facing piston seat 21 is defined by the step in the piston 20 a spring 22 resides in the nozzle 12 pushing the piston 20 against and into the end 11 a of the body 11 the spring 22 and piston 20 and seat feature of the body 11 create a valve between an interior 13 of the emitter 10 and ceiling 12 a of the nozzle 12 those skilled in the art will recognize that the seat feature of the body 11 may be the end 11 a of the body 11 or a separate seat formed proximal to the end 11 a of the body 11 and any seat formed on or attached to the body 11 for sealing cooperation with the piston 20 is intended to come within the scope of the present invention a cross sectional view of the subsurface emitter 10 in a closed position taken along line 3 3 of fig1 b.