noted that because of the fluid tight engagement between the wall of piston member 54 and the wall of housing 42 any fluid flowing into bore 45 would be unable to by pass piston 54 and enter into any portion of the bore housing spring 66 therefore there would be no chance of spring 66 freezing through internal water contained within that housing during use of that valve fig4 9 illustrate an alternate embodiment of the present invention in those figures there is seen a relief 110 is shown for placement in a fluid line not shown to prevent cracking or rupturing of the line when fluid in the line freezes relief valve 110 is a tee having a first conduit 112 for placement in the line and through which fluid flows first conduit 112 can for example be a replacement section of pipe which is patched into an existing fluid line a second conduit 114 is in fluid communicating relationship with the interior of first conduit 112 the second conduit 114 having a cap 116 with a flat top 118 and a flat bottom 120 cap 116 is a hollow copper cylinder provided with internal threads 122 which mate with external threads 124 so that cap 116 sealingly engages open top 126 of second conduit 114 second conduit 114 extends into first conduit 112 so that flat bottom 120 is substantially coincident with the longitudinal axis of first conduit 112 bottom 120 is also provided with a centrally disposed aperture 128 through bottom 120 for establishing fluid communication between first and second conduits 112 114 an annular seat 130 circumscribes aperture 128 on the face of bottom 120 that faces the interior of second conduit 114 annular seat 130 is in the nature of a.