What's This?????

Water heater in new construction did not have a thermal expansion tank but did have some sort of valve (?) (just above knob and before the pvc piping). Any idea what this is and does it take the place of a thermal expansion tank? Thanks!

Water Heater Today.jpg

Yes and yes depending on jurisdiction.

Series: **53 **
Description: Pressure Relief Valves
Size Range: 1/2, 3/4 in. (15 to 20mm)

Series 53 Pressure Relief Valves are used in residential applications to protect against excessive pressure on domestic storage tanks and tankless water heaters. It consists of a bronze body construction with NPT threaded male inlet and NPT threaded female (drain) outlet connections, and stainless steel spring. ANSI Z21.22 approved, ASME rated, and design certified and listed by CSA. Pressure Range: 75 to 175psi (5.2 to 12.1 bar), Standard Pressure Setting: 75psi (516.7 kPa), Optional Settings: 100, 125, and 150psi (6.9, 8.6, and 10.3 bar); Also available at 50psi (3.45 bar) setting.

Awsome! Thanks Michael