Watts LF100XL 175-210 3/4 3/4 IN Lead Free Self Closing T and P Relief Valve, 175 psi, 210 degree F, Test Lever, 4 IN Ext Thermostat

The LF100XL 175-210 has a 3/4 inch male NPT inlet, so it threads directly into a 3/4 inch female NPT T and P tapping on the tank. The shank below the threads is 1-1/8 inches long, and the copper thermostat probe extends 4 inches into the tank, so the tapping needs to be deep enough to clear that probe. The discharge side is 3/4 inch female NPT for the drain line.

Yes. The body is a lead free copper silicon alloy and the valve is flagged lead free, which is what a potable hot water heater application needs. The thermostat probe is copper.

Sizing comes off the discharge capacity, not the pipe size. The LF100XL 175-210 is rated for 200,000 BTU per hour on pressure discharge and 105,000 BTU per hour on temperature discharge. The temperature number is the one that governs on a water heater, so the heater's input rating has to be at or under 105,000 BTU per hour. A higher input heater needs a larger relief valve.

It has a test lever built in, so you can lift and flush the seat manually as part of routine maintenance without pulling the valve. It is a self closing design, and the 4 inch copper probe reads tank water temperature directly rather than the temperature at the fitting.

The 4 inch probe reaches past the tank wall and any lining or scale into the stored water, so it senses actual tank temperature. A short shank valve senses closer to the tapping and is used where a long probe would foul internal components or where the tapping is shallow. The LF100XL 175-210 3/4 is the extended version: 1-1/8 inch shank with a 4 inch copper probe. Check the depth available at your tapping before ordering the long probe.

It is flagged Buy American Act compliant, USA. For facilities buyers standardizing on domestic-sourced plumbing components across a portfolio, the ordering identifier is Watts part number 121344, model LF100XL 175-210 3/4.

The discharge port is 3/4 inch female NPT, so you pipe it with 3/4 inch full size drain line, no reducing, run downward to an approved termination. Nothing is threaded into that outlet from the factory and no drain tube ships with the valve, so plan on the pipe and fittings as a separate line item on the job.