How to Replace a Honeywell Gas Valve

Switch off the electrical power and the main gas line.

Remove the gas input from the furnace with the wrench. Smell for any gas odor. If you detect gas either by smell or if you feel gas coming out of the pipe, re-attach the input to the valve, leave the electrical switched off and call a professional.

Unplug the wiring harness from the old valve. Place the pipe wrench on the flange or port where you disconnected the incoming gas. Rotate the valve counter-clockwise to remove it from the output pipe. Set the old valve aside.

Install flange adapters if the replacement valve's input and output ports do not match the size of the input and output pipes. Insert the O-ring in the flange groove; the O-ring faces the valve. Use the included hex screws to attach the flange to the valve. Repeat for the other port if necessary.

Note the "Outlet" marking on the top of the valve. Orient the valve so that the outlet port on the valve lines up with the outlet pipe for the furnace or water heater. Apply pipe compound to the threads of the outlet pipe on all but the last two threads so that the threads that first touch the valve have no pipe compound on them.

Turn the valve clockwise onto the pipe with the pipe wrench. Place the wrench on either the flange or the square valve casing where the flange would attach. Tighten the valve in place.

Connect the input pipe to the input port on the valve. Apply pipe compound in the same way to the threads of the input pipe. Twist the input pipe clockwise into the input on the valve until it is tight.

Mix the dish soap with water and brush it on to the connections. Turn on the gas and look for bubbles in the soap. If there are any bubbles, tighten the connections. Continue until there are no bubbles showing. Wipe off the pipes and the valve.

Plug in the wiring harness and switch on the power. Switch the valve into the "On" position. Light the pilot light per the instructions for your furnace or water heater.