Part number for just the knob?

The kit did not include separate part numbers. Just the bag of parts. Maybe a good hardware store can help you. Take the old one with you and match it up or drill a hole in an old one or a new one and using a thread cutting screw then install the screw to act as a pinching point on the existing stud. Just thoughts.

Is it difficult to replace this gas control cock valve and thermocouple in the fire pit?

I followed the picture and installed it according to the operating instructions. It's very easy to install.

Can I use this without the thermocouple? My propane fire pit does not use a thermocouple for its control valve.

No, I do not believe the unit will allow gas flow with the thermocouple uninstalled or unused (except when the control knob is held pushed in--the normal method to light a fire pit with a safety control.) You could experiment and see if gas flows with the thermocouple detached, when the gas is turned on, but not pushed in. (Pushing the control IN forces gas to flow, ignoring the thermocouple input while the unit lights and heats up enough to stay lit as detected by the thermocouple.) Bypassing the thermocouple is dangerous. Holing the gas knob in during all use is impractical. A better solution would be to drill a hole near the location of the sparker (igniter) and install the thermocouple there, allowing full, safe use of your firepit. This installation is included in the illustrations on the Amazon product description (seen from below). There is a real risk of continued release of gas if the unit does not stay lit and the gas continues to flow, possibly causing an explosion or fire or death by inhalation to nearby people or if used in an enclosed space. The purpose of the thermocouple is to prevent gas release unless it is burned inside the normal burner flame area. I suspect that this safety shut-off feature is required in most states and localities. It is also a very good idea.

Can this valve be used to replace valve on santos outdoor 56-inch rectangular propane fire table with tank holder by christopher knight home?

The valve did not work for me, but all i really needed was the thermocoupler, which ended up helping me fix my table. be sure you check the 65mbar/3/8" male valve connections, as this was what didn't work for me.

Material	Brass
Brand	WADEO
Item dimensions L x W x H	3.9 x 1.1 x 4.5 inches
Exterior Finish	Brass
Inlet Connection Size	0.38 Inches
Inlet Connection Type	Flange
Outlet Connection Type	Flange
Number of Ports	2
Outlet Connection Size	0.38 Inches
Manufacturer	WADEO
UPC	778299080125
Part Number	HK0229+HK0230+HK0231-IMUSA
Item Weight	6.4 ounces
Product Dimensions	3.9 x 1.1 x 4.5 inches
Item model number	WADEO[...]
Color	Brass
Shape	Round
Included Components	Control Valve,Thermocoupler,Platic Black Knob
Batteries Included?	No
Batteries Required?	No

WADEO Low Pressure LPG Propane Gas Fireplace Fire Pit Flame Failure Safety Control Valve Kit, Low Pressure Propane Fire Pit Replacement Part with 3/8" Flare Inlet & Outlet

Details

Description

Specifications

Common Questions