Abstract: A centering valve box adapter is provided for supporting a bonnet over a valve box to maintain vertical access to the valve box nut. A plurality of retainers can be affixed to the valve box using the bolts on the valve box. Each retainer has a lip and a keeper. Each keeper has a vertical hole. A plurality of brackets can also be provided. Each bracket can have an interface, an extension and a riser. The interface can be removably received within the hole of the keeper. The plurality of retainers and respective brackets form an assembly that defines a perimeter. A bonnet can be vertically supported on the respective extensions of the brackets. The bonnet is self centering and is laterally bound by the perimeter defined by the risers. The retainers and brackets can be made of stainless steel.