A preassembled modular vacuum plumbing assembly for attaching a plumbing fixture to a water supply system and to a vacuum-assist waste removal system includes a frame having two upright members and at least one connecting member between the two upright members. At least one water supply conduit is attached to the frame, each water supply conduit having a first end configured for attachment to the water supply system and a second end configured for attachment to the plumbing fixture for providing water from the water supply system to the plumbing fixture. An accumulator is associated with the plumbing fixture for receiving and holding water provided by the at least one water supply conduit to the plumbing fixture. A wastewater outlet conduit is attached to the frame, the wastewater outlet conduit having a first end attached to the accumulator and a second end configured for attachment to the vacuum-assist waste removal system for directing water from the accumulator to the vacuum-assist waste removal system.