Indoor plants in homes and commercial buildings such as malls, offices, airports, and hotels, can benefit from precision irrigation to maintain healthy growth and reduce water consumption. As ongoing manual adjustment of drip emitters may be impractical, we explore how the Toyota HSR mobile manipulator robot can autonomously adjust the screw-cap on each emitter. As the built-in sensors do not provide sufficient accuracy for gripper alignment, we designed a lightweight, modular Emitter Localization Device (ELD) with cameras and LEDs that can be non-invasively mounted on the gripper. This paper presents details on the design, algorithms, and experiments in bringing the gripper into alignment with a sequence of 9 emitters using a two-phase procedure: 1) aligning the robot base using the build-in hand camera, and 2) aligning the gripper axis with the emitter axis using the ELD. We report success rates and sensitivity analysis to tune computer vision parameters and joint motor gains. Experiments suggest that each emitter can be reliably adjusted in under 20 seconds.