UV lamps used for sterilisation purposes should be replaced every 6 months (approx. 4000 hrs) to ensure the continuous high output that is required for these applications. Lamps used for clarification of ponds can be replaced once a year (approx. 8000 hrs) without detriment to the effectiveness of the unit under normal circumstances. Whilst replacing the UV lamp, the quartz sleeve should be carefully cleaned with a light acid cleaner and washed with water to remove any deposits and dirt that may have built up. The quartz sleeve should be completely dry before replacing it in the unit. The quartz O-rings should be replaced to ensure an effective seal between the quartz sleeve and the plastic body.