If you are tired of messing around with the plastic UVs the ZapTek units deserve your consideration. This will be the last UV you'll have to buy. These are 3" units that come with 2" bushings so you can use them with 2" or 3" pipe. Very hard to find 3" UVs. 7 sizes to fit every project. The 13,000 HR lamps set the industry standard for long term dependability. It's easy to tell if you have electricty to the unit because it has its own lighted indicator as does each lamp on the dual lamp models and single indicators on the single lamp unit. With flows up to 13,200 GPH they handle whatever pond you might have.