Could my skimmer be clogged?

Hey all..I'm new to 3 reef and love all the info I've found here. I've had my tank running for about 3 years and have never had a skimmer. I did get a used one when I bought another tank. My question is I have a Berlin Classic with a Rio 2500. I've tried to run it on a trash can to see how it runs. The thing is the out flow is very low and no foam. It may be cause I'm using tap water to test the skimmer. I would think there would be more flow. It's about a half gallon per minute. Let me know I'll be trying to place it on the sump soon. Thanks

 

Protein skimmers work better in salt water with a higher PH. Give us a post once you add it in. We'll go from there.