First check the hose connections to the filter. Hopefully you have the double shutoff valves so you can disconnect the filter without loosing water. The intake tube is connected to the bottom connection on the cannister. If it's leaking at the top take the cannister apart and check and lubricate the 0-ring. I find a easy way to prime is to connect the top filter outlet to a bucket on the floor, suck the tube and water should start flowing. I power on the filter and let it run into the bucket until all air is purger, shut down and reconnect to outlet hose. User manuals are at eheim.com