I had a pressure cleaner for over a year. Last week was the first time I assemble it and try to use it. The power is on and water hose fitted to the equipment and the unit was producing some sound and seemed that it was ready to be used. When I pressed the trigger no water came out! I tried it a few times and waited for the unit to run for 20 seconds before pressing the trigger again. Still no water! Just wonder what could go wrong! Can someone help?