Hi I'm new to this site and I am having trouble figuring out an issue we are having. I am at a 4 story condo building. The Air handlers are heat pump with a cooling tower. They have 2 pumps for the cooling water but they only run 1 at a time and switch them out every 6 weeks. In one stack (4 vertical units), the 1st, 2nd, and 3rd floor apartments have a working air conditioner with cool air coming from the vent. On the 4th floor the unit does not want to run, due to lack of cooling water. I removed both inlet and outlet hoses and checked the valves. The outlet side I can hear sucking air. The inlet side is dry and has no water coming out. I already tried to back-feed and flush the inlet side with water, and had no luck. I need help, any recommendations, next steps, ideas of the problems, or situations that you may have had that are similar to this? Thanks in advance for your help.