Large green house cooling loop

I don't know where else to put this so I hope here is good and I hope you can help me out... we have a very large water cooling unit that is hooked (right now) to 14 loops of 3/4 plastic line 300 long the inlet pressure from the pump is about 30 psi, the return line is about 2 psi. the loop seems to be working with the low return pressure and is not cavitating (that we know of) as the cooling lines are almost the same temp going in and coming out. my fear is, my boss wants to add three more loops of the same size as this one (another 25,000 feet of pipe) this would be a total of four separate loops (like the one described) running off a header. My fear is there will not be enough pressure on the return side to feed the pump and cavitation is certain? and I am wondering if the current pump can even feed a system this large? the system now has 2 inch piping on the cooling unit feeding into 4 inch pipes that go to a 3 inch header with the four outlets running to a three inch header for each loop of 14 that are 3/4 plastic pipe all running at about 40 degrees f. could this work if we added another pump on the suction side of the pump? this whole thing is a closed loop system

thanks for any help in advance

 

I moved your thread here as this is a cooling issue.... not hot water.

You really need a systems engineer to figure this out.

I've read your post several times. Pretty hard to get an actual feel for the scope of the system. You are talking about a lot of buried pipe.

Inlet pressure 30psi and outlet pressure 2psi doesn't sound very encouraging.
If the inlet temps match the outlet temp...... how is this effective ?

 

I will be phoning the people who supplied the cooler. the system is laying on foam board insulation (as this is temporary system)and is covered by a small tent, the system is cooling this area about 12 degrees f and the lines are (very close) to the same temp on return. the cubic feet of area is quite small compared to the amount of pipe . the tents are 8 feet wide and only about 20 inches at the peak. when sunny the water is 40 degrees and at night it is 60. the pipes are only about 3.5 inches apart.