I just recently had my 3rd FHP ES035 installed with a new loop field. This time I used a new contractor. To my surprise he used white PVC pipe between flowcenter and the the FHP unit (20 ft to HP). This was "glued" with the purple type compound. Originally when he had pressurized the system the first time he had to replace about 5ft of white PVC with the black HDPE GEOLink pipe that had been installed in front of the flow center. When I asked him why not use the HDPE all the way to the rubber hose connection (HP) he said it was not necessary: The operating pressure is only 15PSI and the white PVC is rated 200PSI... What is the correct static loop pressure? My other systems have always between 35PSI (lowest) to 60 PSI (highest) pressure. Is it ok to use the materials he used? BTW: My current static loop pressure is 12PSI (Jan 2011). The system was initially started in Nov 2010 and pressurized from/to the water line pressure of 40PSI. The only literature I found about this was @ waterfurnace and said: "...pressurize the loop to a static pressure of 40-50 PSI (summer) or 50-75 PSI (winter) ... "