I have a five year old Carrier geo, horizontal closed loop system. I've always had an annual service plan with a local company. For first four years I had used the installing company (Carrier geo certified) and last year I switched to a different company (geo experience but not Carrier dealer) to save $. I'm looking to go back with a certified Carrier shop for my service and am wondering how often these really need to be maintained? Is annual enough or is it better twice/year? I prefer to have the loop pressure necked more than once/yr (reason below * if you care). Can a homeowner get a pressure gauge and check themselves? What is ideal loop pressure? Is a pressure as low as 5 psi ok if system is working ok otherwise (proper temps, etc)? Thanks! Recently the tech was here and found loop pressure was extremely low. He tried to add fluid but it started leaking badly at loop IN fitting. He tried to tighten it but (I believe) he made the problem worse by (further?) marring the gasket. The tech left things as is saying the fitting needed to be changed ($300 + labor) saying they had to buy the entire fitting, not just the gaskets. I contacted thenoriginal service company and they had the gaskets in stock and were able to fix quickly and much less $. Fwiw the tech who found the pressure low said it was 5 psi. When I asked the tech who fixed the leak (who's been here many times) what pressure it should be he was evasive with his answer, basically saying he would've left it be @ 5 psi saying they generally leave it be if there's pressure and everything is working ok otherwise.