I am in the process of purchasing a home heated by propane..someone has removed the pigtail from the tank to the regulator..the tank fitting appears to be a quick disconnect type unfamiliar to me..the supply tank is 20% full which means I would like to utilize this gas to test the house appliances.
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If the house is unoccupied it's likely "winterized", which may include disconnecting the fuel tank. You'll likely have to contact the home owner or fuel supply company, and make an appointment for them to meet you and reconnect the tank temporarily.
DO NOT RECONNECT THE TANK YOURSELF. If you do not own the property, it is not yours to muck around with as you please.
Tester is absolutely right. Do not mess with the gas supply! It is disconnected for a reason, either for winterization or because of a problem or leak. It is not yours to modify.
I am a certified home inspector and see homes with utilities disconnected all the time. My advise for you is to be sure to have as a condition of sale, that a complete inspection be conducted by a licensed/certified technician or inspector with all utilities connected and appliances commissioned for testing. This is known as a "contingency" on your purchase and sale agreement. It is always the responsibility of the owner/seller to handle utilities.
The heating plant should be inspected for proper operation and possible defects only by a licensed person.