Christian Missions in Persia. Christianity was introduced in Persia in the Parthian period, and several bishoprics were established there (Latourette, II, pp. 263ff.).
You will likely pay more for the exchange, even if your tank is completely empty. An empty 20 lb tank will hold about 4.7 gallons of propane. That is $18.47 at $3.93 per gallon, which is the low quantity price (I just paid $3.44 per gallon when filling several tanks). The exchange is about the same price. Keep in mind this comparison is as if the exchange gives you a FULL tank.
Residential storage tanks are typically 120, 250, 500 or 1,000 gallons, either above-ground or underground. 1  For safety, propane tanks should only be filled to about 80% of total capacity. 2  Propane is sold by private companies. Some homeowners own their propane tank, while others rent or lease it from the propane company.