Estate for years. An estate for years is one which is to continue for a definite period fixed in advance by. agreement between landlord and tenant. The name is somewhat misleading because the period may be for less. than a year, measured in specific days, weeks, or months. Estate from period to period. An estate from period to period (or periodic tenancy) is one which continues for. periods of time (typically year-to-year, month-to-month, or week-to-week) as designated by landlord and tenant. in their agreement. The most common periodic tenancy is the month-to-month tenancy.
You will still require 8.34 BTU to raise the temperature of a gallon of water one degree F. 1  I say approximately because the weight of water varies slightly with its temperature. 2  Water is at its densest at 4 degrees Celsius (39 degrees F). 3  A gallon of water at temperatures above and below that value will weigh less.
We would recommend at least an 85,000 BTU heat pump for a 20,000 gallon pool. If you would like to extend your swimming season into the late Fall or early Spring or you live in a colder area we would recommend a larger unit like the AquaPro 112,000 BTU or AquaPro 137,000 BTU models.