Filling’s easy.  If you have any form of town water, use that.  To get the exact cost, call the water company, give them the amount of gallons, and they’ll tell you.  Generally, a 20,000 gallon pool holds about $90 worth of water.  If your town has separate sewer tax that’s based on your water usage, tell them what day you filled the pool, and ask for a waiver on the sewer tax – since you’re not flushing the water into the sewer.  This works in some towns.  If you don’t trust your well, it will cost about $400 to fill a 20,000 gallon pool using a good water company that will deliver drinking water.  Be careful, some water delivery people will back up to a local pond to fill up.  It’s cheaper (they’re getting the water for free), but it’ll cost you in time and chemicals to clear the water in your brand new pool.  For the same reason, don’t use a fire hydrant.  The stuff is full of rust!  Your builder may insist on trucking in water so that an entire crew doesn’t have to waste two days hanging around your yard watching the pool fill.  That labor cost could be higher than the water cost.

Electric costs to run your filter are difficult to predict – there’s such a wide range of pumps.  You’ll be running five to twenty-four hours a day, so figure maybe $25 to $75 per month.  A two-speed pump on a large filter can save you lots of money, as much as 40%.  For a big pool, a variable speed pump is the way to go; saving maybe 60% or more, plus preserving the environment.

Chemical costs can vary, as I discussed in the previous section.  With balancing, winterizing, and miscellaneous costs, I’d expect the owner of a 20,000 gallon pool will drop about $300 every summer.  Total for the summer; with chemicals, water, electricity and miscellaneous maintenance, most inground pools probably cost about $500 a summer to maintain.  Those numbers actually don’t change a lot if you use cheap chemicals or equipment, either.  Cheap chemicals make you buy liners more often.  Cheap equipment makes you replace it more often.  It all seems to work out in the long run.