Lodi sits on hard groundwater, and that one fact shapes how a pool heater should be sized, plumbed, and run here. Water drawn from wells around the Mokelumne carries a lot of calcium, and a heater is the one piece of equipment that deliberately raises water temperature at a metal surface. Every degree of rise across the heat exchanger pushes calcium closer to falling out of solution right there on the copper. On a pool that is even slightly out of balance, scale builds inside the tubes within a season or two. Flow drops, the unit starts tripping its high limit and short cycling, and a heater that should last fifteen or twenty years starts failing in five.

That is why heater & heat pump installation in Lodi begins with a water test and a look at the existing plaster, not with a product catalog. If the pool already shows a gray scale line at the tile or a rough patch on the steps, calcium is coming out of solution somewhere, and the next place it lands will be inside a brand new exchanger. We check calcium hardness, alkalinity, pH, and stabilizer before we quote equipment, and we talk through what the pool will need after the heater is running.

Nevergreen Pools serves Lodi in partnership with Vintage Pool Service, a longtime Central Valley company based off East Yosemite Avenue in Manteca. Between the two crews we set gas heaters and electric heat pumps across Lodi, Stockton, Manteca, and out toward Copperopolis, and we install them the same way every time: sized to the actual pool, vented to clearance, and plumbed so the next tech can service the thing without cutting pipe.

Should I put in a gas heater or a heat pump?

Gas is about speed. A gas heater makes its own heat by burning fuel, so it does not care whether the air outside is 100 degrees or 40. Fire it on a foggy January morning and it climbs at the same rate it would in July. That makes gas the right answer for a pool you use on short notice, for an attached spa, and for anyone who wants water warm enough to swim in through a Lodi winter. The cost of that speed is fuel. You pay for every BTU you burn, and running a large gas heater as a full time season extender adds up quickly.

A heat pump works the other way. It does not create heat, it moves heat out of the outside air into the water through a refrigerant circuit, so it delivers roughly four to six units of heat for every unit of electricity it draws. That ratio is the coefficient of performance, and it rises and falls with air temperature. Lodi summers in the high 90s and low 100s are close to ideal for a heat pump, and warm spring and fall afternoons still hold a good COP. The catch is the delta air at night. Once the temperature drops into the 50s the unit slows down hard, and a heat pump is slow to start with, moving a pool a degree or two an hour rather than heating on demand. Heat pumps reward an owner who holds a steady temperature under a cover, not one who heats from cold twice a month.

A fair number of Lodi pools end up with both, a heat pump carrying the water through spring and fall and a gas heater handling the spa on cool evenings. That combination is worth pricing before you commit to one or the other.

How is the heater sized?

Sizing starts with volume and the temperature rise you want. One BTU raises one pound of water one degree, and a gallon weighs about 8.3 pounds. A 20,000 gallon pool holds roughly 166,000 pounds, so lifting it ten degrees takes about 1.66 million BTUs of delivered heat. Divide that by the heater's output and you have a heat-up time before losses. Then you add the losses back, because a pool sheds heat off its surface all night, and an open Lodi pool under a clear October sky with a breeze coming off the river gives back a lot of what you paid for.

So we measure instead of guessing. What actually goes into the number:

• Real gallons, taken from length, width, and average depth, not the figure written on an old permit.
• Surface area and wind exposure, since surface loss dominates everything else.
• Shade. An older Lodi pool sitting under mature oaks and sycamores picks up far less free solar gain than an open pool on newer ground.
• Whether there will be a cover. A cover cuts overnight loss more than any equipment upgrade you can buy.
• Target temperature and how many months of swim season you actually want.

Undersizing is the common mistake. A heater that never quite catches up runs constantly, and constant run time on hard water is exactly what builds scale. Sizing up within reason is easier to live with, as long as the gas supply and the electrical service can feed it.