Pool and Spa Heater Gas Lines in Spartanburg, SC

Natural gas carries roughly 1,000 BTU per cubic foot. A 400,000 BTU heater running at full fire therefore burns about 400 cubic feet of gas an hour. For comparison, a typical tank water heater burns around 40, and a furnace somewhere between 60 and 100. The pool heater is the elephant on the line.

Pipe sizing in the fuel gas code works from two numbers: the total flow the pipe has to carry and its developed length, meaning the full distance along the pipe, not as the crow flies. Double the length and the pipe has to get larger to deliver the same flow at the same pressure drop. A run that would be fine in three-quarter-inch for a grill can need one and a quarter inch or more for a big heater at the end of the yard.

The heater has a minimum inlet pressure printed in its installation manual. When it fires, our job is to make sure the pressure at its gas valve stays above that number, with everything else in the house running too. That is the test that matters, and we take the reading with the heater lit.

The utility sizes the meter and its regulator for the load it expected when the house was built. A house with a furnace, water heater and range might have a meter that was never meant to pass an extra 300 or 400 cubic feet an hour. Add a pool heater and the meter itself can become the bottleneck, no matter how big the pipe after it is.

We add up the connected load before any digging starts. If the total looks beyond what the meter is likely to deliver, the utility has to review it and may need to swap the meter or regulator. That is their equipment and their schedule, so we raise it at the start of the project, not the week the pool is filled.

In some cases the better answer is an elevated-pressure line to the pad, where the utility delivers gas at 2 psi and a regulator at the heater drops it to appliance pressure. Higher pressure moves more gas through smaller pipe, which can make a long run practical. It needs the utility's agreement, and the regulator has to be one rated for outdoor use and installed where it can be reached.

Most pool heater lines leave the house above ground in steel, drop into the yard and run underground in polyethylene to the pad, then rise back out of the ground in steel at the heater. Plastic gas pipe is never run above ground. It gets a tracer wire alongside so it can be found with a locator later, and the transition fittings at each end are listed for the purpose.

Trenching in a finished backyard takes planning. Irrigation lines, landscape lighting, pool plumbing and the pool's bonding grid are all in the way, and none of those are marked by SC811 because they belong to you. We locate what we can, ask what you know, and route around the pool shell and deck.

At the heater the line ends in an accessible shutoff valve and a sediment trap before the appliance connector, the same as any gas appliance. The heater manufacturer also sets clearances from windows, doors, air intakes and overhangs, so the location the pool builder picked sometimes has to move a few feet.

On a new pool, the gas line is one trade among several, and the timing matters. The best time to trench is before the deck is poured and the yard is sodded. We coordinate with the pool builder on where the pad goes and when the trench can be open, and the underground pipe gets its pressure test and inspection before the trench is backfilled.

On a replacement, the question is whether the existing line was ever sized properly. Many older pools had a smaller heater, and many lines were run by whoever was on site at the time. Swapping a 250,000 BTU heater for a 400,000 BTU model on the same pipe is the most common way to end up with a new heater that keeps faulting. We check the existing pipe size and length against the new heater before you order it.