Pool Heaters & Gas Pressure

by John Galcius, October 15, 2009
pressure gaugeAll pool heaters have problems and need service and troubleshooting at some point. Usually, these problems have nothing to do with the heater at all. The number one cause of heater failure is water flow or pressure. If a pool heater is not getting enough water, the pressure switch will shut it down, to prevent overheating. Another cause of heater failure is low gas pressure. Low gas pressure, Natural or Propane, can cause sooting, improper flames, “whistling” of the heater and believe it or not, overheating. According to Hayward, one of the world’s leading pool heater manufacturers, low gas pressure is the leading cause of pool heater failure.

There can be several causes of low gas pressure. Below is a list of the most common:
  • ·         The gas meter is too small
  • ·         The LPG or propane tank is too small or tank level is low.
  • ·         One or more gas valve leading to the heater 
  • ·         Gas feed line is too small. (refer to owners manual)
  • ·         Plug or clog in the gas line.
  • ·         Air not bled from the gas line. Usually on new installations.
Determining the gas pressure is easy if you have the correct tools. Gas pressure is measured in “Inches Water Column”.  Usually measured by a manometer, available at any plumbing supply store. The manometer is connected to the gas line or gas valve in the heater. The typical heater requires 4” to 10” water column to operate correctly. 27.71 inches of water column equals 1 PSI, so you can see, the gas pressure required to operate a pool heater is quite low, usually 1-2 psi. Even the difference in a few inches water column can affect the operation of the heater.
Not only will low gas pressure damage your heater, it will void the warranty immediately. That is a costly oversight. Newer construction and installations in this area (Washington D.C. Metropolitan Area) have what is called “high pressure”. High pressure gas usually runs about 2 PSI, so there is usually enough gas pressure to operate the heater. Older installations, and replacement heaters are a different story. Half of the installations we run across, do not have adequate gas pressure to meet manufacturers specifications. That meant a voided warranty. Not good for the pool owners, who have no idea.
If there are other gas appliances on the same line, this can reduce the gas pressure to the heater, causing performance issues. Long runs of pipe, from the meter to the heater, require a larger pipe size diameter to deliver the proper gas pressure.
So, if you are installing or replacing a pool heater, be sure to read the installation manual, and check the gas pressure. It will be well worth it.