Geothermal Loop Leak Verification

The purpose of this Service Advisory is to identify and verify leaks in geothermal closed loop systems. The procedures in this Service Advisory are only guidelines to help assist in troubleshooting for loop leaks. Any questions regarding loop leak testing should be directed to our technical services team at 1-800-665-3336.


Insert the pressure gauge into the "water in" P/T port ( pressure / temperature ) and the repressurizing device (see drawing at end of this article ) into the "water out" P/T port. Begin pressurizing the loop by adding water. Continue to watch the pressure gauge; if it takes a while for the gauge to move, this is a good indication that air is in the loop, but does not necessarily mean there's a leak (remember, air can be compressed, not water).

Once pressure is back on the system, another sign that there is air in the loop is fluctuation in the loop pressure which is indicated by the bouncing gauge needle. The geothermal ground loop needs to be reflushed if air is present. If the pump is making noise, this is another sign of low pressure or air in the system. The pump should quiet down after repressurizing,

*NOTE: Low loop pressure may be the result of pipe expansion do not immediately assume you have a leak in the loop!


There are various methods for determining if there is a leak in the loop piping system. Do not pressure test the inside piping through the flow center. An outside leak could not be distinguished from an inside leak since the flow center joins both inside and outside systems.

To isolate the inside piping from the outside portion (DO NOT remove white flushing plugs): Turn the 3-way valves on the flow center so that the outside loop is closed off. This will make it possible to pressure test the flow center and the piping to the unit(s).


100 psi is more than enough pressure when pressure testing a closed loop . WaterFurnace recommends a 100 psi gauge, 2-1/2" or 3" in diameter in 1 psi increments. Due to expansion of polyethylene pipe, the pressure on the system will drop about 10% on the initial pressurization and about 5% on the second.


To test for outside leaks, cut the inside piping off at the supply and return lines and pressure test at the wall penetration before digging up the outside portion. Once it has been determined that the leak is outside, the manifold should be excavated to expose all the loop lines. After exposing the manifold, put pressure back on the loop and check the manifold for leaks.

If there are no leaks in the manifold, cut the 3/4" lines off at the manifold one circuit at a time and pressure test each individual circuit. If a leak is found in a circuit, corrective action will depend upon what type of loop was installed (see below).

  • HORIZONTAL LOOPS : Go to the end of the trench and pressure test the top line back to the manifold. Do the same with the bottom line to determine which line the leak is in. From there, it's a process of elimination. For example, dig up the middle of the trench, and pressure test each direction until the leak is found. If there are fittings in the ground, it would be a good idea to check at those points first. Additionally, most of the leaks that have been found are close to the beginning of the roll of pipe. The pipe was usually damaged from shipping (which means it is on the outside of the coil, such as a fork lift puncture). Usually, the most cost-effective approach is to add a new circuit to the loop.
  • VERTICAL LOOPS : Use the same process as the horizontal loop as far as the manifold is concerned. If the leak is in a circuit, abandon the circuit and add a new one.

  • POND LOOPS : Use air to force out the fluid in the loop (this can be pumped into drums and reused most of the time). This will allow the loop to float to the surface, making leak repair possible.

Should you have any questions on this ground loops testing procedure do not hesitate to contact our team at 1-800-665-3336. We stock and sell all service tools required to expedite ground loop testing and commissioning and are happy to help with any questions you may have.

Loop Re-Pressurizing Device


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