Most routine maintenance for geothermal heating & cooling systems can be performed by homeowners if they choose. If they’d rather not, just give us a call to schedule an appointment. Refer to Homeowner Maintenance section of your heat pump Owner’s Manual. Here are some items that require routine attention to keep your system running at peak performance:

Air Filter

If some or all of your system includes forced-air heating or cooling, then you should periodically check the air filters for each air handler.

If your heat pump is combined in one encasement with an air handler which is connected to ductwork – a common furnace replacement, then you’ll likely have pleated air filter(s) which should be replaced periodically. Frequency will depend on factors such as system usage and airborne particulates in your house. Every six months is a reasonable starting frequency; adjust based on experience. Air filters can be purchased directly from:


MERV 11 pleated filters are recommended for all Geostar packaged – heat pump/blower combination – units. 2-inch width for Sycamore, Aston, and Cypress models; 1-inch for Magnolia Plus.

If you have a washable air filter, check every 3 months or so and clean with mild detergent and water as appropriate… after removing it from the unit.



If you have a hydronic (or water-to-water) heat pump which provides heated or chilled water to one or more remotely-located air handlers, check the air filters on each air handler and clean or replace as appropriate.

Multiaqua hi-wall air handlers are ductless, but they still have air filters. Check your owner’s manual for instructions to remove and clean the air filter.

Hydronic ducted air handlers also have air filters. Depending on the manufacturer and model, they may be washable or disposable. Check these at least every six months, as well.

Flow Center Water Level

If your ground (or water) heat exchanger is a closed loop, you have a flow center which is the interface between your heat pump and loop, and manages the loop flow rate through the heat pump. If the flow center is non-pressurized (NP), it is comprised of a tank of water piped to the loop and heat pump(s), and has one or more circulating pumps mounted on the outside of its frame. It is critical to the function of the system that the water level never be allowed to drop below the intake of any of the circulating pumps. If that happens, air will be injected into the loop which could restrict the flow of loop water through the heat pump, negatively impacting the system efficiency or, in worse case, cause the system to shut down until the situation is resolved. Even if the water level is raised back above the circulating pump intake(s), it may take weeks or even months for the air in the loop to be completely ejected back into the flow center cavity, which will require frequent checking until all the air has been ejected and the water level in the flow center stabilizes. If the low water level is allowed to persist, the circulating pump(s) could overheat, resulting in permanent damage.

To that end, modest amounts of water will need to be added periodically to account for evaporation and dissolved air coming out of solution. This is easily accomplished by the homeowner, if (s)he follows the directions outlined below. In the first several weeks of operation following filling or re-filling of the loop, significant amounts of dissolved air will come out of solution and collect in the flow center cavity. During this time, the flow center water level should be checked at least weekly and topped off. This frequency can be reduced once the water level stabilizes. Even after the water level is stable, check the water level and top off with clean water once a year as modest amounts of water will be lost from the loop due to evaporation. (Hard water, softened water, or water with dissolved iron should not be used.)

The easiest and safest time to check the water level is while the heat pump (and thus the flow center) is running. This ensures that water in the flow center is being continuously pumped back into the loop and will not accumulate in the flow center and spill out the opening at top (due to runback from piping that may be above the elevation of the flow center). To ensure that the heat pump and flow center continue to run while you’re checking the water level and adding water (if necessary), temporarily increase the thermostat setting of your largest zone (if your house is zoned) at least 5 degrees above current room temperature in heating mode (or decrease the setting if in cooling mode). Note: if you have a hydronic or water-to-water system, you may have to wait several minutes for the buffer tank temperature to drop low enough to trigger the heat pump to activate. Once you are assured that the heat pump is running, remove the 5- to 6-inch diameter screwcap on the top of the flow center to check the water level. Add clean water to raise the level to within 4-6 inches from the top. Do not fill to the top, especially in heating season, as the water in the loop is relatively cold then and come cooling season the water will warm and expand which could result in water overflowing the flow center (even if the cap is securely attached).

Load Side Hydronic Pressure

If you have a hydronic – water-to-water – heat pump, check the pressure gauge on the load side – the piping that distributes heated (or chilled) water to air handlers and/or other heat emitters (e.g. baseboard). Appropriate hydronic pressure will be dependent on the elevation difference between the highest point in the system and the pressure gauge. For every 10 feet of elevation, add 4.3 psi of gauge pressure… then add 5 psi . For example, if you have an air handler in the attic which is 25 feet above the gauge, the hydronic pressure at the gauge should be no less than ~18 psi; otherwise, call for service. If gauge pressure is above 25 psi, you’re at risk for water leakage through the pressure relief valve(s), typically on the buffer tank.

Condensate Drip Pan, Drain Line, and Pump

If you have air conditioning, check your condensate disposal system at least annually. Beneath the air coil in your air handler is a pan to collect condensed water vapor during the air conditioning process. After disconnecting power to the air handler (which may mean to the heat pump if you have a packaged water-to-air unit), check and clean the pan, drain, drain pipe, and condensate pump (if you have one). These can be a haven for mold and/or algae growth. A mild solution of bleach will generally remove both. In between annual cleanings, if you notice water puddles during air conditioning season, check if the condensate removal system is clogged or if the pump is working – it’s activated by a float in the reservoir.

Air Coil

This is a network of metal (typically aluminum) fins and tubes that delivers heating or cooling to the blower of an air handler. Generally, it should not need maintenance or cleaning unless the air handler has run for a significant period of time with a very dirty air filter or none at all. If there is dirt or debris build-up on the coil, call for service as you don’t want to risk damage to coil during cleaning.

In Geostar water-to-air heat pumps, the air coil is located behind the air filter. Hydronic air handlers often use an A-shaped coil mounted below the blower (in a vertical unit).




If you have a flow-through drip-style humidifier on the duct system, check the specially coated metal or plastic screen for hard water build up annually. Clean or replace as necessary.




If you’re ever in doubt, give us a call. We service what we install!

Also, read about dehumidification and inadvertent use of auxiliary electric resistance heat.