An open loop geothermal system can provide your home with heating and cooling while requiring a smaller installation investment than a closed-loop type. However, there are several distinct differences in both function and upkeep. Here's what you need to consider if you're considering choosing an open loop system.
Water filtration may be needed
An open loop system has pipelines traveling to and from a body of water (either an aquifer or an aboveground body of water), supplying the HVAC unit with water for heat exchange purposes. Although the water doesn't exactly have to be drinking quality in order to work well for this purpose, it does need to be able to pass through pipes constantly for years and years without causing damage or buildup.
If your source is groundwater, then you probably won't need a treatment system unless your water is very hard. If you have very hard water, you may need to soften it before it enters the loop so that it won't cause limescale buildup on the inside of your system. If your water source is aboveground, it may have other contaminants such as plant life, algae, insects, fish, amphibians, and suspended dirt and silt particles.
If you do require a water filtration system, this adds costs to the setup and also ensures that you'll need to perform extra maintenance, especially if the system includes filters that will need to be changed or salt that will need to be replenished.
It needs a lot of water
You shouldn't just assume that because you have a private well or a pond, you can heat and cool your entire house with geothermal. You'll need to contact an expert and have all the calculations done, because heating and cooling the entire house requires heat exchange with a lot of water for hours at a time. Contact a company, like HELP Plumbing, Heating, Cooling and Electric, for more information on HVAC services.
Although the water is not technically used up by the process (it only changes temperature a little bit), this does mean that in areas with water shortage you may want to think twice before choosing open loop.
Local codes may limit disposal possibilities
There are a couple of things you can do with the water after it's gone through the system. You can use it for irrigation and landscape watering, but this may not answer for all of it. You can also replace it back in the ground or body of water it came from. However, putting it in surface water can be against local codes and can change the local ecosystem because it's a different temperature, so that's not always a good idea.
These considerations demonstrate that although an open loop system can be an ideal solution for some homeowners, there are still several considerations and some logistics to work through before you break ground.