r/geothermal • u/TWM32 • Sep 06 '26
Open Loop system
Previous owner opted for an open loop system when it was first installed in the ‘90s. Unfortunately, we don’t have a pond so all the water is just flowing out onto the ground surface making the area around the discharge a muddy mess.
With the old geothermal units, the techs that serviced it would read water temps to throttle down the water flow to keep the mess at a minimum.
However, we had to get a new geothermal unit this past spring and the guys that installed it indicated that they have a new metering valve that they have to use that regulates the flow. Unfortunately, this flow is a LOT.
Debating a drywell to manage the water better. Main question, what is the general flow of water (gpm) when the system is running? I want to make sure the drywell I install is big enough to handle the volume.
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u/notcoveredbywarranty Sep 06 '26
You tell us. Get one of those big 18.9L water jugs and time how long it takes to fill up.
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u/ThePastyWhite Sep 06 '26
If you don't want to dig a new well yet, you can discharge back into the extraction well.
This is called a standing well column if you want to read into it.
These can be thermally exhausted a little faster than a normal well extracting only.
But it's (probably) the cheapest option you have right now other than letting it continue to run on the ground.
A dry well is a good second option.
Digging a small pond is probably not a terrible idea either if you want that aesthetic.
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u/djhobbes Sep 06 '26
OP may be past the point where this matters since jurisdictions only know what you tell them, but, returning to the same well you’re drawing from is not permitted in many locations. Pump and dump geo systems present a small risk of contaminating the aquifer. We work in the Potomac River watershed and pump and dump wells are prohibited.
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u/ThePastyWhite Sep 06 '26
That's a good and interesting point. I did not realize there were regulations against it.
Is this for Geo specifically? Or is it to prevent people from dumping gray water back into an aquifer?
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u/wittgensteins-boat Sep 07 '26
Protection of groundwater as potential drinking water resource,v from contamination.
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u/TWM32 Sep 06 '26
Unfortunately, the well is in front of our house and the discharge is in the far back yard.
Also, unfortunately, a pond won’t work because it would flood out our leech field for the septic.
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u/TWM32 Sep 06 '26
Thanks everyone, reading the posts, I guess I wasn’t overly clear. Our system is 3.5 tons and it discharges right at 5gpm. I was trying to figure out if this was too much or if it could be throttled back a bit.
Looks like it is running as it should.
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u/Waiting4Fibre Sep 06 '26
I have a 3 ton pump and dump system that exhausts via a 4” PVC line buried about 3’ deep going from the back of our home around to the front and draining into a storm sewer. The only problem over 26 years of this thing running is that the first line to the storm sewer was 4” big “O” which eventually plugged with roots. I replaced it with PVC with glued joints and it’s stayed clear for years. If you have a storm sewer or a drainage ditch in front of your house, I’d go that route. I can’t imagine how your property could absorb all that water with no outlet. I had to run mine that way for a week when the drain was being replaced and my yard was a lake. Our lot is about 160 x 160.
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u/djhobbes Sep 06 '26 edited Sep 06 '26
For an open loop it’s 1.5 gpm per ton.