Before Anybody Digs: Where Geothermal Loop Leaks Actually Are
Short answer: In my records, most geothermal loop leaks are not in the buried pipe. They are at the clamped, gasketed joints inside: pump flanges, hoses, fittings, valves and purge ports. In 700+ geothermal jobs at Hartzell’s Heat & Air I have not replaced a loop field. A pressure test with the loop isolated settles it before anybody digs.
4.8 stars, 300+ Google reviews
Why is the buried pipe the last thing I suspect?
Because of how it is joined. ClimateMaster limits in-ground loop piping to heat-fused polyethylene and warns against threaded plastic-to-metal fittings because of “their potential to leak.” A fused joint has no gasket, no o-ring and no threads. The pipe ends are melted into one piece, and the Plastics Pipe Institute puts the design life of that pipe at typically more than 50 years. What hangs on the wall in the mechanical room is the opposite: clamped and threaded joints with rubber holding the fluid back, living with heat, cold and vibration. I started in this trade at 16, working alongside my dad, and 47 years later the buried pipe is still the last place I look.
“We don’t replace the loops. They last.”Dave Hartzell, Hartzell’s Heat & Air, Kingfisher
My records back that up. In the 700+ geothermal jobs Hartzell’s Heat & Air has on record since 2017, there is not one loop field replacement, and buried-loop leaks are a handful of one-off incidents. When something in a loop system gets replaced, it is a loop pump, a pump o-ring or a flow center. Loop pumps and flow centers alone came up 45+ times.
How does Hartzell’s find a geothermal loop leak without digging?
With a pressure test, done in the order ClimateMaster lays out in its loop leak bulletin. First the inside piping is tested on its own, with the flow center valves turned so the outside loop is closed off, because a test through the flow center cannot tell an inside leak from an outside one. Then the outside piping is disconnected near the flow center, capped and pressure tested by itself, before anybody digs up the yard. ClimateMaster says 100 psi is more than enough for that test, and that polyethylene stretches a little under pressure, so the gauge drops about 10% on the first pressurization and about 5% on the second without any leak at all. If the outside loop holds, the loss is inside, on the wall, where I can reach it.
That matters because a pressure test costs a service visit, and a loop field is a big share of what a geothermal system cost to put in. Once a yard is opened up, nobody undoes it if the answer was a worn o-ring.
Where are geothermal loop leaks inside the house?
When the loop holds pressure with the ground side isolated, I work the equipment side. These are the joints I check on Oklahoma geothermal jobs. The first two line up with what my records show actually gets replaced: loop pumps, pump o-rings and flow centers.
| Where I check | Why it leaks | What it looks like |
|---|---|---|
| Flow center and pump flanges | Gaskets between the pumps and the flow center live with motor vibration every hour the system runs. | Fluid or crusty residue on the underside of the flow center. |
| Hose kits and o-rings | Rubber hoses with swivel ends and o-rings age, and clamps relax. | A damp swivel end or a hose that weeps at the clamp. |
| Fittings and adapters | Every transition between materials is a joint doing work through the seasons. | Residue at a threaded or barbed transition. |
| Valves | Stem packing weeps even on a valve that works fine. | Wet or stained stem on an open valve. |
| Fill and purge ports | They get opened every time somebody charges the loop. | A port that was not closed all the way. |
What if the leak really is underground?
Then the next steps are still a process, not a backhoe across the whole yard. ClimateMaster’s bulletin has the manifold header area dug out first to expose the loop circuits, and if there is no leak there, each circuit is cut off the header one at a time and pressure tested. Once the bad circuit is found, the bulletin notes that the most cost-effective repair may be to abandon that circuit and lay a new one beside it. The usual underground cause I ask about first is a person: a fence post, a trencher on a new water line, a shed footing. That is damage, not a loop wearing out, which is why I ask what work has been done outside lately.
Should I put stop-leak in my geothermal loop?
I would not. ClimateMaster wants loop fluid filtered to 100 microns when a loop is flushed, because that fluid runs through the heat exchanger, the pumps and every port. A sealer circulates through all of that too, and it cannot tell the hole you want plugged from the passages that need to stay open. Find the joint and fix the joint.
What does a geothermal leak diagnostic cost in Oklahoma?
At Hartzell’s Heat & Air, the geothermal diagnostic is $348 flat. Weekday, night or weekend, it is the same $348, and it is the same for my maintenance plan members. It covers loop pressure, refrigerant charge, the desuperheater, controls and the heat exchanger, with a written report and a quote before I leave. If cost is the barrier on a repair, financing runs through Synchrony, Wells Fargo, Wisetack, Klarna or JB Financing. My shop is in Kingfisher, and for geothermal I travel across Oklahoma and into most of the states that border it, depending on the customer and the project. I am IGSHPA Accredited and a ClimateMaster GeoElite dealer, with 4.8 stars and 300+ Google reviews.
What you can do, and what to leave alone
- Note how often the loop has been topped off, and by whom.
- Look for wet spots or residue under the flow center and hoses, from a safe distance from wiring.
- Tell me about any digging, fencing or trenching in the yard since the loop went in.
Leave alone: valves, ports, hoses and loop piping, adding fluid, and stop-leak products.
Related: why your geothermal loop keeps losing pressure, HDPE loop fusion, pressure testing and flushing, why loop pressure changes with temperature.
Field video: Dave on a geothermal loop leak
Geothermal loop leak questions
My geothermal keeps losing pressure. Does that mean the loop in my yard is leaking?
Not by itself. Falling pressure tells you fluid is going somewhere, not where. The pipe in your yard is heat fused with no gasket or threads, while the joints inside are clamped and threaded. A pressure test with the outside loop isolated settles which side of the wall to work on.
How do you tell if a geothermal leak is underground without digging?
Test the inside piping and the outside loop separately. ClimateMaster’s loop leak bulletin has the outside loop disconnected near the flow center, capped and pressure tested by itself before anyone digs. If it holds, the leak is inside.
Somebody has been topping off my loop for years. What is really going on?
Fluid that keeps disappearing is going somewhere, and adding more treats the symptom. ClimateMaster calls at least one extra top-off after a complete heating and cooling season normal. Year after year means a joint nobody has found yet.
Can I add a stop-leak or sealer to my geothermal loop?
I would not. The loop fluid runs through the heat exchanger, the pumps and every port, and a sealer cannot tell the leak from the passages that need to stay open. Find and fix the joint instead.
Is old geothermal loop pipe more likely to leak?
The heat-fused pipe itself, no. The Plastics Pipe Institute puts its design life at typically more than 50 years, and I have loops on their third generation of equipment. What matters is how the loop was joined and whether anyone has dug near it.
How much does it cost to have a geothermal leak checked in Oklahoma?
My geothermal diagnostic is $348 flat, any hour, and the same for plan members. It covers loop pressure, refrigerant charge, the desuperheater, controls and the heat exchanger, with a written report and quote before I leave. Call 405-375-4822.
Sources
Test steps come from ClimateMaster’s loop leak bulletin and manual below. Job counts come from my service records since 2017, rounded down. The test results on your system decide where the leak is.