Can an Existing Geothermal Ground Loop Be Reused?

By Dave Hartzell, Master HVAC, IGSHPA Accredited, ClimateMaster GeoElite dealer, 47 years in the trade. Hartzell’s Heat & Air, Kingfisher, Oklahoma. Updated October 3, 2026.

Why can a geothermal loop outlast the heat pump?

Because the loop and the unit wear out on different clocks. The Plastics Pipe Institute puts the design life of heat-fused HDPE ground loop pipe at typically more than 50 years, and Pacific Northwest National Laboratory notes closed loops “can have 50-year warranties.” The heat pump above it has a compressor, a blower, a board and a pump, and those are the parts that wear. That is why, in my book, a geothermal “replacement” means the unit, not the loop.

“We don’t replace the loops. They last.”Dave Hartzell, Hartzell’s Heat & Air, Kingfisher

What has to be checked before an existing loop is reused?

A long design life does not mean every loop is good. I test it before I put a new unit on it. Here is what I look at, and the ClimateMaster or industry standard behind each one:

Pressure comes first. ClimateMaster’s loop leak bulletin has the inside piping and the outside loop tested separately, isolated at the flow center, so a leak in the house is never blamed on the ground. Then flow and purging: ClimateMaster calls for flushing at 2 feet per second with a flush cart and 100-micron filtration, and says a loop is clean of air only when a dead-head test drops the fluid 3/8 inch or less.

Does a bigger new unit need a bigger loop?

It can. A loop is sized for a load, and if the house grew, or the new heat pump is larger than the old one, the old loop may not carry it. I do not size the new unit off the old unit’s tonnage. I run a heat load calculation on the house, ASHRAE and ACCA Manual J methods, then check whether the existing loop can deliver the flow and temperatures that unit needs. When it cannot, the fix can be adding loop to what is already there.

What does reusing a loop mean for cost in Oklahoma?

It changes the job. The loop is a big share of a new geothermal install, and a sound loop does not have to be bought twice. If the unit itself is worth saving, a geothermal rebuild at Hartzell’s starts at $3,500 installed, with up to a 5-year warranty when the loop verifies good. If the unit is done, a replacement on the existing loop is priced in writing after I see it, and the estimate on a new system is free. A failed unit gets a $348 flat geothermal diagnostic first, any hour, and the same $348 for plan members. That covers loop pressure, refrigerant charge, the desuperheater, controls and the heat exchanger, with a written report and a quote before I leave.

Can I reuse a loop someone else installed?

Often. Most of the geothermal systems I service on homes, farms and acreages across Oklahoma were put in by someone else. What matters is the testing above, plus any paperwork you can find. Records make the call faster, and missing records just mean I test more. I am IGSHPA Accredited and a ClimateMaster GeoElite dealer, with 4.8 stars and 300+ Google reviews, and I work geothermal across Oklahoma out of Kingfisher.