Troubleshooting Ride-Along: Can You Abandon Underground AC Lines and Run New Ones?
Location: Flagler Beach, Florida
Job: Full AC system replacement with existing refrigerant lines running underground.
Today’s adventure starts with something we see pretty regularly in Florida:
The refrigerant lines leave the air handler…
go down…
disappear into the house…
…and magically reappear outside beside the condenser.
Where were they in between?
Underground.
Welcome to Florida slab houses.
This isn’t automatically a problem. Plenty of underground refrigerant lines work for decades.
But we’re installing a brand-new air-conditioning system today.
And if we have a reasonable way to give that new system a brand-new, accessible line set?
We’re taking it.
So Are We Digging Up the House?
Absolutely not.
Nobody wants:
NEW AC INSTALLATION — NOW WITH FREE JACKHAMMER!
The existing refrigerant lines are already buried underneath the house.
We’re not removing them.
We’re abandoning them.
That means the old copper stays exactly where it is.
We’re simply not using it anymore.
Now we need another route between the indoor and outdoor equipment.
Time to look up.
We’re Going Through the Attic
The air handler location gave us a viable path overhead.
So instead of sending the new copper down into the slab, we routed the new refrigerant line set:
Up.
Through the attic.
Across the house.
Then back down to the outdoor unit.
Is crawling through a Flagler Beach attic our preferred recreational activity?
No.
Especially when the sun is out.
There are probably easier ways to lose five pounds.
But when we’re finished, the homeowner has new equipment connected by new copper that isn’t buried underneath the house.
We’ll take that trade.
Why Not Just Reuse the Underground Lines?
Sometimes we do reuse existing refrigerant lines.
There’s nothing automatically wrong with that.
If the existing copper is:
- properly sized for the new equipment
- compatible with the application
- clean
- undamaged
- leak-free
- and suitable under the manufacturer’s requirements
then reusing it can be perfectly reasonable.
We don’t replace copper simply because it’s old.
But underground piping comes with one enormous disadvantage:
We can’t get to it.
If something happens to that line later, we’re dealing with copper buried underneath a finished house.
That’s not where we want to go looking for our next refrigerant leak.
New System. New Accessible Route.
On this Flagler Beach installation, we had the opportunity to eliminate that problem.
The homeowner was already investing in a complete new HVAC system.
We had an attic route available.
So we installed a new refrigerant line set overhead and abandoned the underground copper.
Now the new system isn’t depending on a hidden line set from the previous installation.
And if we ever need to inspect or access the refrigerant piping in the future?
We know where it is.
That’s worth something.
But Doesn’t the Attic Get Really Hot?
Oh yes.
We can personally confirm that.
Repeatedly.
But refrigerant lines are routinely routed through attic spaces when properly installed, sized, supported and insulated as required.
The fact that the attic gets hot doesn’t automatically make it a bad route.
We account for the installation conditions.
And from a serviceability standpoint, we’d rather have properly installed refrigerant piping in an attic we can access than buried copper underneath a slab that we can’t.
Even if accessing it requires a bottle of water, a flashlight and several questionable life choices.
What Happens to the Old Underground Lines?
Nothing exciting.
We disconnect them from the equipment and leave them abandoned in place.
They’re not connected to the new refrigeration circuit.
They’re not carrying refrigerant.
They’re just copper buried underneath the house.
They’ve retired.
No pension.
No farewell party.
Just a quiet retirement beneath the slab.
What Happens After the New Lines Are Installed?
Installing the copper isn’t the end of the job.
The new refrigerant circuit still needs to be properly completed.
That includes things such as:
- properly connecting the new refrigerant piping
- correctly insulating the suction line
- supporting and protecting the piping
- pressure testing the completed refrigeration circuit
- verifying there are no leaks
- evacuating the system properly
- starting the equipment
- verifying refrigerant operation
- confirming the new system is performing correctly
The line set is part of the refrigeration system.
It deserves the same attention as the equipment connected to either end of it.
The Flagler Beach Verdict
Job: Complete AC system replacement.
Existing refrigerant lines: Underground beneath the home.
Could we physically remove the old lines?
Not without doing things to the house nobody wants us doing.
Did we need to?
No.
Solution: Abandon the existing underground refrigerant lines and install a new line set using an overhead attic route.
Result: New equipment connected with new, accessible refrigerant piping.
No slab demolition.
No excavation.
No treasure map showing future technicians approximately where the copper might be buried.
Just a new route.
The Bigger Lesson
When refrigerant lines disappear underneath your Florida home, you’re not necessarily stuck with them forever.
Sometimes they can be reused.
Sometimes they can be repaired.
And sometimes the best answer is:
Forget those lines. We’re going around them.
Every house is different.
We need a route that works for the equipment, the structure and the manufacturer requirements.
But if there’s a practical way to abandon problematic underground copper and install new accessible refrigerant lines?
That’s often a very attractive option.
On this Flagler Beach installation, we didn’t dig down.
We went up.
Straight into a Florida attic.
Which seemed like a brilliant idea until approximately eleven minutes after we climbed into it.