Whole-system duct and dryer vent check with before-and-after photos - you see exactly what came out of your vents
That "$99 whole-house special" is a bait ad - the real number appears once they are in your hallway, or the "clean" is a shop-vac at the register. We photograph the inside of your ducts before and after instead.
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Before
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Before
AfterGuardsman Duct Sealing & Repair: The San Antonio Owner’s Guide
Guardsman duct sealing and repair in San Antonio typically runs $340-$620 for a full system seal depending on duct run count and accessibility, and we stock Guardsman-compatible mastic, foil tape, and collar components on every truck. Most failing seals show up as uneven room temperatures or dust blowing from registers after the AC cycles on. We see this pattern constantly in San Antonio homes built 2015-2020, especially in Stone Oak and Alamo Ranch where flex duct was run tight through hot attics.
Which Guardsman Models This Applies To
Guardsman produces sealing hardware for two distinct system categories: rigid metal duct (galvanized steel, typically 26-30 gauge) and flexible duct (insulated flex with polymer core, common in post-2005 residential builds). The critical compatibility gotcha is collar diameter: Guardsman rigid collars ship in 6-inch, 7-inch, and 8-inch nominal sizes, but the actual inner diameter measures 1/8-inch under nominal - so a “6-inch” collar fits 5 7/8-inch duct. We’ve seen San Antonio homeowners buy nominal-size aftermarket collars that gap at the joint.
For flex duct, Guardsman uses a proprietary barbed insert design (three rows of helical barbs, 1/4-inch depth) that standard flex connectors don’t replicate. The aftermarket equivalent we carry matches this barb geometry and uses the same 50-pound tensile-rated polymer. OEM Guardsman mastic is water-based, UL 181B-M rated, with a 2-hour skin time in San Antonio’s summer attic conditions - aftermarket mastics often skin in 45 minutes, which sounds better until you’re working a long run and the bucket skins before you finish.
To identify your part: check the stamped model prefix on any existing collar. “GRD-R” indicates rigid metal hardware; “GRD-F” indicates flex. The suffix digits denote diameter. If the stamp is painted over or corroded, measure the duct inner diameter with a tape measure, not a ruler.
Signs Your Guardsman Duct Sealing & Repair Is Failing
- Uneven temperatures room-to-room. When a seal fails at a junction or collar, conditioned air leaks into the attic or wall cavity before reaching the register. The room at the end of that duct run gets whatever’s left, which in a San Antonio July means it’s 6-10 degrees warmer than the thermostat reading by mid-afternoon.
- Dust puffing from registers when the system cycles on. A failed seal creates negative pressure at the gap during blower startup, sucking attic dust and fiberglass insulation into the duct. The camera goes in first. Then we talk - and what we usually find is a gray mat of debris packed behind the register, not just surface dust.
- Energy bills climbing without rate changes. A single failed collar in a hot attic can leak 15-20% of conditioned air. In San Antonio, where cooling loads run 2,200+ hours annually, that shows up in kWh usage before you notice comfort issues.
- Whistling or rushing air sounds near ducts. High-velocity air passing through a gap smaller than a pencil eraser produces a distinct whistle. The sound localizes near the failure point, which helps us target our camera inspection.
- Musty or chemical odors when AC first turns on. Unsealed gaps pull attic air - hot, often humid, sometimes carrying rodent activity or off-gassing from roof decking - directly into your supply. San Antonio’s spring pollen season makes this particularly noticeable.
BeforeAfterReplacement Cost & What’s Included
| Scope | Typical Range | What Drives It |
|---|---|---|
| Single collar/seal repair (accessible) | $180-$280 | Duct diameter, attic access difficulty |
| Multi-point seal (3-5 joints) | $340-$480 | Run length, mastic volume needed |
| Full system reseal | $520-$620 | Home size, duct run count, plenum condition |
Every quote under Haven Standard Clause 1 is written and agreed before work starts. The price includes Guardsman-compatible or OEM parts, labor, and the documented photo record of every sealed joint. We also photograph the failure before touching it - so you see the gap, the debris pattern, and the finished seal in sequence. The 365-Day Done Right Promise covers labor and materials; if a seal we addressed fails within that window, we return and make it right at no charge.
CleanRun Air Duct Cleaning San Antonio is an independent service provider, not affiliated with Guardsman. We source parts through recognized HVAC wholesalers and verify compatibility against your existing system before quoting.
DIY or Call Us?
What you can safely check yourself: walk your accessible duct runs with a flashlight and look for disconnected collars, tape that’s peeled or browned, or mastic that’s cracked and powdery. Note the locations. This is useful information to hand any technician.
Where DIY goes wrong: attic flex duct in San Antonio attics reaches 140°F+ in August. The polymer becomes pliable and easy to crush. A homeowner stepping near a run, or pulling with normal hand pressure, can collapse the inner core and create a restriction worse than the original leak. Mastic application looks simple but requires negative-pressure extraction (suction that pulls fumes and overspray away from living space) to meet indoor air quality standards - a shop fan in a vent won’t do it. And without a camera scope, you can’t verify the seal integrity at the back side of the joint.
We’re not going to tell you it’s dangerous to touch. It is easy to make worse. If you’ve found the failure point, call (726) 600-7155 and we’ll scope it, quote it in writing, and fix it with a photo record of the result.
FAQs
How long do Guardsman duct seals last in San Antonio?
A properly installed Guardsman collar and mastic seal lasts 15-20 years in San Antonio’s climate, but attic temperatures above 130°F accelerate polymer fatigue. We typically see first failures at 8-12 years in homes with dark shingle roofs and minimal attic ventilation. Call (726) 600-7155 if you’re in that window and want a scope inspection.
Can a failing seal be repaired instead of replaced?
Tape-over repairs fail within one to two seasons; the adhesive degrades in heat cycles and the underlying gap remains. We remove failed material, clean the joint to bare metal or polymer, and install new hardware. That’s the only repair we warranty. Call (726) 600-7155 for a written quote on proper replacement.
How long does a Guardsman seal replacement take?
A single accessible collar takes 45-90 minutes including setup, camera documentation, and cleanup. A full system reseal on a 2,500-square-foot San Antonio home runs 4-6 hours. We schedule morning starts to avoid peak attic temperatures. Call (726) 600-7155 to check availability.
Do you stock Guardsman parts on the truck?
We stock Guardsman-compatible collars in 6-inch, 7-inch, and 8-inch rigid and flex configurations, plus UL 181B-M mastic and foil tape rated for San Antonio attic conditions. Same-day completion is standard for single-point repairs identified during morning inspection. Call (726) 600-7155 to confirm stock for your specific diameter.
CleanRun also stocks parts for Lennox, Trane, and Carrier systems - we carry the full compatibility range for major residential HVAC brands.
Written by Tomas Reyes, Owner, CleanRun Air Duct Cleaning San Antonio at CleanRun Air Duct Cleaning San Antonio, serving San Antonio and nearby areas.