Unsealed Plumbing/Drains through Slabs
Where plumbing and drain lines pass through a concrete slab without proper sealing, a concealed pathway exists for subterranean termites to enter the building structure above, bypassing any chemical or physical barrier installed at the perimeter. Our inspectors flag this in 8.72% of all reports. Unlike a visible conducive condition, the risk here is invisible without invasive inspection - the gap between pipe and slab is often concealed by floor coverings, making it undetectable during a standard visual inspection unless specifically sought.
Severity rationale
Of 677 observations, 550 (81.2%) scored 3 and 85 (12.6%) scored 4, giving a mode of 3 and an average of 3.06. No observations scored 1 and none scored 5. The 42 severity-2 findings (6.2%) represent cases where a compensating termite management system is in place or the penetration is partially accessible. The score rises to 4 when the building has no active termite management system, penetrations are completely inaccessible, or the termite-management notice is absent - conditions where the risk of concealed ingress cannot be mitigated without invasive work.
Causes
- Gap left between pipe penetration and slab opening during construction, not filled with sealant or foam
- Original sealant applied at construction has shrunk, cracked, or debonded as the building settled
- Plumbing added or modified post-construction without reinstating slab penetration seals
- Construction type (concrete slab-on-ground with in-slab plumbing) creates inherent penetration risk that is difficult to inspect retrospectively
- Absent or expired termite management system that relied on the slab perimeter as the primary barrier
Symptoms to look for
- Slab penetrations for pipes not visible as sealed - gaps around pipe collars at inspection pits, wet areas, or laundries
- No evidence of sealant, foam, or termite-rated collar around pipe penetrations at the slab surface
- Termite-management notice (AS 3660.1) does not describe a sub-slab reticulation or collared-pipe system
- Inspector unable to confirm sealing status due to floor coverings obscuring penetrations
- Termite activity or lead detected in areas immediately above slab penetrations
Remedies
- Engage a licensed pest inspector (AS 4349.3) to conduct a full inspection specifically targeting slab penetrations and identify any active termite ingress
- Engage a licensed plumber to expose and seal all accessible pipe penetrations with an approved termite-rated sealant or collar product
- Where penetrations cannot be accessed without lifting floor coverings, consider installing a perimeter reticulation system as a compensating measure - engage a licensed termite management contractor
- Establish or renew an annual termite inspection program (AS 3660.2) to provide ongoing monitoring given the inherent uninspectability of in-slab plumbing
Where we see this most
These suburbs show the highest concentration of unsealed plumbing/drains through slabs in our inspection data (minimum five observations). Click a suburb to see its full defect profile.
Worth asking our inspector about this specifically.
This defect does not require pre-settlement action in most cases, but an annual termite inspection should be confirmed as part of ongoing ownership. If no termite management system is in place and penetrations are unverifiable, engage a licensed termite contractor to assess compensating measures before the first wet season.