Maybe you've just moved into a new place with mystery stains from a previous tenant's pet. Maybe it's an odour that's been part of the family home for years and nobody quite remembers where it started. Either way, old, set-in pet stains are a different challenge to fresh accidents — but they're not a lost cause.
Why Old Stains Are Harder to Treat
When urine is left untreated for an extended period, several things happen that make it more stubborn than a fresh spill:
- Uric acid crystals fully harden and bond to fibres, grout or timber, becoming more concentrated and resistant to breakdown over time.
- The contamination often spreads further than the visible stain, soaking into carpet backing, underlay, subfloor or deep into turf infill.
- Bacterial growth compounds the problem, adding a second odour source layered on top of the original urine smell.
- Repeated "masking" attempts over the years — air fresheners, scented sprays, surface cleaners — can leave behind their own residues that need to be worked through as well.
This is why an old stain often won't respond to a single spray-and-wipe treatment the way a same-day accident would.
A Realistic Approach to Old Stains
1. Confirm what you're dealing with
If you're not sure exactly where old stains are, a UV blacklight torch is a genuinely useful tool — dried urine typically fluoresces under UV light, even when there's no visible mark and no obvious smell in normal lighting. This helps you treat the full area rather than guessing.
2. Saturate, don't just spray
Older stains have often soaked well below the surface. A light surface spray won't reach deep enough. For carpet, this means applying enough smellBgone PLUS+ to fully saturate the area (including working it gently into the fibres), not just misting the top.
3. Allow proper dwell time
Enzymes need time and moisture to fully break down hardened uric acid crystals — this isn't an instant process, especially with years of build-up. Let the product sit rather than wiping it away immediately.
4. Expect to repeat the treatment
For genuinely old or heavily set-in stains, one application often isn't enough. It's common — and completely normal — to need two or three treatments over the course of a week or two before the odour is fully gone. This isn't a sign the product isn't working; it's a reflection of how much has built up over time.
5. Treat the surrounding area, not just the stain itself
Odour and contamination from old accidents often spread beyond what's visible. Treat a wider area than just the obvious mark, particularly along skirting boards, in corners, or around the edges of a stain.
For Old Turf Odour Specifically
If you've inherited artificial turf with a long-standing pet odour problem, the same principle applies but at a larger scale. smellBgone SYNTURF is a concentrated formula designed to penetrate deep into turf and infill, which is exactly where old, established contamination tends to sit. For turf with a genuinely long history of pet use, replacing or supplementing the infill with smellBgone PETFILL may also be worth considering, since old infill can become saturated with residue that surface treatments alone can't fully reach.
Managing Expectations
It's worth being upfront: very old, deeply set-in stains sometimes take persistence to fully resolve, particularly if the contamination has reached subflooring or underlay that can't be directly treated without lifting carpet. In these cases, enzyme treatment will significantly reduce odour, but a professional carpet or flooring assessment may be worth considering for truly severe, long-neglected cases.
For the vast majority of old pet stains, though, a thorough, repeated enzyme treatment gets the job done — it just takes a little more patience than a same-day spill.
Shop smellBgone PLUS+ or smellBgone SYNTURF to tackle even the most stubborn, long-standing pet odours.