Drainage problems rarely announce themselves politely. More often, they show up as a faint damp patch that never quite dries, a downstairs loo that “sometimes” struggles, or that persistent gurgle in the kitchen sink you’ve learned to ignore. The tricky part is that the visible symptom is often nowhere near the real fault. A slow-draining shower might be linked to a partially collapsed pipe run outdoors; a recurring smell could be a failed trap seal caused by negative pressure elsewhere in the system.
That’s why drainage specialists approach investigations like detectives. They don’t just clear a blockage and move on—they work out why it happened and whether it’s likely to happen again. In many cases, the fastest way to avoid repeat call-outs is to bring in a team that can survey, trace, and test the network properly. Firms such as FloWise (and other reputable specialists) typically combine multiple diagnostic tools—CCTV, tracing, flow testing, and more—to pinpoint hidden defects without guesswork or unnecessary digging.
So what are the steps behind a professional diagnosis, and how do experts decide on the best fix? Let’s break down the process.
The tell-tale signs that the problem is “hidden”
A straightforward blockage inside the home is usually obvious: one fixture backs up, and a quick trap clean might solve it. Hidden drainage issues are different because they tend to be intermittent, widespread, or weather-dependent.
Symptoms specialists take seriously
Professionals tend to look for patterns such as:
- Repeated blockages in the same line, even after clearing
- Slow drainage across multiple fixtures, especially on lower floors
- Bad odours that come and go (often linked to ventilation or trap issues)
- External ponding after rainfall, soggy patches, or unexplained subsidence
- Rodent activity near inspection chambers (broken pipes can become entry routes)
- Gurgling noises that suggest pressure imbalance in the pipework
That list isn’t meant to make you paranoid—it’s to highlight that “minor” annoyances can point to structural or design issues. The earlier they’re identified, the less disruptive (and expensive) the fix usually is.
How specialists pinpoint the real cause (without tearing everything up)
Modern drainage investigation is a blend of traditional know-how and high-quality diagnostics. The best operators start with the basics—layout, levels, and flow direction—then use targeted tools to confirm what’s happening underground.
Step 1: System mapping and a proper site assessment
Before any camera goes in, a specialist will typically check:
- Location and condition of inspection chambers and rodding points
- Whether the property has combined or separate foul and surface water systems
- Recent changes: extensions, driveway works, landscaping, new appliances
- Obvious risk factors like large trees, known clay soils, or historic ground movement
This matters because drainage failures are often triggered by changes around the system—roots seeking moisture, a newly paved area altering runoff, or an extension tied into an old line that was already marginal.
Step 2: CCTV drain surveys (and what “good” looks like)
CCTV surveys are the workhorse of drainage diagnosis, but the real value is in interpretation. A skilled surveyor doesn’t just spot a blockage; they look for indicators of why it formed.
Common findings include:
- Root ingress at joints (often a recurring issue unless the entry point is repaired)
- Deformed or “egg-shaped” pipes from ground pressure, especially older clay runs
- Open joints and displaced sections that catch debris
- Fat, scale, or silt build-up that suggests poor gradient or low flow velocity
- Construction debris (not uncommon after building work)
Good reporting should include clear footage, defect coding, and practical recommendations—not just “pipe damaged” with no context.
Step 3: Tracing, dye testing, and smoke testing
When symptoms don’t match the obvious route, specialists use tracing techniques. Dye testing can confirm where water is actually going (useful for mysterious damp areas or suspected cross-connections). Smoke testing helps locate broken vent lines, faulty seals, and hidden openings where odours escape—particularly in older properties with complex alterations.
Step 4: Flow and pressure behaviour
Drainage isn’t just about what you can see on camera. Professionals also consider behaviour under load: what happens when multiple appliances discharge at once, or when there’s heavy rainfall? A line that looks “mostly fine” may still be functionally inadequate due to poor falls, partial backfalls, or surcharging during peak flow.
Choosing the right fix: clearance vs repair vs redesign
Once the root cause is clear, the solution becomes a decision about longevity, cost, and disruption. A responsible specialist will explain the trade-offs instead of defaulting to the biggest job.
Clearance methods: fast, but not always enough
For many blockages, high-pressure water jetting is the fastest way to restore flow. It’s effective for silt, grease, and general debris, and it can be paired with descaling tools for stubborn deposits.
However, if there’s a structural defect—like a cracked pipe or a displaced joint—jetting is a reset, not a cure. The blockage will often return because the underlying snag point remains.
Targeted structural repairs (often minimally invasive)
Where there’s localised damage, specialists may recommend:
- Patch lining for small cracks or joint defects
- Full-length lining (cured-in-place) for longer runs with multiple defects
- Excavation and replacement for collapsed sections or severely misaligned pipes
Lining can be a smart option when access is difficult (under a conservatory, patio, or driveway). But it’s not suitable for every scenario—pipe condition, diameter, and deformation levels all matter.
When the “problem” is actually design
Some issues aren’t damage at all—they’re design limitations that have become apparent over time. Examples include undersized surface water drainage on modern paved areas, or old combined systems struggling with heavier rainfall patterns. In those cases, solutions might involve:
- Adding or resizing gullies and channels
- Installing or upgrading soakaways (subject to ground conditions)
- Incorporating SuDS-style measures to slow and store runoff
- Correcting gradients where feasible to improve self-cleansing flow
A redesign sounds dramatic, but sometimes a small reconfiguration prevents years of recurring call-outs.
Preventing a repeat: what good specialists advise
Once the immediate issue is solved, prevention is where real value sits. Practical guidance tends to be refreshingly simple: don’t treat drains like bins, keep an eye on what changes around the property, and act early when symptoms start.
If you’ve had a serious problem—roots, collapse, repeated backups—ask for evidence (video, photos, defect notes) and a clear maintenance plan. For some properties, periodic jetting or an inspection schedule is sensible; for others, a one-off repair is enough.
Hidden drainage issues can feel mysterious, but they’re rarely unsolvable. With the right investigation, you move from “it keeps happening” to a clear diagnosis and a fix that matches the real cause—whether that’s debris, damage, or a system that needs to be brought up to modern demands.
