Cornwall has one of the highest concentrations of holiday lets in Britain, and a large share of them — coastal cottages, barn conversions, moorland hideaways — sit on septic tanks rather than mains drainage. That combination has a failure mode every experienced owner knows: the tank that was "fine last year" backing up in the second week of August with guests in the house.
Why holiday lets fill tanks so much faster
- Occupancy spikes. A 6-guest let at 90% summer occupancy puts two to three times the load of a normal household through the same tank. A tank sized for annual emptying under family use can need emptying every 3–6 months under holiday load.
- Guests don't know they're off-mains. Wipes, sanitary products and cooking fat go down the drain because nobody told them not to. These are the top causes of blockages and soakaway damage in Cornish lets.
- Nobody's watching the tank. Owners are often up-country, and cleaners aren't checking sludge levels between changeovers. Problems announce themselves mid-stay instead of being caught early.
How Cornwall owners handle it
| Approach | What it looks like |
|---|---|
| Pre-season empty | Tank emptied March–April before bookings ramp up. The single highest-value visit of the year. |
| Changeover-day scheduling | Tanker visits between departure and arrival — guests never see it. Book these slots ahead; Fridays and Saturdays go first. |
| Mid-season check | For high-occupancy lets: a quick level check (or second empty) in July–August heads off the classic peak-season backup. |
| Guest-proofing | A polite bathroom notice ("we're on a septic tank — nothing but loo roll, please"), a kitchen fat trap, and bins in every bathroom. |
The cost of getting it wrong
A routine planned empty costs £150–£300 (see the full Cornwall price guide). A mid-stay backup costs an emergency callout plus whatever the ruined stay costs you — refunds, relocation, and the review that mentions sewage. Owners who've had one August emergency become permanent advance-bookers.
Compliance matters more for lets
Your septic system must meet the General Binding Rules — and for a business asset (which a holiday let is), non-compliance carries more risk than for a private home: it surfaces in property sales, insurance claims and, increasingly, letting-agency onboarding. Run through our 5-minute compliance checklist to see where you stand — most owners pass; the ones who don't are usually one fixable item away.
Where we cover
The whole county — with specialists used to holiday-let work in the main hotspots: St Ives & Carbis Bay, Newquay & Mawgan Porth, Wadebridge, Rock & Polzeath, St Austell, Mevagissey & Charlestown, Falmouth & the Helford, and the Lizard.
Get it sorted before peak season peaks
Tell us the property, rough occupancy, and when your changeover days fall — we'll match you with a licensed local specialist who works around holiday lets as standard. Request a free quote and you'll usually hear back the same working day.