Festive Season Septic Tank Overload: The Smell That Ruins Christmas

Why septic tanks fail at Christmas, every single year

If you have a holiday house in Hermanus, Cape St Francis, Kosi Bay, Hluhluwe, or any of the hundreds of smallholdings around SA on septic, the system is sized for two to four people, occasionally. Then in mid-December, eight to twelve people arrive for two weeks. Hot showers double. Toilet flushes triple. The dishwasher and washing machine run every day.

A correctly sized 4 500-litre septic tank can hold roughly 24 hours of normal household waste. With four extra people, you're past that in 12 hours. By day three, solids enter the soakaway, and the soakaway begins to fail — sometimes permanently.

The smell starts on day five. By day seven you're calling every plumber in the district, none of whom can come because every other holiday house has the same problem.

What "failure" actually looks like

• Slow draining from showers and basins, then complete refusal.
• Gurgling from the lowest-set fixture (usually a downstairs shower or floor drain).
• Sewer smell in the garden, especially over the soakaway area.
• Lush, dark-green grass in patches over the soakaway (effluent is fertilising it).
• Eventually, black water seeping up through the lawn.

Before the family arrives — the 1 December checklist

1. Have the tank pumped. Book it now. Honeysuckers in coastal towns are booked solid from 15 December.
2. Check the inspection chamber between the house and the tank. It should be empty and dry.
3. Test every toilet's flush volume — make sure dual-flush mechanisms are working on the half-flush.
4. Inspect the soakaway — if there's any standing water above it, it's already saturated. Call before guests arrive.
5. Print a "septic house rules" sheet for the bathroom door (more below).

The septic house rules (laminate this)

• Nothing but toilet paper, ever. Not "flushable" wipes. Not tampons. Not cotton wool. Not dental floss.
• No oils, fats, or food scraps down the kitchen sink. Wipe pans with paper first.
• No bleach-based cleaners. They kill the bacteria the tank needs.
• Half-flush whenever possible.
• Stagger showers — don't run three showers, the dishwasher and the washing machine in the same hour.
• No long showers. 4 minutes max.

If it's already failed

• Stop using the system immediately — every flush makes it worse.
• Call a honeysucker / vacuum tanker, not a plumber. The plumber comes after.
• Don't add yeast, enzymes, or "tank rescue" sachets when the system is in failure — they don't help and waste time.
• If the soakaway has collapsed, the only real fix is a second soakaway or a new french drain — that's a January job, not a December one.

Long-term fix

If you let the property to guests during peak periods, your septic system is undersized for the use case. Upgrade to:

• A larger tank (7 500 L+).
• A two-chamber septic with effluent filter.
• A proper sized soakaway designed for peak (not average) load.
• A dosing pump that releases effluent in timed pulses rather than dumping it.

The COC-equivalent for a new septic install in coastal municipalities now often requires a registered plumber and a soil percolation test. Don't let an unregistered contractor do it.