Typhoon Noul has passed, but that's when village-house septic tank backflow begins. If you catch a foul smell, sewage surging back when you flush, or water welling up from the floor drain, your septic tank has likely overflowed — stop using water, take photos to record it, and get a licensed drainage company to inspect the tank.
Noul struck Hong Kong on 25–26 July 2026, with the No. 8 signal hoisted at one point. The Drainage Services Department confirmed 8 flooding reports this time, concentrated in the rural New Territories. This piece focuses on the village-house septic tank; for the immediate 5-step response to general sewage backflow, see our guide "Sewage Backflow: What to Do? A Rainy-Season Self-Help Guide".
Where are the 8 flood spots after Noul?
According to hk01 and news.gov.hk (26 July 2026), the DSD confirmed this round's 8 flooding reports were concentrated in the rural New Territories, at these locations:
- Tam Shui Hang, Sha Tau Kok Road
- On Po Tsuen, Fan Kam Road
- Tung Tsz Tsuen, Tai Po
- Shek Wu Wai, San Tin
- Po Kak Tsai Tsuen, Fanling
- Kiu Wong Street, Ping Shan
- Tai Po Tin, Ping Che
- New Praya, Kennedy Town
These spots are exactly the dense clusters of village houses that rely on septic tanks and aren't connected to public sewers — in other words, the area Motion Waste sends its trucks to every day. Heavy rain makes the groundwater level rise sharply; the septic tank can't drain and gets flooded by outside water, so sewage surges back out from the lowest floor drain inside the house.
What warning signs can you spot yourself before backflow?
You don't need to wait until the whole house is full of foul water to know something is wrong. Before and after heavy rain, watch for these three signals:
- Foul smell: a persistent odour around the home or the garden septic tank, more obvious after rain, means the tank is full and gas is pushing back up.
- Backflow on flushing: after flushing, the sewage won't drain away smoothly, or even surges back and the toilet water level rises abnormally — the downstream is jammed.
- Water welling from the floor: with no tap running, the toilet or kitchen floor drain seeps or wells up water — the clearest stage of backflow.
Hit one of these signals and you should arrange an inspection; hit two or more and the tank has most likely overflowed — don't drag it out.
Steps: an owner's immediate self-help checklist
- Stop using water immediately — don't flush or turn on taps, to reduce the volume of sewage.
- Move valuables and appliances off the floor, and cut the power in the affected area to avoid electric shock.
- Wear a mask and gloves, open windows to ventilate, and never touch foul water with bare hands.
- Take photos and note the time and location, to make it easier to describe to the drainage company and insurer later.
- Contact a licensed drainage company to come and inspect the septic tank and downstream drains. For the detailed emergency steps, see "Sewage Backflow: What to Do? A Rainy-Season Self-Help Guide".
Don't assume it's over just because Noul has passed
The Hong Kong Observatory said a trough of low pressure would bring more heavy rain to southern China in the middle of this week — so the risk isn't over. Village houses already flooded may still have septic tanks that haven't recovered, and a few more downpours could set off backflow again. Get an inspection and pumping done while the weather eases, rather than being caught out by the next rainstorm.
Why sign a half-yearly plan instead of scrambling for someone each time?
The EPD's guidance on village-house sewage discharge states that a septic tank must be inspected at least every 6 months, and the sludge removed once it exceeds 30cm. In other words, a septic tank overflow is never sudden — it's a "due for pumping" that nobody dealt with. Rather than scrambling for someone after a rainstorm and queuing up, sign a half-yearly maintenance plan: an inspection every six months plus pumping as needed keeps the overflow risk outside your door.
FAQ
Q: How often should a septic tank be inspected and pumped? Under the EPD's village-house sewage discharge guidance, it should be inspected at least every 6 months, and the sludge removed once it exceeds 30cm; shorten the cycle for houses with more occupants or that are rented out.
Q: Why must a DSD-registered company pump the septic tank? Septic tank sludge is a regulated residential liquid waste, and the company handling it must be registered with the DSD to be legally qualified to dispose of it — you can check the list on the DSD's official website.
Q: Noul has already passed — do I still need an inspection? Yes. The Observatory says southern China still faces heavy rain in the middle of this week; septic tanks in already-flooded village houses may not have recovered, and more rain could trigger backflow again, so inspecting before the rain is the safest bet.
Motion Waste Management Limited (Drainage Services Department (DSD) registration number P0038) has served village houses across Hong Kong since 1992, specialising in septic tank pumping, backflow handling and downstream drain clearing. If you suspect backflow after Noul, describe the situation and location straight away via WhatsApp or the quote form — we assess first then quote, with transparent charges; we also welcome enquiries about a half-yearly maintenance plan, sparing you the scramble to find someone after each rainstorm.