Bathroom Drain Odour Fix Hong Kong｜浴室去水臭味專業處理

A bad smell coming from the bathroom floor drain, shower trap or wash basin is one of the most common plumbing complaints in Hong Kong flats — especially in older buildings (pre-1990s) and units on lower floors where the building's main soil stack runs close to the unit. The odour is usually sewer gas (hydrogen sulphide, ammonia) that has bypassed the water seal (隔氣) inside the floor drain or U-trap.

DrainFix HK diagnoses and fixes bathroom drain odour across Hong Kong Island, Kowloon and the New Territories. From HKD 800 for a standard trap repair or re-seal, with a written WhatsApp quote before we arrive and an on-site water-flow re-test before we leave. 24-hour emergency service available.

Common causes of bathroom drain smell in HK flats

The water seal inside the U-trap (隔氣) under the floor drain or basin is what blocks sewer gas from coming back into your bathroom. When that seal fails, the smell returns. The five most common causes we see in Hong Kong are:

• Dried-out floor drain trap — floor drains in guest bathrooms, laundry areas or balconies that are rarely used lose their water seal through evaporation. Often the simplest fix: pour a cup of water into the drain weekly.
• Broken or leaking waste pipe — old cast-iron or PVC waste pipes behind false ceilings crack with age; sewer gas escapes through the crack. Usually shows up with a damp stain on the ceiling or wall.
• Missing or wrongly-installed trap — some renovation jobs skip the trap to save space, or install two traps in series ("double trap"), which siphons the seal dry.
• Blocked building vent pipe (通風管) — the soil-stack vent to the rooftop gets blocked by nests or debris; pressure pushes gas back through your traps.
• Main soil stack partial blockage — sewage sits in the stack near your floor; smell comes out of multiple drains at once.

For the full breakdown of the seven most common sources (in Cantonese), see our guide: 屋企成日聞到渠味？7大臭味源頭+解決方法.

What DrainFix HK does on-site

1. Visual + smell inspection of every bathroom drain, basin and floor drain to locate the source.
2. CCTV drain camera check if a broken pipe or hidden blockage is suspected (no wall-breaking needed).
3. High-pressure water jetting of the affected waste pipe to clear biofilm, hair and grease build-up that feeds odour.
4. Trap repair or replacement — re-seal, replace dried/broken U-trap, install anti-evaporation floor-drain insert.
5. On-site water-flow re-test — we run water for 2 minutes and confirm the smell is gone before we pack up.

See our 5-minute customer checklist for what to prepare before the technician arrives.

Pricing & turnaround

Most bathroom odour jobs are completed within 60–120 minutes on-site. Typical price range:

• Floor drain re-seal / trap water top-up + bio-clean: HKD 800–1,200
• U-trap replacement (standard PVC): HKD 1,000–1,800
• High-pressure jet of bathroom waste pipe: HKD 1,200–2,000
• CCTV inspection (if broken pipe suspected): HKD 800–1,500

Exact price is confirmed by WhatsApp before we dispatch — never any on-arrival mark-up. Full pricing logic in our 30-question FAQ.

FAQ — bathroom drain smell in Hong Kong

Why does my bathroom floor drain smell even when nothing is blocked?

In most HK cases the floor drain trap (隔氣) has dried out — the water seal that blocks sewer gas has evaporated because the drain is rarely used. Pour 1 cup of water into the drain; if the smell clears within an hour, that was the cause. Repeat weekly, or ask us to install an anti-dryness floor-drain insert (around HKD 500 fitted).

Is bathroom drain smell dangerous?

Sewer gas (mainly hydrogen sulphide and methane) is unpleasant and, at the low concentrations found in homes, mostly a nuisance. However, long-term exposure can cause headaches and nausea, and methane is flammable. If you smell a strong "rotten egg" smell in multiple drains at once, the main soil stack may be blocked — call us the same day.

Can I fix it myself with bleach or drain cleaner?

Bleach masks the smell for a day or two but does not fix the underlying cause (dried trap, broken pipe, vent blockage). Acidic drain cleaners can also damage old cast-iron pipes common in pre-1990s HK buildings. If the smell returns within a week of DIY treatment, the cause is structural and needs a technician.

Do you serve my district?

Yes — all 18 districts of Hong Kong: Hong Kong Island (Central, Wan Chai, Causeway Bay, North Point, Shau Kei Wan, Chai Wan, Aberdeen, Stanley), Kowloon (Tsim Sha Tsui, Jordan, Yau Ma Tei, Mong Kok, Prince Edward, Sham Shui Po, Kwun Tong, Wong Tai Sin, Kowloon City, San Po Kong) and the New Territories (Tsuen Wan, Kwai Fong, Tsing Yi, Tuen Mun, Yuen Long, Tin Shui Wai, Tai Po, Sheung Shui, Fanling, Sha Tin, Ma On Shan, Tseung Kwan O, Tung Chung, Discovery Bay). 24-hour dispatch.

Will you need to break the wall or floor?

Almost never for odour jobs. We use CCTV to inspect hidden pipes through the drain opening itself, and most fixes (re-seal, trap replacement, jetting) are done from the existing access points. If a pipe is genuinely broken behind a wall, we will show you the CCTV footage first and quote the repair separately — never any surprise demolition.

Related services & guides

· 7 causes of drain smell in HK homes (Cantonese guide)
· Floor drain smell — what it means and how to stop it
· Customer checklist before we arrive
· Full 30-question drain unblocking FAQ
· General blocked drain service