Why does my bathroom smell like sewage?

Bathroom drain smell: where it usually comes from

When a bathroom smells like sewage, start with the floor trap. HDB's floor traps guide treats foul smells as a floor trap problem, and the fixes it gives point to two common causes: particles trapped at the grating, and a floor trap left unused for a long time, for example during an overseas holiday.

The other common cause is a choke. If the smell comes with water that drains slowly or rises out of the floor trap, something may be blocking the trap. The same HDB guide links overflowing water to solid matter or grease in the trap.

Floor trap smell: what you can do yourself

Most of these fixes need only a few minutes and some water. HDB's floor traps guide gives four for foul smells: remove trapped particles and flush, flush the toilet regularly, seal the floor trap cover temporarily if it will not be used for a long time (for example an overseas holiday), and install an anti-mosquito device. To prevent chokes, the same page says to keep the grating closed and not to pour cooking oil or discard food waste or solid items down the floor trap or sink.

1. Clear the grating. Lift the grating and remove any trapped particles you can reach. Put them in the bin, not back down the drain.
2. Flush the floor trap. Pour plenty of water down the floor trap to flush it through, then put the grating back and keep it closed.
3. Flush the toilet regularly. Flush the toilet in each bathroom regularly, including one that is used less often.
4. Seal it before a long absence. If the bathroom will not be used for a long time, for example during an overseas holiday, seal the floor trap cover temporarily.

If you are going away soon, see what else to check at home before an overseas trip.

Slow drains and floor trap chokes

A smell that comes with slow draining needs more than a rinse. HDB's pipes guide says slow or no discharge of wastewater can come from wear and tear or from a choke in the floor trap caused by solid waste building up. Its floor traps guide adds that water overflowing from a floor trap means solid matter or grease is blocking it. Both pages say to remove the solid waste, and the floor traps guide says to engage a licensed plumber for serious cases.

You do not need a licensed plumber for every choke. PUB's Plumbing Works page lists clearing any blockage in any floor trap, water closet or sanitary appliance as simple plumbing works, which a handyman may do without a PUB licence.

If you would rather have someone clear it, companies in the directory publish these rates:

FROM THE HOMEZYPRO DIRECTORY

Published choke clearing rates

For the most common unit (per job), the lowest published choke clearing rates from 22 companies run from S$50 to S$150 per job (middle rate S$80), to clear one choke in a toilet bowl, floor trap or sink. The middle figure is a real published rate, not an average. Each figure is one company's own advertised rate with its conditions, not a quote.

See 22 published choke clearing rates and sources

Lowest matching advertised rate per company, in SGD as published. "From" marks a starting price and ranges are shown in full. Check the source for minimums, GST and inclusions.

Company	Service as listed	Rate	Source
Kiasu Plumber	Remove kitchen sink choke	From S$50 per job	kiasuplumber.com
SG1 Plumber Singapore	Floor-trap Choke Cleaning	S$50 per job	sg1plumber.com
AquaHero Plumbing	Clear Clogged Floor Trap	S$60 per job	aquahero-plumbing.sg
EZ Plumber SG	Clear Clogged Floor Trap	S$60 per job	ezplumber.sg
Plumber - Singapore Plumbing 24hrs	Supply Labour to Clear Toilet Bowl Choke	From S$60 per job	singaporeplumbing24hrs.com.sg
Sin Plumbing Singapore	Clear clogged floor trap	From S$60 per job	sinplumbing.com
Uncle Plumber	Clear clogged floor trap	From S$60 per job	uncleplumber.sg
GD Plumbing	Clogged toilet bowl / Clearing toilet bowl choke	From S$70 per job	gdplumbing.com.sg
Hdbplumber Service SG	Clearing toilet bowl choke	From S$79 per job	hdbplumberservice.com.sg
Ace Plumbing Specialist	Clogged toilet bowl / clearing toilet bowl choke	From S$80 per job	aceplumbing.sg
Active Plumbing Singapore	Clearing toilet bowl choke	From S$80 per job	activeplumbing.sg
Home Plumbers Singapore	Clear a toilet bowl choke	From S$80 per job	homeplumbers.com.sg
PlumbersGuru Singapore	Basic unclogging starts . Complex jobs with grease traps or root intrusion cost more. We	From S$80 to S$150 per job	plumbersguru.com
PW Plumbing Services	Toilet Choke Clearing	S$90 to S$150 per job	pwplumbing.com.sg
SR Power Plumber Pte. Ltd.	Clearing toilet bowl choke / clogged toilet bowl	From S$90 per job	srpowerplumber.com
Huat Plumbing	Toilet Bowl Choke Clearing	From S$100 per job	huatplumbing.sg
Prima Technologies Pte. Ltd. (Prima Services)	Toilet Bowl Choke Clearing	From S$100 per job	primaservices.sg
Sk Plumber	Toilet bowl choke clearing	From S$115 per job	sksplumber.com
Best Plumbing	Clogged toilet bowl / Clearing toilet bowl choke	From S$120 per job	bestplumbing.com.sg
Summer Plumbing Service	Clogged toilet bowl / Clearing toilet bowl choke	From S$120 per job	sgplumbing.com.sg
NILE Plumbing	Clear Choke (Sink/Basin)	From S$150 per job	nileplumbingsg.com
Siam Engineering Pte Ltd	Choke Clearing & Drainage	S$150 per job	siamengineeringsg.com

22 companies publish a choke clearing rate, all per job. Their published rates run from S$50 to S$150 per job, as printed. The two middle rates are both S$80 per job, so S$80 is a real published rate from one company. The scope as printed is to clear one choke in a toilet bowl, floor trap or sink. Many lines start with "From", so ask what the price includes before the visit.

For more on pricing, see the floor trap choke cost guide. If water pools in the shower area, the shower drain choke guide covers that case.

When the main stack is the problem

Not every smell starts in your own pipes. HDB's pipes guide says you maintain the sanitary branch pipes in your flat, while the Town Council is responsible for maintaining the main sanitary pipes. HDB's page on the functions of HDB Branches and Town Councils adds that you contact your Town Council about routine maintenance.

If a sewer smell in the bathroom, a choke or a slow drain seems to come from the main pipe, or your neighbours have the same problem, report it to the Town Council. Describe what you have noticed: the smell, how the water drains and which flats are affected. The main stack choke guide explains more about this case, and who maintains what in an HDB flat sets out the split between you and the Town Council.

When to stop and call a professional

Clearing the grating and flushing deals with many smells. Stop and call a professional when:

• The smell stays after you have cleared the grating and flushed the floor trap and the toilet.
• Water drains slowly or overflows from the floor trap, and removing what you can reach does not help.
• You see a leak at a pipe joint. HDB's pipes guide says to engage a licensed plumber for repairs where necessary.
• The problem lies beyond the grating and the trap, in pipes you cannot see or reach.

When you call, ask whether the price covers the floor trap only or the toilet and sink as well. To see which jobs must go to a licensed plumber, read what needs a licensed plumber. You can also compare companies that publish rates for choked drain clearing, or browse plumbing companies with the areas they say they cover.

Questions