What is an inspection chamber choke?

Inspection chamber choke: what it is

PUB says private sewers, also known as sanitary drain-lines, are owned by the private premises' owners, who are responsible for maintaining them. Used water from private premises goes through these private sewers to the public sewers. So if you own a landed home, the drain line between your house and the public sewer is yours to look after.

Inspection chambers are the access points on these lines. Each one is a covered opening that lets a plumber reach the drain-line to inspect it, clear it and flush it.

An inspection chamber choke happens when something blocks the line at or near one of these chambers. Used water can no longer flow on to the public sewer, so it slows down, backs up towards the house or rises inside the chamber.

Signs of a chamber choke

In a landed home, the first signs of a choked chamber or manhole usually show up inside the house. These are practical pointers, not official rules:

• Several drains slow down at the same time, such as a shower, a sink and a floor trap.
• Water backs up into the floor trap on the lowest floor of the house.
• Water appears around the chamber cover outside, or there is a sewage smell near it.

If only one sink or floor trap is slow while the rest drain normally, the blockage may be closer to that fitting than to the chamber.

Flats are different. HDB says you maintain the sanitary branch pipes in your flat, while the Town Council is responsible for maintaining the main sanitary pipes. If you live in an HDB flat, read our guide to a main stack choke to see who handles the main pipes.

What to do first

These four steps stop the problem spreading while you arrange help.

1. Stop using the drains. Turn off taps, showers and toilets that drain to the choked line, so no more water flows towards the blockage.
2. Keep everyone clear. Keep children and pets away from an open or overflowing cover. Do not lift or open the cover yourself.
3. Note the affected drains. Write down which sinks, floor traps and toilets are slow or backing up. This helps the plumber find the choke.
4. Call a plumber. Explain what you noted and ask for the chamber and line to be cleared and flushed. Our page on choked drain clearing lists companies that offer it.

Who may clear it

PUB keeps a list of simple plumbing works that handymen may do without a PUB licence, set out on its Plumbing Works page. On the sanitary side, the list includes clearing and flushing any discharge pipe, ventilating pipe, drain-line, fitting, floor trap, inspection chamber, grease trap or pump carrying used water from a sanitary appliance to the sewerage system. So a sewer chamber blocked by a choke can be cleared and flushed by a handyman. Repairing or replacing the pipes on this line is work for a PUB Licensed Plumber.

The same list sets the limit. Repairing, replacing or altering the chamber itself, a pipe or the connection to the public sewer is not on PUB's simple works list, so it is not handyman work. Pipe repairs need a PUB Licensed Plumber, and since 2018 it has been an offence to engage a plumber not licensed by PUB for regulated works. For the private sewer itself, PUB says owners can engage a contractor or contact PUB for assistance.

PUB lists Licensed Plumbers online, and homeowners can also find them through the Singapore Plumbing Society. Before work starts, tell the company what you saw and ask whether the job is clearing only or may need a repair. Our pages on licensed plumbers and what needs a licensed plumber explain the difference.

Private line or public sewer

At a landed home, the owner deals with the private line. PUB says owners can engage a contractor to check that their private sewers are leak-free and properly connected to the public sewer, and should carry out the repairs if leaks are found. Owners can also contact PUB for assistance.

HDB flats work differently. HDB says you maintain the sanitary branch pipes in your flat, while the Town Council maintains the main sanitary pipes. HDB also says Town Councils control, manage, maintain and improve the common property of HDB residential flats. So a chamber in a common area is the Town Council's. If you live in an HDB flat, call your Town Council first, before any plumber or handyman.

The cost of clearing an inspection chamber depends on the job. Ask what a quote covers, such as flushing after clearing, and see our guide to plumbing costs.

When to stop and call a professional

Call a professional if:

• Water overflows from the chamber cover.
• Sewage backs up into the home through a floor trap or toilet.
• The choke returns soon after clearing. A pipe may be damaged, and pipe repair is PUB Licensed Plumber work under PUB's rules.
• It happens at night. Read our post on emergency plumbing at night.

Compare plumbing companies by the areas they say they cover and the prices they publish.

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