Monsoon plumbing in Nellore: drains, backflow and sewer smell

From October to December the north-east monsoon drops more rain on Nellore than the rest of the year put together, and the plumbing complaints change overnight: floor traps that bubble, ground-floor bathrooms that fill from below, a sewer smell that comes and goes with the rain, and sumps that turn muddy. Almost all of it is one thing — the drains outside the house are full, so the drains inside have nowhere to go — and almost all of it is either prevented in September or endured until the rain stops. Very little of it is fixed by a plumber on the day.

Why it happens

A house drain relies on gravity and on the street or building drain being lower and emptier than your pipe. In heavy rain the outside drain fills, often mixed with stormwater in older parts of the city and in low-lying and coastal areas. Water then stands in the line up to the level outside. At best your drains run slowly. At worst, water rises through the lowest opening in the house — usually a ground-floor trap — and sewer gas is pushed up every trap not sealed with water.

Sewer smell: the dry-trap problem

Every floor trap, basin waste and sink waste has a water seal that blocks drain air. A bathroom nobody uses for a month — a guest room, the terrace wash area — dries out in Nellore heat, and the seal is gone. Normally you do not notice. When rain pressurises the drain, the smell comes straight up that dry trap.

Fix: pour a bucket of water into every trap and basin in the house, including the ones in rooms you do not use. Repeat every couple of weeks through the season. If the smell persists with wet traps, it is either a trap that was never fitted (some older bathrooms have a plain pipe into the floor), a cracked trap under the floor, or a blocked vent pipe on the stack — all a plumber's job, and the vent is the building's.

Backflow into ground-floor bathrooms

If water rises in a ground-floor trap when it rains hard, the outfall is under water. Nothing inside the flat fixes that on the day. What helps:

• A weighted cover or plate over the trap grating while it is bad, to slow the rise.
• Using as little water as possible until the rain eases — the less you put in, the less comes back.
• Longer term, a non-return (backwater) valve on the building's outlet to the street drain. That is an association decision and a plumber's job at the chamber, and the only real answer in streets that flood every year.

If sewage rises in the trap without rain, that is a block, not backflow; see our blocked-drain guide.

Before the monsoon: an hour in September

1. Terrace outlets. Clear leaves and cement bits. A blocked terrace outlet turns the roof into a tank and finds the weakest joint in the slab.
2. Rainwater down pipes. Run a hose; if water backs up, snake it. Check the shoe at the bottom is not full of silt.
3. Every floor trap. Lift, clean, refit, pour water.
4. Inspection chambers. Lift the lids in your compound. Silt, roots, a slow flow — get them cleaned now. The single best thing an apartment association can do in September.
5. Sump lid and walls. A loose lid or a crack lets runoff in, and runoff carries whatever was on the road. A muddy sump in November is usually a lid, not the bore.
6. Overhead tank lid. Same logic; rain carries dust into an open tank.
7. Gully traps and compound drains. Clear the grates. Cut back the plant growing over them.
8. Motor and electrics. Is the starter box and socket out of the splash? Is the outdoor socket covered? A starter box in the open is how the monsoon takes out motors.

During the season

Keep a plunger, a bucket and gloves where you can find them. Do not pour acid into a slow drain in the monsoon; the water is standing in the line and the acid sits in your trap. If a trap bubbles when the neighbour uses water, tell the association — that is the shared line.

Humidity through these months also shows up every slow leak: a joint that dried by itself in April now keeps a patch of wall damp for weeks. Look under sinks and behind the geyser monthly.

What is yours and what is the building's

Yours: your traps, your fixture wastes, your branch lines to the stack, your sump lid, your terrace outlets if you own the roof. The building's or the owner's: the stack, the vent, the inspection chambers, the outlet to the street, any backwater valve. The municipality's: the street drain. Knowing which before you book saves a visit charge on a problem a plumber at your end cannot touch.

What it costs

Clearing traps, pouring water into dry ones, clearing terrace outlets — that is yours, and free. A blocked-drain call on our rate card is ₹399 for snaking, jetting where possible and a trap clean. A plumbing visit is ₹299 plus labour for tracing a smell or fitting a missing trap or backwater valve, parts at MRP and shown first.

When to call

A smell that stays with every trap wet; a trap that bubbles with no rain; a ground-floor bathroom that backs up every time it rains (for the building to fit a backwater valve); water through a ceiling during rain (the terrace outlet or a slab joint); and a sump that turns muddy (a cracked wall or a lid that needs re-seating).