Smell from a little-used bathroom

Introduction

A bathroom shut for days can smell of the drain even when the tap runs away at once. The smell leaves the basin, bidet, shower or floor waste when you come back. It is not kitchen grease and it is not mould on the silicone.

How to tell it apart

Smell one hole at a time, the others covered with a damp cloth. If it leaves a single fitting and fades after you pour water in, that trap was empty.

If the basin still smells, look at the overflow, the small hole under the rim. That channel lets air out even when the trap is full.

If only the WC smells, look at the seal at the base and the connector. Do not unbolt the pan. A dry, loose seal, or air you can feel, is not the bidet.

Several fittings, the landing, or another flat: the stack or the vent, not your trap. Water sitting in the tray: a slow drain. Marks on the silicone of a windowless bathroom: IgroCasa, not a drain cleaner.

Likely causes

• A dry trap on a little-used bidet, shower, basin or floor waste.
• A dirty basin overflow that smells even with the trap full.
• A WC seal or connector that does not close.
• A stack vent that is not working, with smell from several wastes or other flats.
• A film left after hair or soap: water is not enough, so you clean by hand, not with acid.

What to do now (€0)

1. Pour water into every little-used waste. A litre or two in each hole refills the trap. If a washing machine in the bathroom has sat idle, run one drain.
2. Shut the door, wait, open it and smell. If the smell has gone, add nothing.
3. If it stays at the basin, pour a little water into the overflow and see if the smell comes from there.
4. At the WC look only at the seal and connector you can already see. If you feel air, stop. Do not pull the pan.
5. If the smell is in several rooms or on the stair, stop pouring and note which holes smell.

A small DIY step

1. Only if the smell remains and the trap is in the open: a bowl underneath, undo the unions by hand, empty, rinse, refit. Do not force a union that will not turn.
2. Check the plug washer, run the water and watch for drips.
3. If the bathroom will sit empty, a liquid trap seal holds the water in. It is not a room spray and it does not repair the stack.
4. A cracked trap is replaced after you measure the outlet, not wrapped. The cards, when the quiz shows them, are category examples, not an order.

Mistakes to avoid

• Covering the smell with spray or scented discs: the trap stays empty.
• Pouring a drain cleaner into a waste that already runs. It is not blocked.
• Mixing bleach with another product, or reaching for an acid.
• Unbolting the WC without the pan’s model.
• Switching on a dehumidifier for a drain smell.

When to call a professional

A plumber if, with the traps full, the smell returns from one fitting, or the WC seal and connector will not hold.

The building manager and a plumber if it is on the stair, in other flats, or from several wastes. If the waste is also slow, continue on a slow drain.

Safety

If the smell is gas rather than a drain, do not light a flame and do not flip a switch. Open the windows, close the meter tap if you can reach it, leave, and call the distributor’s emergency number on the bill, or 112 if there is danger. Gas and the boiler: a qualified technician, not DIY.

Do not mix bleach with ammonia or with acids and descalers. Gloves, air, the label, stop if you smell fumes. Acids and vinegar do not go on marble or natural stone. Widespread mould that returns, or someone with breathing trouble or who is frail: a technician for the damp and, for health, a doctor. A windowless bathroom is on IgroCasa.

Questions people ask