A bad smell coming from your drains is never pleasant. Whether it smells like rotten eggs, sewage, damp, chemicals or something musty, the odour is usually a sign that something is not quite right within your drainage system.
Some smells are caused by simple issues, such as food waste sitting in a kitchen drain. Others can point to more serious problems, including blocked pipes, damaged drains, sewer gas, poor ventilation or a collapsed section of pipework.
In this guide, we explain what different drain smells may mean, what could be causing them and what you should do next.
My Drain Smells Like Rotten Eggs
A rotten egg smell is one of the most common drain odours. This smell is often linked to hydrogen sulphide gas, which can be produced when organic matter breaks down inside the drainage system.
In a kitchen, this may be caused by food waste, grease, fat or soap residue collecting inside the pipework. In bathrooms, it may be linked to hair, skin cells, soap scum or stagnant water.
However, a strong rotten egg smell can also suggest a deeper drainage issue, especially if the smell keeps coming back after cleaning.
What to do
Start by cleaning the affected plughole and flushing it with hot water. Avoid pouring fats, oils or grease down the sink, as these can cling to the pipework and trap food waste.
If the smell returns quickly, affects multiple drains or is especially strong, it is worth arranging a professional inspection. JDrainage can check for blockages, build-up and deeper drainage issues using drain cleaning equipment and CCTV drain surveys where needed.
My Drain Smells Like Sewage
A sewage smell is usually a sign that wastewater gases or odours are escaping somewhere they should not be. This may be caused by a blockage, dried-out trap, damaged pipe, poor ventilation or a problem further down the drainage system.
Every sink, bath, shower and toilet should have a water trap that helps stop smells from coming back into the property. If the trap dries out or becomes faulty, smells can rise from the drain.
A sewage smell may also appear when waste is not flowing away properly. If there is a blockage, sewage and dirty water may sit in the pipework, creating a strong and unpleasant odour.
What to do
If the smell is coming from a rarely used drain, run water into it to refill the trap. If the smell is coming from a toilet, shower or regularly used sink, do not ignore it.
Watch for other warning signs such as slow drainage, gurgling sounds, bubbling toilets or water backing up. These can suggest a blockage or drainage fault. JDrainage can carry out drain unblocking, high-pressure water jetting and CCTV drain inspections to locate the cause.
My Drain Smells Like Damp or Must
A damp or musty smell around drains may suggest stagnant water, trapped debris, hidden leaks or poor ventilation. In some cases, the smell may not be coming directly from the drain itself, but from damp areas around the pipework.
Bathrooms, utility rooms and kitchens are common places for musty smells because moisture is already present. If water is escaping from a damaged pipe or drain connection, it can create damp conditions that lead to unpleasant odours.
What to do
Check for visible signs of moisture, staining, mould or water damage around sinks, toilets, baths, showers and external drains. Clean the affected area and make sure the room is well ventilated.
If the smell persists, especially near walls, floors or external drainage points, the pipework may need investigating. A CCTV drain survey can help identify cracks, leaks, displaced joints or other hidden problems.
My Drain Smells Like Food Waste
A food-like smell is most common in kitchen sinks. It is usually caused by small pieces of food, grease, oil, fat, sauces or washing-up residue sticking to the inside of the pipe.
Over time, this build-up can rot, trap more debris and create a lingering smell. It can also contribute to slow drainage and eventually lead to a blockage.
What to do
Remove any food waste from the sink strainer and clean around the plughole. Flush the sink with hot water and avoid putting leftovers, coffee grounds, fat, grease or oil down the drain.
If the sink drains slowly or the smell keeps returning, the pipe may already have a build-up inside it. Professional drain cleaning or water jetting can help clear stubborn deposits properly.
My Drain Smells Like Chemicals
A chemical smell from drains can have several causes. It may come from cleaning products, paint, solvents or other substances that have been poured down the sink. In some cases, it may be caused by gases escaping from the drainage system or reactions between different cleaning products.
You should be especially careful when using drain cleaners. Mixing cleaning chemicals can be dangerous and may damage pipework if used incorrectly.
What to do
Avoid adding more chemicals to the drain. Ventilate the area and flush the drain with plenty of water if it is safe to do so.
If the smell is strong, unusual or does not clear, it is best to get professional advice. A drainage specialist can inspect the system and identify whether there is a blockage, trapped chemical residue or another underlying fault.
My Drain Smells Like Urine
A urine smell is often noticed around toilets, bathroom floors, urinals or external drains. It may be caused by residue around the toilet base, a leaking seal, poor cleaning access, stagnant wastewater or a problem with the waste pipe.
If the smell seems to come from the floor around the toilet rather than the bowl, there may be an issue with the seal or pipe connection.
What to do
Clean thoroughly around the toilet, including the base and surrounding floor. Check whether the smell returns soon after cleaning.
If it does, or if you notice leaks, dampness, movement in the toilet or slow flushing, the pipework may need checking. JDrainage can investigate drainage connections, blockages and waste pipe issues to find the source of the smell.
My Outside Drain Smells Bad
Outdoor drain smells are often caused by blocked gullies, rotting debris, standing water, fat build-up, silt, leaves or a blockage further along the drain run.
Outside drains deal with a lot, including wastewater, rainwater, mud, leaves and general debris. If they are not cleaned or maintained, smells can develop and may eventually become noticeable near doors, patios, driveways or garden areas.
What to do
Clear any visible leaves or debris from the top of the drain if it is safe to do so. Do not attempt to remove heavy covers or reach into blocked drains.
If water is sitting in the drain, overflowing or smelling strongly of sewage, call a drainage company. High-pressure water jetting can clear stubborn blockages, while a CCTV drain survey can check whether there is a structural problem.
My Drain Smells Worse After Rain
If drain smells become worse after heavy rain, the drainage system may be struggling with excess water. Rain can put pressure on drains, especially if there is already a blockage, damaged pipe, poor flow or collapsed section.
Smells after rain can also be linked to overwhelmed external drains, surface water issues or sewer gases being pushed back through the system.
What to do
Pay attention to whether the smell appears after every period of heavy rain. Look for overflowing drains, standing water, slow drainage or gurgling sounds indoors.
Recurring smells after rainfall should be inspected, as they may point to a drainage issue that will worsen over time. JDrainage can carry out CCTV surveys, drain unblocking and maintenance to identify and resolve the cause.
When Should You Call a Drainage Company?
Some drain smells can be improved with simple cleaning, but persistent or strong odours should not be ignored.
You should contact a drainage specialist if:
- The smell keeps coming back
- More than one drain is affected
- Water is draining slowly
- Toilets are bubbling or gurgling
- Wastewater is backing up
- External drains are overflowing
- The smell is strongest after rain
- You suspect a blockage, leak or damaged drain
Bad smells are often an early warning sign. Dealing with the problem quickly can prevent a minor blockage from becoming a more serious drainage issue.
Final Thoughts
Different drain smells can point to different problems. Rotten egg smells may be linked to trapped organic matter or sewer gases. Sewage smells can suggest blocked or faulty drainage. Musty smells may be caused by damp or stagnant water, while bad smells outside may indicate blocked gullies or damaged pipework.
If cleaning does not solve the issue, the next step is to find out what is happening inside the drainage system.
JDrainage provides professional drain unblocking, drain cleaning, high-pressure water jetting, CCTV drain surveys, drainage maintenance and drain repair services. Whether your drain smells like rotten eggs, sewage or something else entirely, a proper inspection can help find the cause and get your drains flowing properly again.