Common drain problems, explained
What your drains are trying to tell you. For each problem: what usually causes it, what you can safely check yourself, and when it's time to get someone in.
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Most drain problems give a warning before they become an emergency. Catching them early usually means a smaller, simpler fix. Jump to the problem you've got:
- A smell of drains
- Gurgling plugholes or toilets
- Slow-draining sinks, baths and showers
- Water rising in a manhole or gully
- A toilet that rises, then drains slowly
- Damp, sinking ground or cracks near a drain
- A garden that floods or stays waterlogged
- Rats near drains
- Septic tank or treatment plant trouble
Safety first
Sewage carries germs. Wear gloves if you lift a cover, wash your hands well afterwards, and keep children and pets away from open manholes. Don't climb into a manhole or chamber: gases can build up in them.
A smell of drains
Usual causes: a dried-out trap (the water seal in a U-bend on a sink, shower or floor drain that's rarely used), a loose or cracked seal around a toilet or pipe, a blockage building up, or a cracked drain letting smells out underground.
What you can check: run water into any rarely used sinks, showers and floor drains to refill their traps. Check that manhole covers sit flat and aren't cracked. If the smell is strongest outside, notice whether it's worse after rain or in dry weather.
When to call: if the smell keeps coming back, is strong outdoors near a drain run, or comes with slow drains or gurgling. A camera survey will find a hidden crack.
Gurgling plugholes or toilets
Usual causes: air being pushed or pulled through a trap because water can't flow away freely. That's usually a partial blockage further along the drain, or a problem with the vent pipe that lets air into the drains.
What you can check: does it happen when another appliance empties, such as the washing machine or bath? If several fittings gurgle, the problem is probably in the shared drain rather than one pipe.
When to call: if gurgling comes with slow draining or smells, a blockage is likely forming. It's easier to clear now than once it's full. See drain unblocking.
Slow-draining sinks, baths and showers
Usual causes: hair and soap in bathroom traps, fat and food in kitchen pipes, or scale in older pipes. If everything is slow at once, the main drain may be partly blocked.
What you can check: with one slow fitting, try a plunger, then clean the trap under the sink with a bucket underneath. Pull hair out of shower and bath wastes. We'd avoid chemical drain cleaners.
When to call: if several fittings are slow, or clearing the trap doesn't help.
Water rising in a manhole or outside gully
Usual causes: a blockage further along the drain from that manhole. If the manhole is full, the blockage is further along. If it's empty but the one before it is full, the blockage is between the two.
What you can check: lift the covers (with gloves) to see which are full and which are empty. That helps us find it quickly. Check whether neighbours are affected too. If they are, it may be a public sewer problem for Manx Utilities (01624 687687, or Freephone 0808 1624 115). Stop using water in the house to limit what backs up.
When to call: straight away, particularly if sewage is surfacing or water is getting close to coming back into the house.
A toilet that rises, then drains slowly
Usual causes: a blockage in the toilet's own pipe (often wipes or too much paper) or further down the main drain. When the main drain is blocked, a downstairs toilet or shower is often where the water shows first, because it's the lowest point.
What you can check: don't keep flushing. Try a toilet plunger. Check whether other fittings are also slow, which points to the main drain.
When to call: if plunging doesn't clear it, or other fittings are affected.
Damp, sinking ground or cracks near a drain
Usual causes: a leaking drain can wash soil away from around the pipe over time. That can leave a hollow under a path or patio, a dip in a lawn, a persistently damp patch, or in some cases contribute to movement in a nearby wall.
What you can check: notice where the damp or dip is in relation to your drain runs and manholes, and whether it changes after heavy rain or when water has been used in the house.
When to call: soon. A camera survey will confirm whether the drain is to blame, and a leaking pipe can often be relined without digging. If you're concerned about the building itself, speak to a structural engineer too.
A garden that floods or stays waterlogged
Usual causes: a rainwater soakaway that has silted up or was too small, a blocked gully or downpipe, rainwater with nowhere to go, or ground that simply drains slowly, such as heavy clay or a high water table in winter.
What you can check: watch where the water collects and where it comes from during heavy rain. Are downpipes and gullies overflowing? Does the water drain away within a day or two, or sit for weeks?
When to call: if water is getting close to the house, a soakaway is overflowing, or the problem is getting worse. We can check the soakaway and drains, test how the ground drains, and tell you what would help. See drainage fields and soakaways.
Rats near drains
Usual causes: rats live in sewers and travel along drains. A cracked pipe, an open joint or a missing cap on an old pipe gives them a way out into gardens and buildings.
What you can check: look for gnawed holes, burrows or droppings near manholes and drain runs, and for any open pipe ends.
When to call: a pest controller deals with the rats. A drain survey finds how they're getting in, so the gap can be sealed and they don't come back.
Septic tank or treatment plant trouble
Usual signs: slow toilets and drains throughout the house, smells around the tank, sewage in the last chamber, an alarm sounding on a treatment plant, or wet, spongy ground and unusually green grass over the drainage field.
Usual causes: a tank that's overdue for emptying, a blocked outlet, a failed blower or pump on a treatment plant, or a drainage field that has clogged and can no longer soak water away.
What you can check: when was it last emptied? On a treatment plant, is the air blower running and is there an alarm light? Avoid putting wipes, fats, bleach and strong chemicals down the drains.
When to call: if the tank hasn't been emptied recently, if there's sewage on the surface, or if a treatment plant alarm is on. See tank emptying and maintenance and drainage fields.
Quick answers
What should never go down a drain or toilet?
Wet wipes (including "flushable" ones), cotton buds, sanitary products, nappies, cooking fat and oil, food scraps, paint, and building materials such as grout or plaster. On a septic tank or treatment plant, also go easy on bleach and strong cleaning chemicals, which kill the bacteria the system relies on.
Is a blocked drain an emergency?
It is if sewage is coming up inside or outside the house, or water is about to come in. A single slow sink usually isn't, and you may be able to clear it yourself.
How can I find out where my drains run?
Manhole covers show roughly where the runs go. For an exact route and depth, we can trace the pipe with a camera and transmitter as part of a CCTV survey.
Related pages
Still not sure what's causing it?
Describe what's happening and we'll tell you what we think it is, and whether it needs us.