6 Signs Your Drain Is Blocked
By Alton Facility Services • Reviewed by AFS technical team • Updated July 2026
Practical AFS Advice
This guide is written for homeowners, facilities managers, rural properties and commercial sites dealing with drainage, pump or wastewater questions. It explains the practical signs to look for, the risks of leaving faults unresolved and when to arrange a professional inspection.
For urgent blocked drains, pump alarms, sewage treatment plant faults or wastewater overflows, call 0808 196 6005 and the AFS team will help you decide the next step.
Blocked drains rarely happen without warning. In most cases, there are early signs before the problem becomes serious.
Catching the symptoms early can help you avoid flooding, bad smells, sewage backup and unnecessary repair costs.
This guide explains the six most common signs your drain is blocked, what may be causing it, and when to call a drainage professional.
Local Guidance
Practical Drainage Advice for Hampshire, Surrey, Guildford, Woking, Farnham and Basingstoke
This guide is written for properties across Hampshire, Surrey, Guildford, Woking, Farnham and Basingstoke where drainage, pump and wastewater issues often depend on access, pipe layout, ground conditions, system age and maintenance history. The aim is to help you understand what to check first, when a simple fix may be enough and when a professional inspection is the safer route.
The same symptom can be caused by several different issues, including blocked drains, drain unblocking, CCTV drain survey, drain repairs and high-pressure jetting. For that reason, recurring problems should not be judged on the first visible sign alone. A proper site check, survey, service visit or fault diagnosis can prevent repeated callouts and reduce the risk of unnecessary repair work.
If you are comparing options or costs, make a note of when the issue started, whether it is getting worse, which parts of the property are affected and whether alarms, smells, slow drainage, flooding, backups or pump faults are present. These details help the AFS team recommend the right next step when you call 0808 196 6005.
Quick Answer
The main signs of a blocked drain are slow-draining water, unpleasant smells, gurgling noises, water backing up, repeat blockages and outside drain overflow.
If the issue keeps returning or water is backing up, it may be more than a simple surface blockage.
1. Slow Draining Water
If water is draining slowly from a sink, bath, shower or gulley, a blockage may be building up inside the pipe.
Common causes include grease, fat, soap residue, hair, food waste and general debris.
If slow drainage keeps returning, a CCTV drain survey can help identify whether there is a deeper structural issue.
2. Unpleasant Drain Smells
Bad smells from drains often mean waste is trapped somewhere inside the pipework.
Food waste, fat, stagnant water and decomposing material can all create strong odours.
Smells should not be ignored if they are getting worse or affecting more than one drain.
3. Gurgling Sounds
Gurgling or bubbling noises usually mean air is trapped in the drainage system because water cannot pass freely.
You may hear this from sinks, toilets, baths, showers or outside drains.
Gurgling can be an early warning sign before a full blockage forms.
4. Water Backing Up
Water coming back up through sinks, toilets, showers or external drains is a serious warning sign.
This can indicate that the blockage is preventing wastewater from leaving the property correctly.
If sewage or wastewater is backing up into the property, arrange help quickly.
5. Frequent Blockages
If the same drain keeps blocking, there may be a deeper issue such as tree roots, damaged pipework, poor fall, a collapsed drain or heavy scale buildup.
Repeated blockages should not be solved with temporary fixes alone.
Read our blocked drain prevention guide for practical steps that reduce repeat problems.
6. Outside Drain Overflow
Overflowing external drains can point to a blockage in the main drainage line.
This is common after heavy rain, when leaves, silt and debris put extra pressure on older drainage systems.
External overflow can become urgent if wastewater is affecting patios, driveways, gardens or access points.
What Causes Blocked Drains?
Common causes include fat, oil and grease, wet wipes, sanitary products, food waste, hair, tree roots and collapsed pipes.
Older properties can also be more vulnerable to damaged or ageing drainage systems.
If the cause is structural, unblocking the drain may only provide a temporary fix.
What Should You Try First?
For a minor indoor blockage, you may try hot water and washing-up liquid, a plunger or a suitable drain tool.
Avoid harsh chemicals if you are not sure what pipework you have, and do not keep forcing the blockage if water is backing up.
If simple steps do not solve it, professional drain unblocking or inspection is safer.
When to Call a Professional
Call a professional if the blockage is recurring, affecting multiple drains, causing foul smells, backing up water or overflowing outside.
If damage is suspected, drain repair costs may depend on whether the problem can be patched or needs larger repair work.
Need help now? Contact Alton Facility Services for drainage support.
Next Steps
What to Check Before You Book Work
Before arranging work, check whether the issue is isolated to one appliance, one drain, one pump chamber or the wider site. Also check whether the problem happens after heavy rain, after high usage, during power cuts or only at certain times of day. These patterns can point towards different causes.
Photos of covers, chambers, alarms, control panels, visible pipework or standing water can be useful, but avoid lifting heavy covers or entering confined spaces. If sewage, foul water or electrical equipment is involved, keep people away from the area and ask for professional advice.
For non-urgent advice, use the contact form and include the property location, service required and a short description of the problem. For urgent drainage, pump or wastewater issues, call 0808 196 6005 so the team can triage the job quickly.
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