Slow or blocked waste is usually a trap, a badly fallen branch pipe or a build-up further down the run. Smells almost always mean a trap has lost its water seal – either dried out or siphoned. Both are fixable, but only if somebody establishes which is happening rather than pouring chemicals down it.
What a trap actually does
Every waste fitting in the house has a trap – the U-bend under a sink, the bottle trap under a basin, the integral trap in a toilet pan, the shallow trap under a shower. Its only job is to hold a small plug of water that stops sewer gases coming back up the pipe into the room. It is a beautifully simple device and almost every drainage smell in a house is a trap that has lost its water.
A trap loses its seal in two ways. It dries out, which happens in a guest bathroom or a utility sink nobody uses – the fix is running the tap for thirty seconds. Or it is siphoned, which happens when a large discharge somewhere else on the same branch pulls the water out of it. Siphonage is a design problem: it means the pipework is not venting properly, and it will keep happening.
If one fitting gurgles when a different one drains, the system is pulling air through the trap seal because it cannot get air anywhere else. That is a venting fault. Clearing the blockage will not stop it, and the smell will return.
Why a particular sink keeps blocking
Repeat blockages in the same place are almost never about what is being put down it. They are about the pipe.
- Insufficient fall. Waste pipe needs a consistent gradient. Too shallow and solids settle; too steep and the water outruns the solids, leaving them behind. Both produce a pipe that silts up.
- A sag in a long run. Unsupported plastic waste pipe droops over time, creating a low point that holds standing water and collects everything that passes.
- Too many bends. Every 90-degree elbow is a place for material to catch. Two swept bends will outlast one tight one indefinitely.
- A reduction in diameter, usually where somebody has connected a 32mm run into an existing 40mm system the wrong way round.
- A shared branch with an appliance. Washing machine and dishwasher discharges carry detergent, grease and fibre, and they discharge fast. A sink teed into that branch downstream of the appliance collects the residue.
- Grease, on a kitchen run. Fat goes down warm and liquid, then solidifies on the pipe wall in the cold section. It builds in layers and it does not clear itself.
We would rather establish which of these you have and fix it than come back every eighteen months with a set of rods.
Chemical drain cleaners
A word about these, because they are the first thing most people reach for. Caustic drain cleaners will dissolve organic matter, and on a genuine hair or soap blockage in a basin they often work. They have three problems worth knowing about.
- They do nothing to a blockage that is not organic – a build-up of silt, a dropped object, a structural fault, or hardened grease is unaffected.
- If they do not clear it, you now have a pipe full of caustic solution that the next person has to open up. Tell whoever comes out what you have used.
- Repeated use damages older pipework, particularly the rubber seals in compression waste fittings and any remaining cast iron.
Boiling water and a plunger, used properly, clears more than people expect. Beyond that, a trap comes off and gets cleaned – which takes ten minutes and tells you what the blockage was actually made of, which is information a chemical never gives you.
Leaks under the sink
The area under a kitchen sink is where the greatest number of individual connections in the house are concentrated, and it is the place people look least often. The things that fail, roughly in order:
| Component | Failure mode |
|---|---|
| Braided flexible tap tails | The inner hose perishes and the braid lets go. This is the single most common cause of serious kitchen water damage |
| Compression waste joints | Seals harden, or the joint was cross-threaded at installation and has weeped slowly ever since |
| Sink-to-worktop seal | Silicone fails and water runs around the rim of the bowl, soaking the chipboard from above rather than below |
| Waste disposal connections | Vibration loosens joints over time |
| Appliance hose connections | Often the last thing anyone checks, and often the source |
A swollen, dark chipboard cabinet base is telling you there has been a slow leak for a long time. Finding which of the above it is takes drying everything, running each item in turn and watching – which is not glamorous, but it is the only reliable method.
Draining slowly or smelling? The cause is usually identifiable in one visit.
Questions we get asked about this
Why does my sink smell even though it drains fine?
Almost certainly a trap with no water in it, or a trap being siphoned dry by another appliance on the same branch. Run the tap for thirty seconds and see if the smell goes. If it returns within a few days, it is siphonage and the pipework needs looking at.
Is a blocked drain my responsibility or the water company’s?
Inside your property boundary, pipework serving only your home is yours. Shared drains and the sewer beyond the boundary are generally the water company’s. If a blockage is affecting more than one property, call them – it may cost you nothing.
Can you clear a blockage the same day?
Usually, for internal waste. A completely blocked kitchen or bathroom is treated as urgent because it makes the house hard to live in.
Will you tell me why it blocked?
Yes, and where the cause is structural rather than incidental we will tell you that too, even though it means a bigger conversation. Clearing the same blockage repeatedly is not a service.
Do I need the waste pipe replacing?
Only if the pipe itself is the problem – wrong fall, a sag, too many tight bends, or a reduction. Where it is simply dirty, cleaning it properly is the answer. We will tell you which.
What about outside drains and gullies?
We deal with the run up to and including the gully. Blocked shared drains, collapsed clay pipework and anything needing a camera survey beyond that point is a drainage specialist’s job and we will say so rather than guessing at it.
What happens when you call
Call and describe it
You speak to an engineer, not a call centre. Most jobs can be narrowed down on the phone.
We look at it properly
A real diagnosis before a price, and a straight answer if it is not worth doing.
A written quote
Itemised, so you can see what you are paying for.
The job, and the paperwork
Certificates where the work needs them, and what will need attention next.
Where we do this work
Across Norwich and the whole of Norfolk. If you are on the edge of the county, call and ask — we will tell you honestly whether we are the right people.
- Norwich
- Wymondham
- Dereham
- Attleborough
- Aylsham
- North Walsham
- Cromer
- Diss
- Loddon
- Long Stratton
- Watton
- King's Lynn
Need this doing?
Call and describe the problem — you will speak to an engineer, not a call centre. Written quotes, no estimates over the phone.