Every drainage question, answered properly

The strongest drain unblocker is not a chemical — it is high-pressure water jetting, which cuts through fat, scale, roots and debris at up to 4,000 psi without damaging the pipe. Of shop-bought products, sodium hydroxide (caustic) gels are the strongest, but they are dangerous and do not clear structural blockages.

The 135 rule refers to the 135-degree bend: drainage direction changes should be made with 135° bends (or two 45s) rather than sharp 90° elbows, because a gentler sweep keeps flow velocity up, lets rods and jetting hoses pass, and greatly reduces the chance of blockages forming at the bend.

A drain that keeps blocking in the same place almost always has an underlying structural cause — a cracked pipe, an open or displaced joint, root ingress, a bellied section holding water, or a badly formed bend. Debris catches on the defect, so clearing it only buys time.

Start by finding where the blockage is: run each fixture in turn. If one is slow, clean its trap. If everything on the ground floor is slow, the blockage is in the underground drain and DIY tools will not reach it. Never keep flushing a blocked toilet.

Hot water can soften a light grease film in a kitchen waste pipe, but it rarely clears a real blockage — the fat simply re-solidifies further along the pipe. Never pour boiling water into a ceramic WC pan or through plastic waste pipes, as it can crack the pan and distort fittings.

Baking soda and vinegar produce a fizzing reaction that can loosen light residue and reduce odours in a slow-running plughole. It has no useful effect on a compacted blockage, a fat deposit, wet wipes or anything in an underground drain — the reaction is over in seconds.

Never put fats, oils or grease, wet wipes (including "flushable" ones), nappies, sanitary products, cotton buds, coffee grounds, rice or pasta, paint, cement, or caustic chemicals down a drain. These are the direct cause of the overwhelming majority of blockages we attend.

Professionals locate the blockage first — lifting chambers to see which runs are full — then clear it with drain rods for close, soft blockages or high-pressure water jetting for anything compacted, greasy or rooted. A camera check afterwards confirms the pipe is clear and shows why it blocked.

High-pressure jetting clears drains by firing water through a specialist nozzle at up to 4,000 psi. Rear-facing jets propel the hose along the pipe while scouring the wall clean, removing fat, silt, scale and roots and restoring the pipe to its full bore rather than punching a hole through the blockage.

Correctly performed jetting does not damage sound pipework. Damage occurs when excessive pressure is used on already-compromised pipes — old pitch fibre, cracked clay or badly corroded cast iron. A competent engineer assesses the pipe material and condition first and adjusts pressure and nozzle accordingly.

Most domestic drain blockages are cleared within 30 to 60 minutes of the engineer arriving. Simple internal blockages can take 15 minutes; heavily compacted fat, root masses or blockages in long shared runs can take two to three hours including a camera check afterwards.

A fatberg is a solid mass formed in a drain or sewer when congealed fats, oils and grease bind together with wet wipes, sanitary items and other non-flushable debris. Fatbergs harden into a concrete-like mass that blocks flow and must be cut out with high-pressure jetting.

Caustic and acid-based drain unblockers can corrode old lead, copper and cast iron pipework, soften some plastics and damage seals. They also generate heat, which can distort plastic traps. In underground drains they are diluted to uselessness and simply pollute.

A domestic pressure washer with a drain-cleaning lance attachment can clear light silt in a short gully run, but it lacks the pressure and flow to shift compacted fat, scale or roots, and used carelessly it can force water back into the property or damage old pipework.

New build drains most often block because of construction debris left in the system — cement, plaster, brick fragments and site rubbish — or because of poor gradients and badly formed connections. Both are defects, and on a new home they should be raised with the developer under warranty.

Drain rods work well on soft blockages within reach of an access point — typically the first 10 to 15 metres from a chamber. They are ineffective against compacted fat, scale and roots, and can make things worse if the head unscrews and is lost in the pipe.

The most common causes, in order, are fats, oils and grease in kitchen runs, wet wipes and sanitary items in foul runs, hair and soap scum in bathroom wastes, leaves and silt in external gullies, and root ingress through failed joints in older clay pipework.

Sometimes, using a rodding eye or working back from a gully, but lifting the chamber is almost always the right first step. It shows which section is blocked in seconds and prevents the engineer working blind and clearing the wrong run.

Yes. Most damaged drains are repaired without excavation using no-dig lining: a resin-impregnated liner is inserted into the damaged pipe, inflated and cured in place, forming a watertight new pipe inside the old one. It seals cracks, open joints and root entry points without lifting a single slab.

A damaged drain is repaired by first running a CCTV survey to locate and grade the defect, then choosing the least invasive fix: patch lining for a localised crack or open joint, full-length relining for a degraded run, and excavation and re-lay only when the pipe has collapsed beyond lining.

The classic signs of a broken underground drain are blockages that keep returning after clearing, damp patches or sinkage in the ground above the pipe run, unusually lush grass over the drain line, rat activity, and slow drainage after heavy rain. A CCTV survey confirms it.

Under Building Regulations Part H, foul drains in private ground should normally be laid at least 600mm below any surface subject to vehicle loading and at least 300mm under areas with no traffic. Depths below 300mm need protective concrete surround or slabbing.

Most drain repairs are completed in a single visit. A patch liner takes two to four hours including curing, a full-length reline of one run takes half a day, and an excavation and re-lay of a short section usually takes one to two days depending on depth and access.

A correctly installed CIPP drain liner has a design life of 50 years or more. The cured resin liner is a structural pipe in its own right, is chemically resistant, has a smoother bore than the original clay, and permanently seals the joints roots were entering through.

A patch liner is a short resin-impregnated sleeve — usually 0.5m to 1.5m long — installed inside a drain to seal a single localised defect such as a crack, open joint or root entry point. It is positioned on an inflatable packer, cured in place, and needs no excavation.

Yes. Roots are cut out with a rotating high-pressure jetting head or a mechanical root cutter, which strips the root mass back to the pipe wall. Cutting alone is temporary though — the roots regrow within months unless the joint they entered through is sealed with a liner.

Drains collapse from age-related failure of Victorian clay pipework, ground movement, root pressure at joints, vehicle loading over shallow pipes, and poorly built extensions that load or disturb an existing run. Repeated blockages and jetting of an already-cracked pipe can finish it off.

Repairs and like-for-like replacement of existing drains do not need building control approval. Building a new drain, altering an existing run, connecting to a public sewer or building over or near a drain does require approval under Building Regulations Part H.

Descaling removes hard mineral scale, rust and concrete residue from the inside of a pipe, usually with a rotating chain-flail head or a milling cutter on a jetting hose. It restores the full bore of cast iron and old clay pipework that jetting alone cannot clean.

A bellied drain is a section of pipe that has sagged below the correct gradient, creating a dip that holds standing water. Solids settle in the dip instead of being carried away, so the run silts up and blocks repeatedly until the gradient is corrected.

A 100mm foul drain should typically fall at 1 in 40 to 1 in 80, and a 150mm drain at around 1 in 150, subject to the flow it carries. Too shallow and solids settle; too steep and water outruns the solids, leaving them behind.

Pitch fibre pipe is a lightweight bitumen-impregnated wood-fibre pipe used in UK housing from the 1950s to the 1970s. It deforms into an oval shape over time, blisters internally and delaminates. Most pitch fibre drainage is now at or beyond the end of its life.

Signs of a leaking drain include persistent damp at low level on walls, an unexplained soft or sunken patch of ground, a sewage smell outdoors, unusually lush vegetation along the pipe line, and rat activity. A CCTV survey with a water or dye test confirms it.

Yes. A leaking drain washes fine material out of the soil beneath and beside foundations, creating voids that lead to settlement. Escape of water from defective drains is one of the recognised causes of domestic subsidence in insurance claims.

Drain relining installs a new pipe inside an existing damaged one without excavation. A resin-soaked liner is inserted through a chamber, inflated against the pipe wall and cured, forming a seamless, jointless pipe with a 50-year design life and a smoother bore than the original.

Yes — this is exactly where no-dig lining is most valuable. A liner is installed from an accessible chamber outside the building and cured in place under the floor, repairing the run without lifting floors, breaking through slabs or excavating inside the property.

Modern PVC drainage has a design life of around 100 years, and vitrified clay a similar span. In practice, failure comes from the joints and the ground rather than the pipe: Victorian clay systems commonly start failing at 80-120 years, and pitch fibre at 40-50.

A CCTV drain survey pushes a self-levelling HD camera through the drainage system on a rod or crawler, recording the condition of every accessible run. The engineer logs each defect against the WRc grading standard and produces a video, a defect report and a recommended repair plan.

Yes, if the property is over 50 years old, has mature trees within 10 metres of the drain run, has been extended, or your survey flags anything drainage related. Standard homebuyer and building surveys do not inspect underground drainage at all — it is outside their scope.

A standard domestic CCTV drain survey takes 60 to 90 minutes on site. Larger properties, commercial premises or systems with many chambers take two to four hours. The written report and footage are normally issued within 24 hours of the visit.

A drain survey report shows a plan of the drainage layout, the direction of flow, the material and diameter of each run, every defect logged with its distance from the access point, a WRc severity grade for each, and a recommended repair method with indicative costs.

Not usefully. The blockage has to be cleared first, because the camera cannot pass it and standing water hides the pipe wall. Engineers normally jet the run, then survey immediately afterwards — clearing and surveying in the same visit is the efficient way to do it.

WRc grading is the Water Research Centre standard used to classify drainage defects from Grade 1 to Grade 5. Grade 1 is cosmetic with no action needed; Grade 3 is a significant defect to plan for; Grade 4 and 5 are structural failures that need repair now.

Hidden chambers are located by tracing the drain run with a camera fitted with a sonde and following the signal from the surface with a locator wand, or by checking the water company's sewer records and the property's drainage plan. Both methods avoid random digging.

A dye test introduces coloured non-toxic dye into a fixture or drain and tracks where it emerges. It is used to prove which drain a fixture connects to, identify misconnections between foul and surface water systems, and confirm the source of a leak or pollution.

Request the sewer records from your water and sewerage company for public pipes, check the property's building control drawings for private runs, and for anything unrecorded use a CCTV survey with sonde tracing to map the layout accurately from chamber to chamber.

Yes. A flexible push-rod camera can be fed through a WC pan into the soil pipe where no external access exists, though surveying from a manhole or rodding eye gives better results. The camera is disinfected between jobs and does not damage the pan.

Lift an inspection chamber and look at the pipe: clay is buff or reddish-brown with visible joints, plastic is orange-brown or grey and smooth with sealed sockets. As a rule, properties built before about 1970 have clay drainage and those after have PVC.

Survey domestic drainage every five to ten years, and sooner if you have recurring blockages, mature trees near the run, clay pipework, or plan to extend or pave over a drain. Commercial premises with heavy loading should survey annually alongside planned jetting.

You are responsible for the drains inside your property boundary that serve only your home. Shared drains and everything beyond the boundary are the water and sewerage company's responsibility, and they will clear those free of charge. Lateral drains outside the boundary transferred to water companies in 2011.

A drain shared by two or more properties is the responsibility of the water and sewerage company following the 2011 private sewer transfer, and they will clear a blockage free of charge. You only pay if the blockage is in the section of pipe serving your property alone.

Yes. Under Section 11 of the Landlord and Tenant Act 1985, landlords must keep drains and sanitary fittings in repair and proper working order. The exception is a blockage caused by tenant misuse — flushing wipes or pouring fat away — where costs can be recharged.

Standard buildings insurance usually covers accidental damage to underground pipes and sometimes collapse, but not blockages, wear and tear, or gradual deterioration. Many policies include an optional home emergency add-on that does cover drain clearance — check your schedule before paying.

Road gullies and highway drainage are the local highway authority's responsibility — the county council in most areas. Blocked public sewers are the water and sewerage company's. Neither is a cost to you, so report it rather than paying a private contractor.

A lateral drain is the section of pipe carrying waste from your property boundary to the public sewer. Since October 2011 lateral drains in England and Wales have been the responsibility of the regional water and sewerage company, not the homeowner.

A drain serves a single property. A sewer serves more than one property. That distinction determines who pays: drains within your boundary are your responsibility, while sewers and lateral drains are maintained by the regional water and sewerage company.

Call your regional water and sewerage company's 24-hour emergency line — Thames Water, Southern Water or the relevant provider for your postcode. Blocked public sewers and lateral drains are their responsibility and they attend at no cost to you.

DrainFixer operates 24 hours a day, seven days a week, and aims to be with you within about 60 minutes for emergencies across London and a 25-mile radius of East Grinstead. Non-urgent work such as surveys and planned repairs is normally booked within a day or two.

Yes. DrainFixer runs a genuine 24/7 rota — nights, weekends and bank holidays included. Drainage emergencies do not keep office hours: sewage backing up at 2am needs the same response as it would at 2pm, and the same engineers and equipment attend.

The engineer identifies the affected run by lifting chambers and checking which are full, clears the blockage with rods or high-pressure jetting, runs a camera through to confirm the pipe is clear, explains what caused it, and gives you a written note of anything that needs following up.

Choose a company that diagnoses before it quotes, carries jetting and CCTV on every van, gives the price in writing before starting, hands over camera footage, and recommends lining before excavation. Be wary of anyone quoting excavation without showing you a survey first.

A properly equipped drainage van carries drain rods and a range of heads, a high-pressure water jetter with penetrating, flushing, rotating and root-cutting nozzles, an HD CCTV push-rod camera with sonde location, manhole keys, a wet vacuum, and patch lining kit for on-the-spot repairs.

For external drainage work you usually need to provide access to the property and any locked gates, but you do not have to be present throughout. For internal work, or where chambers are inside the building, someone over 18 needs to be there for the duration.

Commercial drains should be jetted and inspected at least annually, and quarterly to monthly where food is prepared. Restaurants, takeaways, pubs and care homes generate heavy fat and solids loading, and a scheduled programme is far cheaper than closing for an emergency.

A grease trap separates fats, oils and grease from kitchen waste water before it enters the drain. Any commercial kitchen preparing hot food needs one — water companies and environmental health can enforce installation, and without one FOG blockages are effectively guaranteed.

Yes. A buyer's drainage survey that finds defects becomes a price negotiation or a delay at the worst possible moment. Surveying and repairing beforehand costs less than the reduction a buyer will ask for, and a clean report is a genuine selling asset.

Never pour fat or oil down the sink, bin all wipes, fit strainers and hair catchers, run water into unused fixtures monthly, clean traps quarterly, clear external gullies twice a year, and have a CCTV survey done every five to ten years or after any recurring blockage.

Ask: will you confirm the price in writing before starting, will you camera-check the run afterwards, will I get a copy of the footage, are you insured, and if you recommend excavation can you show me the survey that justifies it rather than lining.

It matters a great deal. Any drainage contractor working at your property should carry public liability insurance covering damage to your property and third parties. Ask for confirmation before work starts, particularly for jetting, lining and any excavation.

Do not flush again — that is how bathrooms flood. Turn off the isolation valve behind the pan, let the level drop, then use a proper toilet plunger with a flange, or a closet auger. If two or more fixtures are also backing up, the blockage is in the drain outside, not the pan.

A gurgling toilet means air is being pulled through the trap because the drain or soil vent is partially blocked. Water displaced by a blockage downstream forces air back up the nearest trap. It is an early warning that a full blockage is forming — get the run checked before it stops completely.

A toilet that fills high then drains away slowly has a partial blockage — usually in the pan trap, the soil pipe, or the underground drain. Solids are passing but the bore is restricted. If other fixtures are also slow, the restriction is in the shared drain outside the property.

No. Wipes marketed as flushable pass the toilet but do not disintegrate in water the way toilet paper does. They snag inside the pipe, bind with fats and grease and form fatbergs. Water companies and drainage engineers agree: bin them, never flush them.

A toilet that blocks repeatedly usually has a cause beyond what is being flushed: a partially blocked soil pipe, a damaged or scratched pan trap, insufficient flush volume, or a defect in the underground drain. A camera survey through the run identifies which.

Stop using every water outlet in the property immediately, keep children and pets out of the affected area, ventilate the room, do not touch the waste with bare hands, and call a drainage engineer straight away. Every flush and every sink of water adds to the spill.

Kitchen sinks block because fats, oils and food residue cool and set on the inside of the waste pipe, gradually narrowing it until nothing passes. The blockage is usually in the trap under the sink or in the first few metres of horizontal waste pipe behind it.

A slow shower is almost always a hair and soap-scum plug in the trap or the first section of waste pipe. Lift the grille, remove the visible mass with pliers, then use a wire hook or Zip-It tool to pull out the deeper build-up. Flush through with hot water and detergent.

The washing machine discharges a large volume of water very quickly. If the shared kitchen waste run is partially blocked with fat and detergent scum, that surge has nowhere to go and pushes back up the nearest opening — normally the sink, because it is the lowest.

A bath that will not drain has a hair and soap plug in the trap or the overflow branch. Remove the plug grille, hook out the hair mass, then clean the trap. If the bath is on the ground floor and the kitchen sink is also slow, the shared underground run is the problem.

Clean a kitchen sink trap every three months and a bathroom basin or bath trap every six months. In a busy household or one where cooking oils are used heavily, monthly is better. It takes ten minutes and prevents the majority of household blockages.

A gurgling sink means air is being drawn through the trap because the waste pipe or vent is partially restricted. It is an early warning of a developing blockage — the pipe is still passing water, but not freely, and air is being pulled past the trap seal.

Lift the gully grid, put on gloves and scoop out leaves, silt and debris by hand, then flush with a hose. If the water level does not drop, the blockage is further down the run and needs drain rods or jetting from the nearest chamber — do not force a hose down a manhole.

An overflowing manhole means the drain run downstream of that chamber is blocked. Waste water arrives faster than it can leave, so the chamber fills and spills. Stop using water in the property immediately and call a drainage engineer — every flush adds to the overflow.

Drains overflow in heavy rain when the surface water system is blocked with leaves and silt, when the pipe is undersized or partially collapsed, or where surface water is wrongly connected into the foul drain so both systems surge together.

Clean external gullies at least twice a year — once in late autumn after the leaves have fallen and once in spring. Properties under mature trees or with block paving that sheds grit need quarterly cleaning to prevent silt build-up and surface flooding.

A foul drain carries waste water from toilets, sinks, baths and appliances to the sewer for treatment. A surface water drain carries rainwater from roofs and paving to a soakaway, watercourse or separate sewer. In most modern properties the two systems are entirely separate.

A soakaway is a buried void — traditionally rubble, now usually plastic crates — that lets rainwater disperse into the surrounding ground. It has failed when water pools above it, gullies back up in rain, or the ground stays saturated for days after rainfall stops.

You can build over a private drain that serves only your property, but building over or within 3m of a public sewer requires a build-over agreement from your water and sewerage company. Approval normally requires a CCTV survey and protective measures such as a lintel over the pipe.

A rodding eye is a capped access point at ground level giving direct entry into a drain run for rods, jetting hoses and survey cameras. It is fitted where a full inspection chamber is not practical, typically at the head of a run or at a change of direction.

Underground drains rarely freeze because they sit below frost depth, but exposed external waste pipes, condensate pipes and shallow runs can. Lag exposed pipework, keep gullies clear so water does not stand, and never pour fat away in cold weather — it sets instantly.

A non-return valve allows waste water to flow out of a property but prevents it flowing back in. It is fitted in a chamber on the outgoing run and protects basements, lower ground floors and properties on shared or overloaded sewers from sewage backflow flooding.

Inspection chambers are usually near the rear of the property in line with the soil pipe, at changes of direction, and close to the boundary where the drain leaves the plot. Look for square or round metal or plastic covers in paths, drives, patios and lawns.

A chamber should be empty apart from a shallow flow in the benched channel. Standing water means the run downstream is restricted or blocked. If the level is at or near the top, the blockage is significant and the property is at risk of backing up.

Drain smells are caused by a dry or lost trap seal, a build-up of decaying matter in the waste pipe, a blocked soil vent pipe, or a cracked drain releasing sewer gas into the ground beside the property. Running water into unused fixtures fixes the most common cause in seconds.

A sewage smell in a garden usually means a cracked or leaking drain, an open or displaced joint, or an overflowing chamber. Sewer gas and effluent escaping into the soil produces a persistent smell that gets worse in warm, still weather.

Yes, though it is rare. Rats are strong swimmers and can travel through sewers and up a soil pipe into a WC if there is a defect in the drainage — typically a broken pipe, a redundant open connection or a missing rodding cap. A one-way drain valve prevents it.

Seal the route. Survey the drainage to find broken pipes, open joints and redundant connections, repair them with lining or replacement, cap any disused pipework, and fit a one-way rat blocker valve in a chamber if the property backs onto a sewer with known activity.

Warm weather accelerates the bacterial breakdown of waste in pipes and chambers, producing more hydrogen sulphide gas, and it evaporates trap seals in unused fixtures faster. Both effects mean an existing minor drainage fault becomes noticeable in summer.

Heavy rain surcharges the sewer, pushing air and gas back through the system. Where a trap seal is weak, a vent is blocked or a pipe is cracked, that displaced gas escapes into the property or garden — which is why the smell appears with the weather.

Sewage backing up inside a property, an overflowing manhole, a completely blocked toilet in a home with only one WC, flooding that threatens a building, and any drainage failure stopping a business from trading all count as emergencies and warrant an immediate call-out.

Stop using every water outlet in the property — no toilets, taps, showers, washing machine or dishwasher. Keep people and pets away from any sewage, open windows to ventilate, move valuables off the floor of affected rooms, and photograph the damage for insurance.

Yes. Sewage carries bacteria, viruses and parasites including E. coli, hepatitis A and gastroenteritis pathogens, and produces hydrogen sulphide gas. Keep children and pets away, do not touch it with bare skin, ventilate the area, and have the affected surfaces professionally disinfected after clearance.

That means the blockage is inside your boundary in a pipe serving only your property, so you need a private drainage contractor. Ask the water company where exactly they determined the blockage sits — that information tells your engineer where to start and saves time on site.

Yes. A leaking or blocked underground drain saturates the ground next to the foundations, and that moisture is drawn into the wall structure, producing persistent damp at low level that no amount of internal treatment will cure until the drain is repaired.

Water rising in a ground-floor shower tray means the drain serving the property is blocked and the tray is now the lowest available overflow point. Stop using water in the building immediately and call a drainage engineer — the level will rise with every flush.

Yes. Once the drain is blocked, waste water backs up to the lowest opening in the system, which in many houses is a ground-floor shower, bath or WC. If water keeps being used, the property floods with contaminated water within a short time.

Have the drain cleared first, then remove and dispose of contaminated porous materials such as carpet, underlay and chipboard, wash hard surfaces with detergent followed by a disinfectant, ventilate thoroughly and dry the area completely. Photograph everything before you start for insurance.

Yes. Jetting units are used year-round; equipment is protected against freezing and the work continues in cold weather. Winter is one of the busiest periods for drainage because kitchen fats set instantly on cold pipework and blockages form faster.