Plumbing Myths Busted: What London Homeowners Get Wrong

Myth 1: "Wet Wipes Are Flushable"

This is the most damaging plumbing myth in the UK. Despite packaging claims of "flushability" on many wet wipe brands, every water company in the country — including Thames Water — advises unequivocally that no wet wipes of any kind should be flushed down a toilet.

The problem is material composition. Toilet paper is specifically designed to disintegrate rapidly in water — within minutes of being flushed, toilet paper breaks down into fibres that pass freely through the sewer system. Wet wipes, including those marketed as "flushable", are made from synthetic fibres (polyester, polypropylene, or viscose blends) that do not disintegrate in water. They remain substantially intact, accumulate on rough spots in old cast-iron London soil pipes, and bind with kitchen fat and grease to form the notorious "fatbergs" that regularly block London's Victorian sewer infrastructure.

The scale of the problem is significant: Thames Water spends approximately £1 million per month — over £12 million per year — clearing wet wipe-based blockages from London's sewer network. The company removes over 75,000 blockages from London sewers annually, with wet wipes implicated in the large majority of non-structural blockages. The "One Square Mile" fatberg discovered under Whitechapel in 2017, weighing 130 tonnes, was predominantly composed of wet wipes and cooking fat.

The rule is simple: only the three Ps belong in a toilet — pee, poo, and paper (toilet paper only). Any deviation from this causes blockages that cost money, require plumber intervention, and contribute to a citywide infrastructure problem.

Myth 2: "Bleach Clears Blocked Drains"

Bleach (sodium hypochlorite) is a disinfectant, not a drain unblocker. It will kill bacteria in a drain, temporarily reduce unpleasant odours, and in very dilute concentrations provides some antimicrobial effect. What it will not do is physically clear a blockage of hair, soap scum, grease, wet wipes, or any physical obstruction — which is what the vast majority of blocked drains consist of.

Worse, bleach in higher concentrations can damage plastic drainage components. Modern drain pipes and waste traps are typically PVC or ABS plastic — bleach is corrosive to plastic over time, particularly at the concentrations people tend to use when "really trying to clear a drain". If you are pouring bleach down a drain that is already partially blocked and draining slowly, the bleach will sit in contact with the plastic trap and waste pipe longer than intended, increasing the corrosive effect.

If a drain is partially blocked, the correct approach is: use a drain plunger to create mechanical pressure and suction that dislodges the physical obstruction; use a purpose-made enzymatic drain cleaner (which uses enzymes to break down organic waste rather than chemicals to dissolve it); or call a plumber to rod or jet the drain. Bleach is not part of this toolkit.

Myth 3: "A Dripping Tap Wastes Very Little Water"

This seems intuitive — each drip is tiny. But the cumulative effect is substantial. A tap dripping at 20 drops per minute loses approximately 1 litre per hour. Over 24 hours, that is 24 litres. Over a year: approximately 8,760 litres — nearly 8.8 cubic metres of water.

At Thames Water's current metered water rates (approximately £1.57 per cubic metre for water plus sewerage), 8.8 cubic metres represents a cost of approximately £14–£22 per year per dripping tap — waste that provides no benefit whatsoever. For a household with two dripping taps, the annual waste cost approaches £30–£40.

Beyond the cost, a constantly dripping tap causes progressive limescale damage to the surface it drips onto — the staining and etch marks caused by mineral-laden water evaporating repeatedly on a basin, bath, or shower tray are difficult to remove once established. The drip also keeps the tap washer or ceramic disc under constant stress, which usually means the drip gradually worsens over time rather than self-resolving.

A tap washer replacement costs £50–£100 for a plumber's visit and parts. The cost is trivially small relative to a year or two of wasted water, and the repair prevents both the waste and the progressive surface damage.

Myth 4: "Boilers Need Replacing Every 10 Years"

This is a myth that, unsurprisingly, is sometimes perpetuated by sales-focused boiler installation companies. The reality: a well-maintained modern condensing boiler from a quality manufacturer — Worcester Bosch, Vaillant, Viessmann, Baxi — can reliably last fifteen to twenty years or more with annual servicing.

The critical caveat is "annual servicing". A boiler that has been regularly serviced — heat exchanger checked, flame pattern assessed, gas rate verified, ignition components inspected, condensate drain cleared, inhibitor concentration checked — will have problems identified and remediated before they become expensive failures. A boiler that has never been serviced (shockingly common in London rental properties) will experience accelerated wear from scale, sludge, and undetected early failures.

The legitimate reasons to replace a boiler before the end of its natural life are: the boiler model has been discontinued and spare parts are no longer available; repair costs exceed the replacement cost; the boiler cannot be upgraded to meet modern controls requirements (Boiler Plus, smart thermostat compatibility); or an EPC improvement is needed for rental property compliance.

Do not replace a functioning, serviced boiler simply because it is more than ten years old unless there is a specific practical or financial reason to do so.

Myth 5: "Any Plumber Can Do Gas Work"

This is not just a myth — it is a legal misconception that, if acted upon, can have serious consequences. Gas work in the UK is tightly regulated under the Gas Safety (Installation and Use) Regulations 1998. Any work on gas appliances, gas pipework, flues, or gas meters must be carried out by an engineer registered with the Gas Safe Register. This is a legal requirement, not a professional recommendation.

An unregistered person carrying out gas work is committing a criminal offence. Any gas installation they complete is technically unlawful, will not be covered by the property's insurance, and cannot be signed off with a Gas Safety Certificate. If the work subsequently causes an incident — a gas leak, a carbon monoxide escape, a fire — the legal and financial consequences for the property owner who knowingly used an unregistered operative are severe.

The Gas Safe Register is publicly searchable at gassaferegister.co.uk. Before any gas engineer touches your gas system, verify their registration and ask to see their physical Gas Safe ID card. Every registered engineer carries it. A legitimate engineer will show it proactively — there is no reason to hesitate.

Gas Safe registration replaced CORGI in April 2009. CORGI registration has not been a valid gas safety credential for over fifteen years. Any tradesperson claiming current CORGI credentials is either misrepresenting their qualifications or has not kept their credentials current.

Myth 6: "Low Water Pressure Is Thames Water's Fault"

When water pressure in a London home is lower than expected — a shower that never has sufficient pressure, taps that take a long time to fill the basin, a kettle that fills frustratingly slowly — the instinct is to blame the water company. In most cases, this instinct is wrong.

Thames Water is responsible for maintaining mains pressure in the public supply to a minimum of 10 metres head (approximately 1 bar) at the boundary of the property. Within this specification, they have met their statutory obligation. The actual pressure a household experiences depends on its internal plumbing.

The most common internal causes of low pressure that are entirely within the homeowner's control:

• Blocked tap aerator: The small mesh filter at the tip of a tap outlet collects limescale deposits over time, progressively reducing flow. Unscrewing the aerator and cleaning or replacing it restores full flow immediately. This is perhaps the most commonly overlooked cause of apparent low pressure.
• Partially closed stopcock: The main stopcock controlling the cold water supply to the property — typically under the kitchen sink — is sometimes accidentally or deliberately partially closed. A stopcock that is three-quarters open rather than fully open can reduce flow noticeably. Turn it fully open (anti-clockwise) and check whether pressure improves.
• Scaling in old pipework: London's very hard water deposits limescale on the interior walls of copper pipes over decades of use. In a Victorian or Edwardian property with original pipework that has never been cleaned, the internal bore of the pipes may be significantly reduced by scale. A professional inspection and descaling can restore flow.
• Pressure reducing valve set too low: Many London properties have a pressure reducing valve (PRV) on the incoming supply to prevent damage from high-pressure mains surges. If the PRV has been set at an unnecessarily low pressure — a common oversight after any work on the supply — adjusting it upward (within safe limits for the property's fittings) can improve flow throughout the property.

Before concluding that Thames Water is at fault for low pressure, check all of the above. If all internal causes have been ruled out and confirmed neighbours also have low pressure, then contact Thames Water on 0800 009 3 002 to report a supply pressure issue.