First-Time Buyer Plumbing Guide — What to Check Before Buying a London Property
London property surveys often miss plumbing defects that cost thousands to fix. This guide tells first-time buyers what to look for, what questions to ask, and what a plumbing survey covers that a standard RICS valuation does not.
Why Standard Surveys Often Miss Plumbing Problems
A standard RICS Level 2 Homebuyer Report — the most commonly purchased survey for London properties — is a non-invasive visual inspection. The surveyor cannot lift floorboards, access voids, or pressure-test pipework. Most plumbing defects are hidden and will not be visible from a surface inspection.
A specialist plumbing survey (commissioned separately, costs £150-350) is strongly advisable for any London property built before 1970, any property with a gravity-fed system, or any property where the boiler is more than 8 years old.
What to Check During Viewing
Boiler Age and Type
- Ask the agent for the boiler make and model — you can look up installation dates from the serial number via the manufacturer's website
- Boilers over 10 years old are beyond their typical warranty life and may need replacement (£2,000-3,000) — factor this into negotiation
- Old back boilers (boilers fitted behind a gas fire, common in 1970s-1980s London properties) are inefficient and parts are scarce — replacement is expensive and involves wall opening
Water Pressure
Run a cold tap and observe pressure. In London, mains cold pressure should give a good flow. If cold taps have weak flow, either there is a partially closed stopcock or the mains supply is inadequate — which is the water authority's responsibility but can take months to resolve.
Hot Water System Type
- Combi boiler: Modern, no tanks, pressurised hot water. No storage delay but performance affected by scale in London hard water areas.
- Gravity-fed (vented) system: Identify by the cold water tank in the loft. Hot water pressure will be low on upper floors without a pump.
- Unvented cylinder: Identify by a large cylinder (often in an airing cupboard) with a pressure relief valve. Mains pressure hot water. Requires G3 servicing.
Lead Pipework
Properties in inner London built before 1970 may have lead supply pipes — from the water main in the street to the property. Lead leeches into drinking water and presents a health risk. The water authority (Thames Water) will replace their section of lead main under a lead pipe replacement scheme, but you are responsible for the supply within the boundary.
Lead pipes are identifiable by colour (dull grey), softness (you can dent them with a thumbnail), and their tendency to form "swelling" at soldered joints. Replacement of internal lead pipes: £800-2,500 depending on property size.
Drainage
Request a CCTV drain survey (£150-300) on any London property over 40 years old. Victorian clay drains crack, root-ingress is ubiquitous, and bellied (sagging) drain sections are common under Victorian London gardens. A blocked or collapsed drain after purchase can cost £2,000-8,000 to repair.
Frequently asked questions
Should I get a specialist plumbing survey when buying a London property?
Yes, for any pre-1970 property, any property with a gravity-fed system, or any property where the boiler is over 8 years old. A specialist plumbing survey costs £150-350 and can identify issues that cost thousands to fix post-purchase. For a property costing £400,000+, this is proportionally trivial insurance.
What is a CCTV drain survey and do I need one?
A CCTV drain survey sends a camera into the drain system to check for cracks, root ingress, bellied sections, and blockages. It costs £150-300 and is strongly advisable for any London property with Victorian drains (pre-1940). Many drain problems are only visible with a camera — and a collapsed drain after purchase can cost £5,000+.
How can I tell if a London property has lead pipes?
Look under the kitchen sink at the pipe coming up from the floor to the stopcock. Lead pipes are dull grey (not bright silver like copper, not white/grey plastic), soft enough to dent with a fingernail, and often form a slight bulge at soldered joints. If in doubt, a plumber can identify them during a viewing or survey visit.
What should I ask the agent about plumbing before making an offer?
Ask: how old is the boiler and when was it last serviced? Is there a gas safety certificate (required for flats/managed properties)? Has there been any water damage or leak history? Are there any drainage issues? Is there a loft cold water tank? Has any recent plumbing work been done and are the building regulations completion certificates available?