Plumbing Survey: What It Checks and When You Need One

Why a homebuyer survey is not enough

A building survey looks at the whole property, and the surveyor is not a plumber. The report usually notes the type of heating and hot water, comments on anything visibly wrong, and then recommends that the services are checked by a specialist before you commit. That recommendation is easy to skim past, but it is there because nobody has run the taps, looked at the pressure, checked the cylinder safety valves or tested for a hidden leak.

In London that gap matters more than most places. Much of the housing stock is old, many houses have been split into flats with plumbing rerouted several times, and it is still common to find a lead supply pipe, a cylinder that is decades old, or a stopcock that has not turned in years.

What a plumbing survey should check

On a property with an unvented cylinder, the paperwork deserves as much attention as the hardware. An unvented cylinder should have been installed by someone qualified under Part G3 of the Building Regulations, notified to building control, and left with a commissioning record and a service history. If none of that exists, it does not mean the cylinder is unsafe, but it is a question for the seller and a reason to have it serviced soon after you move in. Our guide on how to check a plumber is qualified for unvented work explains what the paperwork should show.

• The stopcock: where it is, whether it turns, and whether it actually shuts the water off
• The supply pipe: what it is made of where it enters the property, including whether it is lead
• Mains pressure and flow: a timed flow test at the kitchen tap and a pressure reading, which decide what hot water system the property can support
• Hot water: the type of system, the age and condition of the cylinder or water heater, the immersion heater, and signs of leaks or corrosion
• Unvented cylinder safety: the pressure and temperature relief valves, the tundish and discharge pipe, the expansion vessel, and the paperwork
• Hidden leaks: a meter test with every tap closed, plus a look for staining, damp and dripping joints under sinks and in cupboards
• Pipework: materials, any mixed or poorly joined sections, lagging in the loft, and isolation valves on appliances
• Cold water storage: the condition of any loft tank, its lid, insulation and overflow
• Taps, toilets, showers and the washing machine and dishwasher connections

What a plumbing survey cannot tell you

A plumber can only assess what can be seen, reached and safely tested. Pipes buried in floors and walls, under concrete slabs and behind fitted kitchens are judged from the outside, from the meter test and from any signs of damp. If there is evidence of a hidden leak, finding it precisely is a separate job with its own equipment, which our leak detection and repair service covers.

Gas appliances are a separate matter too. A boiler, gas fire or gas hob should be checked by a Gas Safe registered engineer, and you can confirm anyone offering to do that on the register in about a minute; our guide on how to check a plumber on the Gas Safe Register shows how. Underground drains are also outside a plumbing survey, and need a drain survey with a camera if there is any sign of trouble.

In a flat, some of the plumbing may belong to the building rather than to you. The rising main, shared tanks and pipework in communal areas are usually the freeholder's responsibility, and a survey can only point out what is visible from inside your property. Our guide on who is responsible for a leak in a leasehold flat covers where that line usually falls.

When a plumbing survey is worth having

Landlords have legal duties around hot water and safety that make a check before each tenancy sensible. Our guide to landlord hot water responsibilities sets those out.

• Buying an older house or a converted flat, especially one that has been empty for a while
• Buying a property with an unvented cylinder and no paperwork
• Before letting a property, so you know the hot water and the stopcock work before a tenant needs them
• After a tenancy ends, when you want to know what needs repairing before the next one
• Planning a new bathroom or kitchen, so you know whether the supply and hot water can cope first
• When the water bill has jumped and you suspect a leak somewhere

Getting the most from the visit

Book the survey for a time when the water is on and the property is accessible, including the loft, the airing cupboard, the kitchen cupboards and the meter. If the property is vacant, ask the agent to make sure the utilities are connected, because a survey with the water off can tell you very little.

Tell the plumber what you are planning. If you want to add a second bathroom, switch to an unvented cylinder or move the kitchen, the flow test and the supply pipe matter much more than if you plan to leave things as they are.

Ask for the findings in writing, with the urgent items separated from the ones that can wait. If you are buying, that list is useful when you talk to the seller about the price. If something needs immediate attention, such as a leaking relief valve or a stopcock that will not close, get it quoted separately so you know what you are dealing with.

A plumbing survey is an assessment of condition on the day. It is not a guarantee that nothing will fail later, and nobody honest will describe it as one.

What decides the cost

The time a survey takes depends on the size of the property, how many bathrooms and appliances there are, whether there is a cylinder to inspect, and how easy it is to reach everything. A one bedroom flat with a combi boiler is a much shorter visit than a large house with an unvented cylinder, a loft tank and three bathrooms.

We charge surveys at our normal hourly rate, with the call-out, both of which are on the pricing page and agreed before we attend. The rate does not change on the day, and the total depends on how long the property takes to go through.

Book a plumbing survey

If you are buying, letting or taking over a property and want to know the state of the plumbing and hot water, call 020 4652 5111. Tell us the type of property, what hot water system it has if you know, and anything the homebuyer report flagged. We have 20 engineers across London, so a visit before exchange is usually straightforward to arrange.