Water Testing Before Buying a House: 5 Checks Your Survey Won't Do
Updated: 2 days ago
Last reviewed: September 2026
Quick answer A standard survey looks at the building, not the water. Before you exchange, check five things: (1) mains or private supply, (2) lead pipes, (3) loft tanks and which taps are mains-fed, (4) hardness, and (5) for a private supply, the paperwork and recent test results. Most of this takes a few questions and a look under the kitchen sink. Water testing before buying a house fills the gaps.
Buying a pre-1970 home? A first-draw Lead Test is a quick way to screen whether lead pipes are affecting the water.
Check 1: Is the house on mains water or a private supply?
Your conveyancer's drainage and water search (often called a CON29DW in England and Wales) shows whether the property is connected to the public water supply and sewer. Don't rely on the listing — rural and older properties sometimes have a borehole, well or spring, or share one with neighbours.
If it's a private supply, jump to Check 5. It's the biggest single water issue a buyer can take on.
Check 2: Buying a house with lead pipes
The Drinking Water Inspectorate says: "Before 1970, lead pipework was commonly used to connect properties to the mains water network." It can still be there — in the pipe from the boundary into the house, in internal pipework, or both.
How to check at a viewing:
Find the internal stop tap, usually under the kitchen sink.
Look at the pipe coming up from the floor. The DWI says: "Unpainted lead pipes appear dull grey and often have a swollen joint next to the tap."
If you're allowed, scratch it gently with a coin. The DWI says that if lead is "gently scraped with a coin, you will see the shiny, silver-coloured metal beneath", and advises: "Wear disposable gloves while you do this and be careful not to breathe in any dust." Copper is "bright, hard and dull brown"; plastic is "typically blue but if older it may be grey or black".
Why it matters: the DWQR says "All drinking water is required to meet the standard for lead (10µg/l) that came into force in December 2013", and that "the people most at risk are children, babies and pregnant women as it impairs development of the child". Replacing the supply pipe is the owner's job; many water companies will replace their section of lead pipe when you replace yours — ask the local supplier.
Check 3: Loft tanks and which taps are mains-fed
In many older homes, some cold taps (often the bathroom) are fed from a cold-water tank in the loft. The Drinking Water Inspectorate advises that, ideally, only mains-fed taps are used for drinking, food and teeth cleaning.
At a viewing or survey:
Look in the loft for a cold-water tank. Is there a tight lid? Are the vents screened?
Ask which taps are mains-fed.
Note it for the future: many buyers remove old tanks when they fit a combi boiler.
See Is UK Tap Water Safe to Drink? for more on bathroom taps.
Check 4: How hard is the water?
Hardness affects kettles, boilers, showers and whether you'll want a softener. There's no health-based limit: the Drinking Water Inspectorate says UK regulations "do not specify standards for hardness, calcium or magnesium". Your water company publishes hardness by postcode. If you fit a softener, keep one unsoftened tap for drinking — for baby formula, the NHS says: "Do not use artificially softened water or water that has been boiled before."
Check 5: Buying a house with a private water supply
If the house has its own borehole, well or spring, ask for:
the source type, depth and location, and who has access to it,
recent test results — ideally an accredited lab report from the last 12 months, including bacteria, nitrate and metals,
details of any treatment (UV, filters, softener) and service records,
the council's risk assessment and any notices, if the council has been involved,
for a shared supply, a written agreement covering access, maintenance and costs,
any history of the supply running low in dry summers.
If the seller can't provide results, make your own test a condition before exchange. See Is Borehole, Well or Spring Water Safe to Drink? and Private Water Supply Maintenance.
Water testing before buying a house: when and which test
Situation | Suggested test | When |
Pre-1970 house on mains | Lead Test (first-draw sample) | Before exchange if you can; otherwise the first week you move in |
Private supply, no recent results | Accredited lab analysis + E. coli Test | Before exchange |
Private supply with recent lab results | E. coli Test as a check | Before exchange or on moving in |
General reassurance | On moving in |
A home test is a screening step. For anything that affects the price or the purchase decision, use an accredited laboratory report.\
Moving into a house that's been empty
Water that has sat in pipes for weeks can taste stale, and in older homes the DWI warns that "Lead from pipework can dissolve into the water whilst it stands in the pipe." On the first day, run every cold tap for a few minutes, starting with the kitchen, and run the hot taps too. If the house is older, test for lead after you've been living there for a few days and the pipes are in normal use.
Selling a house with a private supply
Have a recent accredited lab report, your service records and any council paperwork ready. Buyers' solicitors will ask, and clear records make the sale smoother.
Test your water
Test before you exchange if you can — or in your first week after moving in.
SustainWater home tests are screening tools. If a result is unexpected, or a health, legal or money decision depends on it, confirm it with an accredited laboratory.
Frequently asked questions
Will a homebuyer survey find lead pipes? A surveyor may note visible pipework, but a survey doesn't test the water. Check the pipe at the stop tap yourself and test if the house is pre-1970.
Can I get a mortgage on a house with a private water supply? Often yes, but some lenders ask for evidence that the supply is safe and reliable. Recent lab results help.
Who pays for lead pipe replacement? The homeowner is responsible for the supply pipe within the property boundary and internal plumbing. Many water companies replace their own section for free when you replace yours, and some run lead pipe replacement schemes or grants — check your supplier's website before you book a plumber.
Is it worth testing water before buying a new-build? Rarely for lead. Most new builds are on mains supply with modern plumbing. A general screen can still give peace of mind.
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