2026 has already been a record-breaking year for UK weather, and it’s starting to show up underground too. According to the Met Office, temperatures of 35C or higher have now been recorded in May, June and July of the same year for the first time in the UK weather record, with a run of eight days above 34C beating the previous record set in 1976 and 2020. On 9 July, Wisley in Surrey recorded 35.5C. That kind of sustained heat is starting to cause a specific and often overlooked problem: heatwave drain damage.
For facilities managers and commercial property owners, the headlines have understandably focused on health warnings, wildfire risk and travel disruption. But sustained extreme heat has a slower, less visible effect too. It changes conditions underground, and that has consequences for drainage systems that are often only noticed once a problem has already developed.
Why heatwaves affect drains as much as storms
Drainage systems are usually associated with rainfall, not sunshine. But prolonged dry heat creates its own set of risks, particularly for older commercial and industrial sites with extensive underground pipe runs.
- Ground shrinkage and pipe movement. Clay-rich soils, common across much of Hampshire, Surrey and the wider South East, shrink significantly as they dry out. This movement can open up joints in older pipework or crack pipes that were previously stable, allowing wastewater to escape into the surrounding ground.
- Root ingress. As surface moisture disappears, tree and shrub roots are drawn toward the moisture inside drainage pipes, often forcing their way through minor cracks or joints in search of water. This is one of the most common causes of blockages reported after extended dry spells.
- Reduced flow and increased blockages. With less rainfall entering the system, foul drains carry a higher concentration of waste relative to water. This can lead to more frequent blockages, stronger odours and increased strain on pumps that rely on a certain volume of flow to operate efficiently.
- Pump station strain. Pump stations serving commercial sites, holiday parks and managed estates often work harder in hot weather due to increased water usage (irrigation, cooling systems, higher occupancy) combined with reduced natural flow, raising the risk of a fault going unnoticed until it fails.
The human cost shows how serious this year has been
This year’s heat isn’t just a talking point for facilities teams. Research from Imperial College London, the Met Office and the London School of Hygiene & Tropical Medicine estimated more than 2,700 heat-related deaths in England and Wales during the May and June heatwaves alone, with climate change adding 3-4C to peak temperatures and accounting for around 42% of those deaths. It’s a sign that this year’s heat extremes are not a one-off, and that the infrastructure underneath our sites needs attention alongside the public health advice.
What to check on your site this summer
For commercial and industrial property owners, the practical takeaway is simple: heat-related drainage problems tend to build quietly, and are cheaper to catch early than to repair later.
- Watch for slow-draining fixtures across the site, particularly if several appear at once rather than in isolation.
- Check external paved areas near drain runs for new depressions, cracking or soft ground, which can indicate movement below.
- Note any unusual odours around gullies or manholes during dry weather, a sign of reduced flow or a developing leak.
- Review pump station performance logs if your site has one, and don’t wait for an alarm before scheduling an inspection.
- Book a CCTV drain survey if your pipework hasn’t been inspected in the last few years, especially on sites with mature trees or known clay ground conditions.
How a CCTV drain survey helps
A CCTV drain survey is a non-invasive way to inspect the full length of a pipe run and identify cracks, joint displacement, root ingress or early signs of deformation before they become a bigger problem. It produces a documented report that’s useful for planning repairs and, where relevant, supporting insurance discussions.
Drain & Sewer Services carries out CCTV drain surveys and drain repair work across commercial, industrial and managed sites in Hampshire, Surrey, Berkshire and the surrounding areas, using specialist crawler systems for larger-diameter pipes. If this summer’s heat has you wondering about the condition of your drainage, a survey is the fastest way to get a clear answer.
If you’ve noticed any of the signs above on your site, get in touch and we’ll arrange a survey before the problem gets worse. Call us on 01252 312738 or email info@drainandsewer.co.uk.
Frequently asked questions
Can hot weather really damage drains?
Yes. Prolonged dry heat causes clay soils to shrink, which can open joints or crack pipes that were previously stable. Reduced rainfall also lowers flow through foul drains, increasing the risk of blockages and odour issues.
Is this year’s heat actually unusual, or does this happen every summer?
2026 has been exceptional. The Met Office confirms it’s the first year on record with temperatures of 35C or higher in May, June and July, and the first time eight days above 34C have been recorded in a single year, surpassing the previous record from 1976 and 2020.
How do I know if my drains have been affected by ground movement?
Signs include slow drainage across multiple fixtures, new cracking or soft patches in paved areas near drain runs, and unusual odours during dry weather. A CCTV drain survey is the most reliable way to confirm whether pipework has been affected.
When is the best time to book a drain survey after a heatwave?
As soon as possible after signs appear, and ideally before autumn rainfall arrives. Ground that has shrunk over summer can shift again once it rehydrates, which can turn a minor crack into a more significant fracture.
