Building an extension, renovating a property or installing a new driveway should improve your home, not leave you dealing with blocked drains, standing water or unpleasant smells.
Unfortunately, drainage problems can sometimes appear shortly after construction work finishes. Excavation, changes to ground levels, damaged underground pipes and poorly connected drainage can all affect how wastewater and rainwater move around a property.
At Pure Drainage, we help homeowners across Southampton identify the causes of drainage problems through CCTV drain surveys, inspections and professional repairs.
How Can Building Work Affect Existing Drains?
Underground drainage systems can be more vulnerable to damage during construction than many homeowners realise.
Digging foundations, moving heavy machinery and installing new services can disturb existing pipework. Even when the surface looks perfectly finished, problems may be developing underneath.
This is particularly worth considering in established Southampton neighbourhoods such as Shirley, Portswood, Bitterne, Woolston and Freemantle, where older properties may have undergone several extensions or renovations over the years.
Common Drainage Problems After Construction
1. Damaged Pipes During Excavation
Underground pipes can be accidentally cracked, crushed or displaced during groundwork. A damaged pipe may continue working initially, only to develop recurring blockages as waste catches on the affected section.
Where structural damage is found, professional drain repairs may be needed to restore the system.
2. Incorrect Drainage Gradients
Wastewater pipes need an appropriate gradient to allow water and waste to flow effectively.
If new pipework has been installed with insufficient fall, or an existing drain has shifted during construction, water may collect inside the pipe instead of flowing away.
This can lead to slow drainage, unpleasant smells and repeated blockages.
3. Building Debris Entering the Drains
Sand, mortar, cement residue, soil and rubble can sometimes enter drainage systems during renovation work.
These materials can settle inside pipework and create stubborn obstructions. Depending on the condition of the drain and the material involved, professional cleaning or high-pressure drain jetting may help restore normal flow.
4. Changes to Surface Water Drainage
Extensions, patios and driveways change how rainwater moves around a property.
Replacing lawns or soil with impermeable surfaces can increase runoff. If the existing drainage system has not been adapted, rainwater may begin collecting around foundations, doorways and paved areas.
In some cases, additional surface water drainage or soakaway installation may be appropriate, depending on ground conditions and the property layout.
Warning Signs to Look Out For
If drainage problems started shortly after building work, keep an eye out for:
- Sinks, showers or toilets draining more slowly than before
- Gurgling noises from pipework
- Recurring blockages that were not previously an issue
- Water pooling near new extensions or patios
- Foul smells around external drains
- Sunken paving or unusually damp ground
These symptoms do not automatically mean the building work caused damage, but they provide a good reason to investigate.
What About Building Over Existing Sewers?
Homeowners planning extensions should also consider whether public sewer infrastructure runs beneath or close to their proposed building work.
Southern Water advises that building within three metres of a public sewer generally requires its permission through a build-over application.
You can read its guidance on building over or near public sewers for further information.
Southampton City Council’s building control guidance also highlights the importance of considering drainage and nearby sewers when planning extensions.
If problems arise after construction, checking the original drainage plans and any relevant approvals can help establish how the system was intended to work.
How Are Drainage Problems Investigated?
The best starting point is usually to establish what has changed and where the problem is occurring.
A CCTV drain survey allows engineers to inspect underground pipes for cracks, displaced joints, construction debris and other defects without immediately excavating the surrounding area.
Once the cause is identified, the appropriate solution might involve clearing a blockage, correcting a drainage connection, repairing damaged pipework or replacing a section that has been incorrectly installed.
Pure Drainage also provides excavation and groundworks services where more substantial repairs are necessary.
Drainage Problems After Building Work in Southampton?
If your drains have started blocking, smelling or overflowing following an extension, renovation or groundwork project, getting the system inspected can help prevent further disruption.
Pure Drainage provides drainage inspections, CCTV surveys, drain repairs and groundworks across Southampton and surrounding areas, including Totton, Hythe, Eastleigh, Hedge End and the New Forest.
Contact Pure Drainage today to arrange an inspection and find out what’s causing your drainage problems.
Do you need help from our experts?
Give us a call today to get expert advice and support from our experienced team.