Manhole Sealing Services: Inspection, Infiltration and Repair

Updated: 11 September 2026

Manhole Sealing & Infiltration Repair: How Leaks Are Found and Repaired

Manhole infiltration occurs when groundwater or surface water enters a drainage or sewer system through cracks, joints, pipe connections or defects in the chamber structure.

Left unresolved, infiltration can increase the amount of unwanted water entering the drainage network and may contribute to deterioration around the manhole structure.

AJS Environmental provides manhole inspection, drainage investigation, sealing and repair support across Essex, London, Kent and Hertfordshire, using survey-led methods to identify where water is entering before deciding how the defect should be treated.

What Is Manhole Infiltration?

Infiltration is the movement of unwanted external water into a drainage or sewer system.

This water can enter through:

• Cracks in chamber walls
• Defective construction joints
• Pipe connections
• Open or deteriorated brickwork joints
• Damaged benching
• Defects around the chamber base
• Movement between chamber sections
• Other structural openings

The amount of infiltration can vary significantly depending on groundwater levels, rainfall, surrounding ground conditions and the severity of the defect.

Why Is Manhole Infiltration a Problem?

Unwanted water entering a drainage system can create several operational problems.

Depending on the network, infiltration may:

• Increase the volume of water moving through the drainage system
• Reduce available capacity during wet weather
• Increase loading on downstream drainage infrastructure
• Indicate deterioration in the chamber structure
• Allow surrounding material to wash through defects in some conditions
• Contribute to recurring maintenance requirements
• Make inspection and repair work more difficult

For commercial, industrial and public-sector drainage systems, identifying the source of infiltration can form part of wider condition assessment and maintenance planning.

Where Does Water Enter a Manhole?

There is no single infiltration point common to every chamber.

Water may enter through:

• Construction joints
• Precast concrete section joints
• Brickwork and mortar joints
• Pipe penetrations
• Cracks in the chamber wall
• Benchings and channels
• Chamber bases
• Areas affected by settlement or movement
• Frame and cover areas where surface-water entry occurs

This is why simply applying a sealing product without identifying the source may not resolve the underlying problem.

How Is Manhole Infiltration Identified?

Some infiltration points are immediately visible during inspection.

Signs may include:

• Visible water entering through a joint
• Constant damp patches
• Running water on chamber walls
• Mineral staining
• Deteriorated mortar
• Cracks around pipe entries
• Movement between chamber sections
• Standing water where it should not normally be present

Where the surrounding drainage condition is uncertain, a CCTV drain survey can also help determine whether connected pipework contains cracks, displaced joints, root ingress or other defects. AJS’s current CCTV service is designed to identify internal drainage defects before repair decisions are made. :contentReference[oaicite:1]{index=1}

Manhole Inspection Before Sealing

The purpose of inspection is to determine whether the manhole can be repaired locally or whether a wider structural issue exists.

The engineer may assess:

• Chamber construction
• Condition of joints
• Visible cracking
• Pipe connections
• Benching condition
• Signs of movement
• Water-entry points
• Condition of the cover and frame
• Access and working-space requirements

Not every leak should be treated in exactly the same way.

How Is a Leaking Manhole Sealed?

The repair method depends on the defect and chamber material.

Possible treatments may include:

• Localised joint sealing
• Repair of cracks
• Sealing around pipe penetrations
• Repair of damaged mortar or chamber surfaces
• Specialist sealing compounds
• Localised structural repair
• More extensive chamber rehabilitation where deterioration is widespread

The repair surface normally needs to be prepared appropriately so the selected material can bond and perform as intended.

What Is a Manhole Chimney?

The upper section of a manhole between the chamber and the cover/frame is sometimes referred to as the manhole chimney.

This area can be exposed to:

• Surface-water entry
• Ground movement
• Traffic loading
• Deteriorating joints
• Movement around the cover and frame

If water is entering at the upper part of the chamber, sealing or repair may be required around the affected joints or structure.

However, the source should be confirmed before assuming the chimney is responsible.

Manhole Sealing Around Pipe Connections

Pipe penetrations are another common area requiring inspection.

Movement, poor historic sealing, deterioration or construction defects can leave gaps between the pipe and chamber wall.

These areas may allow groundwater to enter or can indicate deterioration around the connection.

Where appropriate, the affected area can be prepared and sealed using a suitable repair system.

Cracks in Manhole Walls

Cracking can vary from superficial surface damage to more significant structural deterioration.

Before sealing a crack, it is important to consider:

• Whether the crack is active or stable
• Whether there is movement
• Whether groundwater is entering through it
• Whether the chamber wall remains structurally sound
• Whether a local repair is sufficient

A crack caused by ongoing movement may require more than a simple surface seal.

Manhole Infiltration and Connected Pipework

Sometimes the water visible in a manhole is not entering through the chamber itself.

It may be arriving through connected drainage because of defects further upstream.

Possible causes include:

• Cracked pipes
• Open joints
• Root ingress
• Damaged lateral connections
• Groundwater entering through defective pipework

In this situation, sealing the chamber alone would not address the actual source.

CCTV investigation can help determine whether connected pipework also requires repair.

Can UV Drain Lining Help With Infiltration?

If infiltration originates from suitable defects within connected pipework rather than the chamber itself, UV drain lining may be considered where the pipe condition is suitable.

AJS Environmental’s current UV process includes CCTV diagnosis, cleaning and preparation, robotic preparation where necessary, liner installation, UV curing and post-repair CCTV verification. :contentReference[oaicite:2]{index=2}

However, UV lining is a pipe rehabilitation method and should not automatically be treated as the solution for every leaking manhole.

Can Manhole Infiltration Be Completely Stopped?

Local sealing can be very effective where the source of infiltration is identified and the surrounding structure is suitable for repair.

However, it is better to avoid absolute guarantees because:

• Groundwater conditions can change
• Additional defects may exist elsewhere
• Structures can continue to move
• Multiple infiltration paths can be present
• Connected drainage may also contribute

The objective should be to identify and repair confirmed entry points and then verify the result.

What Happens During a Manhole Sealing Project?

When Should a Manhole Be Investigated?

Investigation may be appropriate where there is:

• Visible groundwater entering the chamber
• Persistent dampness or running water
• Recurring drainage overload
• Cracking or deterioration
• Movement around chamber joints
• Leaking pipe connections
• Unexpected water levels during dry conditions
• Suspected defects before wider drainage rehabilitation

Commercial and Infrastructure Manhole Sealing

Manhole infiltration can affect many different types of site, including:

• Commercial premises
• Industrial estates
• Retail parks
• Schools
• Housing developments
• Highways drainage
• Public-sector estates
• Large private drainage systems

AJS Environmental supports drainage investigation and repair work across Essex, London, Kent, Hertfordshire and surrounding areas. The company’s wider services include CCTV inspection, UV lining, robotic cutting, Jet Vac cleaning and drainage maintenance. :contentReference[oaicite:3]{index=3}

Related Drainage Services

• CCTV Drain Surveys
• UV Drain Lining & No-Dig Repair
• Robotic Drain Cutting
• Blocked Drain Services
• Drainage Services & Areas Covered

Manhole Sealing & Infiltration FAQs

What is manhole infiltration?

Manhole infiltration is the unwanted entry of groundwater or surface water into the drainage system through cracks, joints, pipe penetrations or other defects in the chamber.

What causes water to enter a manhole?

Common causes include cracked chamber walls, defective joints, failed pipe seals, damaged brickwork, movement between chamber sections and high groundwater levels.

Can a leaking manhole be sealed?

Yes, many localised infiltration defects can be sealed or repaired. The correct method depends on the chamber material, defect type and structural condition.

Can manhole sealing stop groundwater entering?

It can stop or reduce infiltration through confirmed defects where the surrounding structure is suitable for repair. Other entry points may also need to be identified and treated.

What is a manhole chimney?

The manhole chimney is the upper section between the main chamber and the cover/frame. Joints and movement in this area can sometimes allow water to enter.

Can water enter through pipe connections?

Yes. Deteriorated or poorly sealed pipe penetrations can provide a route for groundwater to enter the chamber.

Do you need CCTV before manhole sealing?

Not always. Visible chamber defects can sometimes be assessed directly. CCTV is useful where connected underground pipework may also be contributing to the infiltration problem.

Can damaged pipework cause apparent manhole infiltration?

Yes. Water may enter the drainage system through defects in connected pipes and then appear within the manhole. This is why the wider drainage condition may need investigation.

Can a badly damaged manhole always be sealed?

No. Severe cracking, structural movement or extensive deterioration may require more substantial rehabilitation or reconstruction rather than local sealing.

Where does AJS Environmental provide manhole sealing services?

AJS Environmental provides drainage investigation and repair services across Essex, London, Kent, Hertfordshire and surrounding areas.