Municipalities around the world are exploring ways to reduce the impact of I&I.   The following are examples of tools and techniques being used for inflow and infiltration reduction and control:

1. Replacing or rehabilitating the defective sewer pipe, lateral and/or manhole.
2. Pipe grouting/sealing – using a cement-based or other material to fill a hole or crack in a pipe or manhole.
3. Pipe relining – inserting a flexible liner into a defective sewer pipe or sewer service lateral which hardens into an impervious surface.
4. Disconnecting known inflow sources, such as cross-connected catch basin drains, footing drains or downspouts.
5. Installing drainage systems that will allow cross-connected sewers to be separated.
6. Backflow valve (or other plumbing upgrade) installation.
7. Storage tanks for capture of  peak wet weather flows.

Some I&I reduction programs that have been proven to be most cost effective are described further below:

Disconnecting Downspouts
Downspouts of many older buildings are connected directly to the wastewater system. In these cases, roof runoff is a significant source of inflow into the system. Disconnecting downspouts can dramatically reduce the volume of water entering the system and can help to minimize peak flows. Where possible, downspouts should be redirected to a stormwater system or disconnected and allowed to discharge to the ground or some type of storage device such as a rain barrel.

The disconnected downspout should direct water away from the building foundation such that there is no property damage or flooding. A splash block or similar feature is generally installed to prevent erosion. After disconnection, the portion of the downspout drain that remains below grade and connected to the sewer lateral should be suitably plugged to avoid subsequent infiltration.

Disconnecting Sump Pumps
Sump pumps used to drain basements are another common source of inflow into sanitary sewer systems.  Sump pumps can be disconnected from the sanitary sewer system and redirected to a storm drainage system, the backyard or garden. Consideration should be given such that discharges are redirected properly in a manner that prevents property damage, erosion or recirculation of the water.

Uncapped Cleanouts
Cleanouts installed on sewer laterals which have become uncapped, have loose or broken covers or are improperly installed can allow storm water into the sewer system. Installing properly sealed covers can remove this source of inflow. This activity can easily be completed by homeowners.

Additional I&I Mitigation/Reduction Programs

Rain Barrels
Rain barrels (or cisterns) are above ground water storage vessels that capture the runoff from home and building roofs. Flows collected in roof gutters are conveyed through the downspout into the rain barrels. Water stored in the rain barrels can be used at a later time to irrigate gardens, lawns or other landscaping. Rain barrels reduce runoff, increase natural infiltration and reduce direct flows into the sewer system. Rain barrels are limited in that they can only store small amounts of water and might not be adequate to store runoff volumes from heavy storms or from prolonged or closely spaced rain events.

Green Roofs
A green roof replaces traditional roofing with a living environment of plants and soil. Among the many benefits they offer, green roofs remove pollutants from stormwater and reduce the amount of water that flows into sewer systems. The plants store excess carbon from the atmosphere, reduce radiant heat in the summer and create habitats for local wildlife. Additionally, green roofs provide extra insulation to buildings. They are designed to intercept rainfall, delay runoff peaks, and reduce runoff discharge rates and volume. Existing buildings can be retrofitted with green roofs and new buildings can be designed to incorporate green roofs. Green roofs have been commonly installed on flat and low pitched roofs on institutional, commercial and industrial buildings; however residential applications are gaining wide acceptance.

Constraints associated with green roofs include the fact that they are limited to use in buildings and roofs which have the structural capacity to support the additional loads.

Pervious Pavements
Pervious concrete pavement is a unique and effective means to address storm water runoff issues. By capturing stormwater and allowing it to infiltrate into the ground, porous concrete promotes groundwater recharge and stormwater runoff reduction. This pavement technology creates more efficient land use by reducing the need for retention ponds, swales, and other stormwater management devices.

Pervious pavement is designed to allow percolation and infiltration of rainfall and snowmelt to the soil underneath it, thereby reducing runoff.

Infiltration Swales
Infiltration swales (also referred to as grass swales) are engineered landscape features that increase storm water infiltration into the native soil structure below. They are typically constructed as linear, shallow open channel areas with flood tolerant, erosion resistant plants. They are designed to convey storm water runoff at fairly slow velocities and at a controlled rate, thereby allowing infiltration to occur. Infiltration swales are commonly used in controlling runoff from highways, roadways, parking lots, at property boundaries. Infiltration swales can be used in place or in combination with traditional curb and gutter. They present an environmentally friendly and aesthetically pleasing solution for controlling storm water runoff.

Rain Gardens
Rain gardens are typically used in controlling runoff from houses and small buildings. These are specially designed gardens containing plants and grasses that can survive in soil soaked with water from rain storms. In addition to collecting and slowing storm water runoff and increasing infiltration, they provide a low maintenance, attractive addition to properties. They can help in reducing basement flooding and eliminate wet spots or standing water in yards and landscaped areas.

Rain gardens are limited in that they are appropriate only for small drainage areas. Plants and grasses for the rain garden have to be carefully chosen to withstand soaked conditions.

Underground Storm Water Storage
Underground storm water storage systems capture and store storm water runoff from surrounding impervious areas. Stored water is released from storage back into wastewater system at a controlled rate, thereby, delaying runoff peaks and reducing discharge rates. Underground storage systems are often used in high density urban areas with limited space or where land is expensive and other surface storage runoff control methods are not feasible.