Inflow & Infiltration

Inflow and infiltration happens when water from the environment unnecessarily enters the wastewater collection system for treatment.


    Photo Credit: King County


Did you know that a recent comprehensive evaluation of the Arthur Wastewater Treatment Plant indicates that per capita, flow of wastewater from the residents of Arthur exceeds the average within the Grand River Conservation Area by almost 2.5 times?

What does this mean to Wellington North? Inflow and Infiltration is restricting growth in Wellington North and is costing residents thousands of dollars annually as ground water and rain water is unnecessarily processed through the Township’s Wastewater Treatment Plants.

Here’s what you need to know about Inflow and Infiltration:

What is Inflow?

Inflow refers to water from rain and snowmelt that inappropriately drains into the wastewater collection system. Typical sources are through sump pumps, roofing, downspouts and basement drains still connected to the wastewater collection system instead of the storm sewer.

Storms or snow thaws bring large volumes of water into the system through:

  • Downspouts
  • Weeping tiles/foundation drain
  • Yard drains
  • Leaky manhole covers
  • Cross connected storm lines

What is Infiltration?

Infiltration refers to groundwater that leaks into the wastewater collection system through cracked, faulty or broken sewer pipes. These pipes may leak because of careless installation, ground movement, and heavy vehicle traffic above sewer line or degradation of sewer piping.

High groundwater or water remaining in the soil after rain or snow could infiltrate wastewater lateral or mainline pipes, pipe joints and other parts of the wastewater collection system that might have deteriorated, cracked, sagged, or collapsed. This water seeps into the system from the surrounding soil.

Why is Inflow and Infiltration a Problem?

Inflow and infiltration are problems because they:

  • Reduce the capacity of the wastewater treatment plant leaving less for existing residents and future growth
  • Higher treatment costs because the wastewater treatment plants wil be required to treat a higher volume of flow
  • Inflow and infiltration contribute to wastewater collection system overflows into homes and local water ways, negatively impacting public health and the environment


Trouble Signs of Inflow and Infiltration in the System   

When all of the extra storm water from inflow and infiltration flows into the wastewater collection system, problems occur that can raise the cost of living for Wellington North residents and put a burden on the communities infrastructure and treatment facilities.

Examples of trouble signs of Inflow and Infiltration are:

  • Greater than anticipated wastewater flows measured at wastewater treatment facilities
  • Wastewater overflows or by-passes at pump stations and wastewater treatment facilities
  • Surcharging of manholes resulting in a loss of pipe capacity
  • Basement flooding during and after rainfall events

Reducing extraneous storm water flows from the wastewater system will help address health, environmental and economical issues associated with overloading the sanitary sewer.

There are three major consequences of too much storm water entering the sanitary sewer system:

  1. Cost - Storm water does not require the same level of treatment as sewage does. When storm water enters the wastewater collection system, it must be handled in the same manner as sewage; it must be transported and treated which costs Wellington North water and sewer rate payers money.
  2. Overloading - An improperly connected sump pump or drainage system into the sanitary sewer system delivers a much higher inflow of water during a storm. This may overload the wastewater collection system and increase the risk of wastewater backup into individual residences.
  3. Environmental Impact - Overflows of untreated or partially treated wastewater at pumping stations and wastewater treatment facilities have a negative impact on the very environment that we as Wellington North residents share.

What can you do as a Resident of Wellington North to Reduce Inflow and Infiltration?

Inflow and infiltration is consuming a large fraction of existing Wastewater Treatment Plant capacity – here are tips for the residents of Mount Forest and Arthur to aid in reducing the capacity:

  1. Disconnect Downspouts - Rainwater runs off a roof, flows through the eavestroughs and downspouts and should discharges  onto your property. The downspout should not be connected to a pipe taking it directly to the wastewater collection system.  During heavy rainfall, if the downspout is connected directly to the wastewater collection system the sewers may become overloaded, therefore increasing the risk of basement flooding, releasing polluted rainwater into our local waterways and sending unneeded water to our Wastewater Treatment Plants for treatment. Disconnecting your downspouts will help reduce the amount of stormwater sent through the wastewater collection system. If you are unsure if your downspout is connected to the Township’s sewer system, contact the Water and Sewer Department (519-848-5327) and they will help assess your connections.
  2. Disconnect Sump Pumps - Sump pumps are designed to capture surface or ground water that enters basements or crawl spaces and pump it away from the house. The basic sump system includes drain tile, a sump pit, a sump pump, a float or switch, a drain line and a check valve. The sump pump pit extends below the basement slab and collects surface water that enters around the basement/crawl space foundation or groundwater that rises to the slab. Sump pumps should not be connected to the wastewater collection system. Sump pumps should drain into the Township’s storm sewer through one of two methods: a direct connection (a pipe from the house to the main storm sewer line), if available, or directly onto the ground (preferably 10-20 feet from the house and not directed into a neighbour’s yard or over a sidewalk). Sump Pump Basics
  3. Use Less Water - Using less water, keeping rainwater on your property and managing what and how much goes into our storm sewer system means you are protecting your home and the environment at the same time.
  4. Recognize -Sewer backup incidents and costs of treating wastewater will be reduced ONLY if everyone’s stormwater is kept OUT of the wastewater collection system.

What are Township Council and the Public Works Department doing about it?

Council and Public Works efforts include building public awareness as it relates to inflow and infiltration. Consideration is also being given into implementing efforts to reduce our inflow and infiltration levels in Mount Forest and Arthur.

View Public Works Committee Meeting of November 18, 2014, WSS 2014-01 Arthur Wastewater Inflow and Infiltration Recommendation Report