How your sewer works
Before reading the following section, please note this is a guideline related to how a home's plumbing system basically operates. The intent of this section is to provide a general overview of plumbing components, their purpose and how they work. This information is not intended to be used for construction or as a guide for installing piping. Particular details regarding any plumbing work you are about to undertake or have begun should be directed to the Plumbing Inspections Branch with the City's Community Services Group.
There are several main components related to a home's plumbing system. In addition, homes have changed throughout the years with improvements made as a means to better collect drainage and outlet wastewater. A home built in 1920 will have a different plumbing configuration than a modern house; however, there will be some basic similarities. Understanding how your home's plumbing system works will help identify potential problems and allow you to discuss piping remedies with a private plumber or a drainage contractor. Please keep in mind that piping on private property falls under the jurisdiction of the Community Services Group, formerly Permits & Licenses.
To start, sewers work on the basic principle of gravity. Adequate flow-rate for sewer and drainage is based on the formula of rise over run or slope over distance. A 2% grade or .25" (6mm) of fall over a distance of one foot is the minimum standard for laying wastewater piping. A 1% grade or .125" (3mm) over the distance of one foot is the minimum standard for laying storm-water pipes.
Here are some examples:
- Wastewater piping: 10 feet of pipe will require a minimum of 2.5" or 63mm of fall.
- Storm-water piping: 10 feet of pipe will require a minimum of 1.25" or 32mm of fall.
Some homes have pump systems which are used when basements are located below the collection main and wastewater or drainage needs to be pumped to a chamber or sump where it can flow by gravity to the main at a minimum grade. It is important to maintain pumps regularly to ensure they operate without problems.
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What are the main sewer and drainage components associated with my home?
There are three standard piping systems to familiarize yourself with related to conveying storm and wastewaters. The first component is the downspouts, roof drains or rainwater leaders. The second system is the drain-tile or footing drains, and the third component is the main sewer-line which carries drainage and waste from the home and is then collected in the City sewer-main. See the appropriate house diagram for details.
Downspouts or roof drains
Downspouts or roof drains collect rainwater trapped by the perimeter of the home's roof. Rainwater flows from the eave troughs and exits down a downspout located against the siding of the home. There can be four or more downspouts on a given home. The downspouts are attached to 3 to 4" (75mm,100mm) diameter piping typically buried two to three feet below the ground. The water flows through these pipes to a sump or concrete collection chamber located either inside or outside of the home.
Some older homes do not have piping to intercept water flowing from the roof. This means the downspouts may connect directly into the drain-tile or percolate directly into the ground itself. In some cases, flow of storm-water is directed to a drainage or rock pit.
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Drain-tile or footing drains
The second system to be knowledgeable about
is the drain-tile. Drain-tile, footing drains, or weeping tile all refer
to the short pieces of clay pipe that is placed around the home's perimeter
at the footings of the foundation. The depth of the drain-tile correlates
to the depth of the basement floor. In other words,
if the basement is four feet or 1.2 metres below the ground level, then the
drain-tile would quite likely be 12" to 18" or 30 to 45 cm below the basement
floor depth.
Drain-tile is designed to collect groundwater that seeps through the earth during rainfall or when your garden beds located near the home are being sprinkled. The groundwater trickles to the drain-tile entering the clay tile at the joint. Newer homes do not utilize clay tiles any longer, and plastic polyvinyl chloride (PVC) perforated pipe or perforated PVC drainage tubing is now typically installed at the footings.
From time to time, especially after many years of use, drain-tile can crack or become plugged with debris. Downspouts connected directly to the drain-tile will sometimes carry sediment and rotting leaves which have landed on the roof. Soil can also build up in the drain-tile. The consequence of non functioning drain-tiles might be water leaching or seeping through the porous concrete foundation or leaving a damp mark on the basement floor or foundation wall. Often a repair to the section of tiles or a flushing will alleviate the problem. Replacement of the old clay drain-tile can be considered but not necessarily required.
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The sump
Flow from drain-tiles and downspouts link up at a concrete square or cylindrical chamber referred to as a sump. Some homes have sumps located inside the basement or outside under the front steps, porches, or some place in the yard. Sometimes sumps are covered over with flooring and cannot be easily located inside the home. Occasionally, unsuspecting homeowners find their sumps by accidentally stepping through a rotten planked lid that has been buried under the lawn for many years.
If a sump is located outside the house, it is usually situated not too far away from the home. The plumbing inspections branch may have a sump permit on hand which can help as a clue if you are searching for the sump. Keep in mind some older homes do not have sumps. Contact the inspections branch at 604-873-7601 and find out how to initiate a search for a sump permit for your address. There may be a small charge associated for this service.
The
drawing on the right is intended for general informational purposes only.
Actual details regarding sump specifications, placement, and regulations
must be directed to Plumbing Inspections: 604-873-7601.
As previously noted, the sump primarily collects storm-water from the drain-tile and from the roof drains. The flow drains into the sump via two inlets and then exits from an outlet pipe after the water level in the sump reaches a certain elevation. The outlet pipe has a 90 degree bend referred to as a goose neck. On the downstream side of the goose neck, is a backwater valve designed to stop sanitary flow from backing up into the sump. If the plumbing system of the home is considered combined, meaning both storm and waste-waters eventually tie together, the outlet pipe from the sump will connect to the main sanitary line several feet or metres downstream of the sump.
Even in dry weather, there should be water in the sump at a level of just above the "goose neck". The water acts as a lock or barrier for sewer gases which sometimes vent from the sewer-main back to the home. If you ever smell a rotten egg like sewer smell in your basement, possibly the result of hydrogen sulphide, check the level of water in your sump to see if there is an air gap between the surface of water and the goose neck. Fill the sump with water from a hose and replenish the level until it begins draining out the sump outlet. Backwater valves should be checked annually to see whether they are functioning properly. Unscrew the top cap of the backwater valve to insure the flapper is correctly seated and can shut in cases of backflow from the main sewer-line. Summertime is a good time to inspect your sump.
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The main sewer-line
The main sewer-line carries all grey and black water from the home and in older homes, the storm waters as well, to the City connection and City sewer-main. Grey water is discharged from sinks, tubs, floor drains, dishwashers and washing machines. Black water refers strictly to sewage.
The grey and black water piping system is a maze of small diameter pipes connecting together inside the home and routing to a vertical 4" or 100mm pipe recognized as a stack. From the stack, which also acts as a vent for air trapped in the pipes, the wastewater exits to the main sewer-line which is typically located underneath the basement floor slab.
The portion of main-line situated underneath the concrete slab is composed of cast iron, as a means to handle the weight of the home. The pipe material changes from cast iron to vitrified clay short length pipe once the main pipe exits from under the home and is no longer burdened by the weight of the house.
The main sewer-line typically travels past the sump and collects the storm-water flow from the sump and conveys combined flow (both waste and storm-waters) to the City connection and City main.
Newer homes, those built after 1985, and some older homes within pockets of the City have a slightly different piping configuration whereby the storm-waters do not discharge together with the sanitary flow. These homes have a separated piping system. This is the case when two main pipes discharge separate storm and waste waters from the home.
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