Street Trees and House Sewer Laterals
Homeowners often engage in a type of “chicken or the egg” discussion concerning the roots of their street trees and the effect of these roots on their sewer lateral – the pipe that connects the home’s wastewater drainage system to the sewer in the street. You may have heard a neighbor claim that the roots of the tree in front of their house broke through their lateral pipe, causing the pipe to eventually block up so that problem-free flushing became a fond memory.
Tree roots can find their way into a sewer lateral, but normally that occurs
only after the lateral has begun to deteriorate as a result of age, settlement
or other factors. Most of a tree’s root system is concentrated in the top
12 – 24 inches of soil directly beneath the concrete sidewalk. A home’s sewer
lateral, beneath the sidewalk slab, is an average of six to seven feet below
ground, providing a buffer of soil and fill between the lateral and the tree.
The brown pipe connecting the house to the sewer in the street is the house sewer lateral. The blue pipe connecting the house to the street is the house water service. Note that the sewer lateral is approximately six feet below the sidewalk and that the roots of the tree are approximately two feet below the sidewalk
When roots are adventurous enough to find their way to the lateral, it is usually a result of a crack or open joint in the pipe that allows water to escape into the surrounding soil, attracting stray tree roots. Following are a few additional facts to set your mind at ease when contemplating your own street tree:
• House laterals in Philadelphia are made from cast iron. Pipes of this material
usually last 60 – 70 years. This is based upon average Philadelphia weather
(its freeze and thaw cycles), urban loads in streets (cars and trucks), the
nature of sidewalk/street fill and electrical currents in the ground. Older
homes, built prior to World War II, may have had terra cotta lateral pipes.
• Street trees in the City are approved by the Fairmount Park Commission
to ensure that only trees that are suitable to urban environments (trees that
can withstand urban challenges such as pollution and sidewalks and streets
that are filled with infrastructure) are planted along city streets.
• Plumbers have the ability to check the condition of house laterals without
digging up the pipe, if they need to look for blockages caused by roots or
other materials. In addition, commercially available products exist that can
be poured into your toilet and flushed into your pipe, destroying any roots
that may have found their way into the pipe via a crack. Use these materials
only when the weather is dry, as combined sewers may discharge to a river
or stream if they are filled to capacity due to storm conditions.
Trees are Good for your House and the Environment:
• A 2005 Study by the University of Pennsylvania found that trees translated
into higher property values. The study found, for example, that planting a
tree within 50 feet of a house increased its sale price by nine percent.
• Trees provide a cooling shade to a home in the hot summer months, decreasing
the amount of energy required to cool a home and the related electric bills.
Tree lined blocks can actually decrease local temperatures.
• Trees naturally clean the air of pollutants and create a neighborhood
noise buffer
• Trees improve stormwater management, reducing the amount of polluted
stormwater runoff that normally would go directly into storm drains. The leaves
of trees capture rain drops before they hit the ground, evaporating some of
this rain water and sending it back into the air. Tree roots allow rainwater
to filter back into the soil, recharging the often thirsty earth.
Your House Lateral and You
Property owners are responsible for the care and maintenance of their
house lateral, from the point it leaves the property to its connection into
the city sewer in the street. PWD has a Homeowner’s Emergency Loan Program
(HELP) in place to assist residents with the cost of repairing a broken sewer
lateral (the average replacement cost is $3,000). If you receive a notice
from PWD about a broken lateral or water service, call the number on the notice
– 215-685-4900. For water or sewer emergencies, or for general information,
call PWD’s hotline at 215-685-6300.
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