A sewer easement is a special type of property ownership that allows a person the right to place a sewer on a small piece of land owned by someone else. Sewer easements are common because often a homeowner or property owner will need to run a sewer line through someone's property in order to have access to the public sewer line. Without a sewer easement, it might be impossible to connect the sewer lines to public sewers, making the property that cannot access the sewer far less valuable.
An easement, in general, is a formal legal term that means a right of passage is granted. When a person owns land, they normally own the full rights to that land, and can prevent other people from passing through or using it. An easement grants another person partial access to a portion of that land for a specific purpose, without the owner's permission.
An easement can be purchased or given. Formal easements can be created by signing a document vesting legal rights in the easement to the person who builds the sewer. An easement can also be created by implication; for example, if one party has been using a driveway on someone else's land for the past thirty years, he or she may have an implied easement to continue using that driveway.
When there is a formal easement, such as a sewer easement, the person who buys the property that the sewer easement is on, buys it with that easement attached. This is extremely helpful to the person who needs the sewer easement. If a homeowner needs to go through his neighbor's yard to reach a public sewer line, it is important to establish a formal written sewer easement that gives him the legal right to have the sewer on the neighbor's property.
If the party requiring the easement does not have a formal easement, but his sewer happens to be on his neighbor's property, he could potentially have problems when the property owner sells the house. If a new buyer purchases the house and does not want the sewer to run through his land, the new owner could demand that the sewer owner remove the sewer line from the property if there is no easement. If there is an easement, however, that easement goes with the property when they buy it, since the sewer owner legally owns the right to run that sewer line through the land.