Of all of the various types of connections needed for a house sewer, building a new manhole connection is the most costly to the property owner. A new manhole connection likewise requires the most skill, and typically takes the most time to build. This type of connection is thankfully only required in very specific circumstances. Those circumstances do not involve typical residential properties. That is because manhole connections are only required for house sewers 12″ in diameter or larger. Almost all house sewers are either 6″ or 8″ in diameter. With that said, only extremely large buildings or paved lots would ever require a 12″ or larger house sewer. In some cases two separate house sewers might be installed for a lot to avoid one large sewer, avoiding having to build a manhole connection. Two new sewers can actually be less costly than one large house sewer.
DEP Rules Governing House Site Connections to Sewer System
The NYC DEP has very specific rules and regulations governing house sewer connections. They likewise clearly specify when a new manhole connection must be built. The following is directly out of the DEP Code.
Any sewer connection twelve (12) inches in diameter or larger to existing sewers or drains less than forty-eight (48) inches in diameter shall be made only to an existing or proposed manhole. For sewer connections larger than eighteen (18) inches in diameter, the applicant shall submit a detail of the proposed method of connection to the DEP for review and approval.
(d) Manhole Connections.
(1) The inner top of the proposed sewer connection shall not be lower than the inner top of the sewer. The invert of the proposed sewer connection shall be at least three (3) inches above the bench elevation at the manhole wall. The invert of the proposed sewer connection shall not be more than four (4) feet above the spring line (1/2 the diameter) of the sewer.
(2) The use of pre-cast manholes on existing sewers or drains shall be in conformance with the latest DEP Sewer Design Standards, and shall be supplied by an approved vendor.
(3) No pre-cast manholes shall be installed on existing brick sewers.
Adherence to NYC DEP Code
Before any new manhole connection can be built an Engineer or Architect must submit a plan detailing the method of installation. That plan must be reviewed and approved before a Licensed master Plumber can secure a permit to start work. Once permits are secured, each step of the installation must be inspected before the next step can follow. In the case of an existing clay city sewer there is a 3 step process after the excavation is prepared.
1. Building the base for the manhole
Once the excavation is made and properly enforced to safety code, the base for the extreme weight of the manhole must be poured. This involves setting a form and placing rebar in a pattern that meets the approved plan. The base is then poured using a minimum of a 4,000 PSI concrete mix.
2. Setting the manhole rings
Setting the rings typically involves purchasing precast manhole rings form an approved vendor. A top slag, ring for the manhole, and the manhole cover are also needed. The rings are set in place to closely approximate the desired finished elevation. It is typical for bricks to be used to make the end product align perfectly with the elevation of the surrounding roadway.
3. Making the sewer house connection
Making the actual connection for the house sewer must also follow the approved plan. The house connection is typically just above the flow line of the city sewer. If is usually made by core drilling the required size opening through the new manhole connection itself.
New Manhole Connections Require A High Level of Skill
None but the most highly skilled sewer contractors typically build manholes in NYC. One of the reasons is an extremely careful and multi-step inspection process. A primary reason for that is that after the DEP signs off on the manhole it becomes the property and responsibility to maintain of the DEP. Like all manholes, their primary function is to act a clean-out for future maintenance. The openings in the manhole cover itself act as a way to vent sewer gases.
Call on the Leader in the NYC Industry for Your Sewer Work
Regardless of the skill level requirements for any sewer work you may need, Balkan is the leader in NYC’s sewer and water main industry. Team Balkan has been operating for well over 65 years under the same exact family and company name. That makes us unique in NYC sewer and water main industry. Whether you need prompt expert advice, or a free and no obligation site visit, contact Team Balkan.