City of Monterey - Building Safety & Inspection

Back Water Valves -
Preventing Sewage Backups at Home

Brochure in PDF - printable version
Backwater Valve Lookup - find out if you have a backwater valve
on your property

What is the City’s residential sewer lateral backwater device requirement?

Section 9.1 of the City Code requires both a sewer relief vent (SRV) and a backwater valve (BWV) be installed on your sewer lateral, if the lowest plumbing fixture in your home is lower than two feet above the nearest upstream manhole cover. See illustration #1 below It is also the responsibility of the homeowner to maintain both of these devices so that they operate properly.

Why are they required?

Although the City has an aggressive sewer main inspection and maintenance program, our sewer mains can and do become partially or fully blocked due to roots and/or other debris introduced into the sewage system. When blockages occur in the sewer main, effluent can backup into residential sewer laterals and, if not properly protected, directly into residences.

How does our sewer system work?

In any building, the waste water generated by all the plumbing fixtures is drained through an underground pipe called a sewer lateral and it connects to a large pipe called a sewer main buried in the street. The sewer main drains by gravity. For cleaning and access purposes, manholes are usually located at intersections.
When a blockage occurs in the sewer main it will back up until the effluent spills out of the upstream manhole cover. Buildings which have plumbing
fixtures that are not two feet higher than the upstream manhole cover are subject to having effluent back up through the sewer lateral and into the building if not protected by a backwater valve and sewer relief vent. See illustration #1

What do these devices do?

Sewer relief vent: This device is installed in the vertical position (extended up from a sewer lateral) at ground level to allow effluent to discharge onto the exterior of your property.
See figures 1 & 2 on illustration #2
Backwater valve: This device is installed in the horizontal position in your sewer lateral below the ground and is a one way flap valve which allows the sewage to flow out to the sewer main in normal use, but prevents sewage from backing up into the residence if the sewer main should become blocked. See figures 3, 4 & 5 on illustration #2

Who can install these devices and what does it involve?

It is recommended that a licensed plumber install these devices.
The sewer relief vent is installed at ground level attached to a vertical section of pipe connected to the sewer lateral below the ground. A trench must be dug down to the level of the sewer lateral, the vertical section of pipe installed and then the sewer relief vent installed at the top.
The backwater valve is installed below the ground in the horizontal flow line of the sewer lateral. A trench must be dug down to the level of the sewer lateral, a section cut out and the backwater valve installed. An access box must be built from the ground down to the backwater valve to allow for maintenance and removal of the valve when the sewer lateral is cleaned. The depth of the trench depends on how far below the ground the sewer lateral is located.
See illustration #1

How do I know whether I have both of these required devices? Where do I look on my property for these devices?

To see whether or not a backwater valve and sewer relief vent are needed at your address, or may have already been installed, visit our Backwater Valve Lookup Web page.
If you can locate your sewer lateral and/or clean out plug, look to see if it has a sewer relief vent (illustration #2) installed at ground level somewhere in the route of the sewer lateral from your house to the sewer main. Next look for an access box for the backwater valve (illustration #2) which, if installed, is located below the ground. If you cannot find one or both of these devices you should call a licensed plumber.

What is the process if I choose to install the devices?

Contact a licensed plumber for an assessment and installation of the required devices. A City of Monterey plumbing permit must be obtained prior to installation. The plumbing permit may be issued to the owner of the property or a licensed plumber.

Why does my house need these devices when my house is located higher than the street?

Remember that you must measure the height of your lowest plumbing fixture against the height of the upstream manhole cover, not the height of the street or the underground sewer main in front of your house.

What happens if I don’t install the devices?

If a SRV and BWV has not been installed per the City Code, any costs incurred as a result of a back up will be the responsibility of the homeowner.

How much does it cost?

The cost of installing a sewer relief vent and backwater valve varies with each individual property and depends on several factors:

How accessible is the area where the sewer lateral is located?

Is there a driveway or a patio on top?

How far below the ground is the sewer lateral located?

Why doesn’t the City pay for it?

These devices protect private property and are installed on your private sewer lateral. The city does not pay for improvements made to private properties.

ILLUSTRATION #1

ILLUSTRATION #2
Sewer Relief Vents
figure 1	figure 2
Backwater Valves
figure 3	figure 4
figure 5

Return to Building Safety & Inspection Main Page
Return to top

Rev. 12/20/06 -L. Huelga - http://www.monterey.org/commdevelop/bldgsafety/bwv.html