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Frequently Asked Questions

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Published on November 10, 2016. Last modified on January 26, 2018

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Frequently Asked Questions

An onsite wastewater treatment system (OWTS) is designed to treat and dispose of domestic sewage. The terms “OWTS” and “septic system” are interchangeable. A septic system consists of a tank that receives waste from a residence or business connected to a system of leach fields or seepage pits designed to dispose of the liquid effluent. The sludge that remains on the tank bottom after bacterial decomposition of the solids must be pumped out periodically.

A. A septic tank separates solids (Sludge and Scum) from the liquid wastewater to prevent the disposal field from clogging.

  1. The wastewater slows down when it enters the tank.
  2. Gravity causes the settle-able solids, known as sludge, to fall to the bottom of the tank and out of the wastewater.
  3. Fats, oils and greases, known as scum, float on the top of the wastewater and are blocked from leaving the tank by a baffle.
What is the difference between a diversion valve and a distribution box?

A diversion valve is installed between the primary and secondary disposal fields. The valve directs the wastewater into either the primary or secondary disposal field, never both at once. Utilizing a diversion valve helps to extend the life of your disposal fields because they have an opportunity to dry out or “rest” for a period of time while the other disposal field is in use.

A distribution box is used when multiple lengths of disposal field are combined to comprise a single disposal field. The distribution box ensures that an even flow of wastewater is directed into each length of disposal field.


An effluent filter is installed at the outlet pipe to screen the wastewater as it exits the septic tank. The filter prevents small solids (1/8” and bigger) from leaving the tank, protecting your disposal field from obstructions and clogging. The price of an effluent filter is a fraction of the cost of replacing your disposal field, making it an excellent investment.

A. The purpose of a septic tank is to keep solid mater from moving on to the disposal field and eventually clogging it. Based on the way septic tanks are designed, sludge (settleable solids) and scum (floatable solids) cannot pass through. Once the levels of solids or scum pass a critical point, solid wastes will begin to flow out of the tank and into the disposal field.

Disposal fields that fail due to sludge and scum accumulation often cannot be salvaged or repaired.

As a general rule, you should pump your septic tank every 3 – 5 years to prevent the buildup of sludge and scum from moving out of your tank and into your disposal field. Regularly cooking with fats, greases and oils can accelerate scum layer build up, resulting in the need for more frequent pumping.

Having a certified septic contractor perform an annual septic system inspection keeps your system performing optimally and identifies when your tank needs to be pumped instead of assuming the recommended 3 – 5 years between pumping.

Chemical – A septic tank is chock-full of bacteria that work to break down the solids. Using harsh cleaning products and bleach in the laundry can wipe out the bacteria that are vital to the function of your septic tank. When solids aren’t broken down they accumulate in the tank and eventually flow out to the disposal field. It is difficult to revitalize a disposal field that is matted with solids and often requires complete replacement.

Water – A septic system is sized to accommodate a certain number of people in a home, normally determined by the number of bedrooms. The people living in a 4-bedroom home are expected to generate 375 gallons of wastewater daily, or 75 gallons per person. A single leaky toilet can waste 200 gallons of water a day! That is like having 2 or 3 house guests for each day that the toilet leaks. If a disposal field isn’t sized to handle the extra water, it is likely that before long the wastewater will begin to bubble out of the ground, indicating septic system failure and a public health concern.

Solids – The only way to know if your septic tank needs to be pumped is to have an inspection by a licensed septic system inspector. Annual inspections can identify potential problems and solve them before they happen. Over-accumulation of solids in a septic tank will result in their being flushed out to the disposal field. It is difficult to revitalize a disposal field that is matted with solids and often requires complete replacement.

A. There are many additives available on the market that claim to improve septic system performance or mend a troubled system. There is no evidence or data that proves additives, natural or chemical, improve system function or lifespan.

Annual septic system maintenance performed by a certified septic contractor will help prolong the life of your system. Annual inspections should include:

  • Check integrity of tank walls, lids and risers
  • Ensure integrity of inlet and outlet tees
  • Install, clean or replace effluent filter
  • Measure scum and sludge (solid matter) levels
  • Check for indicators of disposal field backup or failure


YES!! Gray water is made up of all of the household wastewater that does not come in contact with toilet waste. Gray water carries lower concentrations of the same pathogens as in sewage, also known as BLACK WATER. Just think…laundry water may contain bodily fluids (urine, feces, vomit…) that can transmit disease. Kitchen sink wastewater may carry salmonella from the chicken dinner prepared the night before.

Monterey County Code, Chapter 15.20.120, prohibits any & all gray water from being released above ground. Gray water, with its potential pathogens, must remain connected to your septic system or disposed of in a gray water system permitted by Monterey County Environmental Health.

A. No. Monterey County Code, Chapter 15.20.065 states that construction or major repair of a septic system must be completed by a contractor duly licensed by the California State Contractor’s Board. The following license types may install / repair systems in Monterey County:

  • A – General Engineering
  • B – General Building Contractor

    A general building contractor may not install a septic system unless the contract requires at least two unrelated trades or crafts other than framing or carpentry, or unless the general building contractor holds the appropriate license classification. (Business & Professions Code, Division 3, Chapter 9)
  • C-36 – Plumbing Contractor
  • C-42 – Sanitation System


A. Monterey County code requires a minimum of 100’ linear feet between a water well and a septic tank or conventional leach field. The minimum distance is increased to 150’ between a seepage pit and a water well. Refer to Septic System Site Setbacks for all septic system setbacks.

A. Most septic systems can be designed by a licensed septic contractor or a Registered Environmental Health Specialist. Special circumstances necessitate an engineered system to work around the limiting factor:

  • High groundwater (within 10’ of the bottom of the disposal field)
  • Inadequate soils / Poor percolation rates
  • Bedrock (within 10’ of the bottom of the disposal field)
  • Inadequate area of undisturbed earth available to install a conventional septic system
  • Locally poor ground or surface water quality
  • Areas subject to vehicular traffic
  • Topography or slopes greater than 30%


A. If you have reason to believe your neighbor’s septic system is having problems, contact Environmental Health Review Services at 755-4507. All complaints are kept strictly confidential but you may choose to remain anonymous. A Specialist will visit the site to investigate the validity of the complaint and alert the property owner to a potential problem. If a problem or failure is encountered, the property owner receives a notice of violation that outlines how they must fix the problem.

A. If you can see or smell wastewater, then your plumbing and/or septic system is not functioning properly.

Wastewater backing up into your toilets, sinks, or showers may indicate an household plumbing or a septic system problem. Contact a licensed professional to evaluate your problem as soon as possible. Remember that you must obtain a permit from Environmental Health to make majors repairs to a septic system.

Wastewater on top of the ground constitutes a misdemeanor and should be dealt with swiftly. Contact a licensed septic pumping company to have the septic tank pumped; this will free up capacity inside the tank and stop the wastewater from continuing to bubble up from the ground. Contact a licensed septic contractor to evaluate your septic system and identify the severity of the problem as soon as possible.

A. It is impossible to know the condition of a septic system without an evaluation by a certified septic system inspector who utilizes the proper tools. Ask that a septic system inspection be completed prior to a home sale. Request that the inspector locate all of the system components on a diagram and make an assessment of their condition. The disposal field should be evaluated separately from the tank, often times with a 30-minute water test as an assessment tool. Ask if the previous property owner has the original septic system records; it can save time and money in the event that official records are unavailable.

A. Sometimes, but not if it involves moving the wastewater across a property line. As a general rule, if a structure can support an occupant (living area, kitchen and bathroom) it must have its own septic system.

  • Single Family Dwelling (SFD) = 1 Septic System
  • SFD + Guesthouse = 1 Septic System
    A detached guesthouse is considered a bedroom addition and may share the septic system with the main house.
  • SFD + Caretaker/Senior Unit = 2 Septic Systems
    Caretaker or Senior Citizen units each have a kitchen and are considered individual dwelling units.
  • SFD + SFD = 2 Septic Systems
Commercial facilities may have multiple buildings connected to a single septic system since the septic system is specifically designed to handle the wastewater generated by employees or visitors. Installation of dual disposal fields (2 disposal fields separated by a diversion valve) is required at initial construction for commercial systems


A. Most unincorporated parts of Monterey County are served by individual onsite septic systems. 2-way cleanouts are often installed just outside of the structure and 2’ before the septic tank and can be used to determine if the property is served by a septic system. They normally consist of 4” black or white PVC pipe sticking up out of the ground with a lid secured on top. Another good indicator is a sewer bill; if you haven’t received one in a few months there is a good chance your wastewater goes to an onsite septic system.

A. No. All plumbed structures within 200’ of an approved sanitary sewer line must be connected according to Monterey County Code, Chapter 15.20.040.

A.All septic system repairs must be completed by a licensed septic contractor. The Environmental Health Division should be notified about any and all repairs to determine if a permit is required.

  • Pumping the septic tank does NOT require a permit.


A. All septic permit applications should be dropped off, with a check for the associated fees, to:

Environmental Health Review Services at:
855 E. Laurel Drive, Building H
Salinas, CA 93906

A. See our fee schedule

A. An Environmental Health Specialist (EHS) will contact you within 2 business days of receiving the complete septic permit application to schedule a site visit. Depending on site conditions, the EHS may request soil analysis or a test trench to evaluate how well the ground can accept wastewater. Once the most suitable location on the property is identified for the new septic system, the permit can normally be issued within one day.

If the failing septic system results in a public health threat (for example, wastewater bubbling to the ground’s surface or moving to the neighboring property), contact the Environmental Health Division immediately, 755-4507. The process of obtaining a permit will be accelerated to alleviate the risk to public health.

A. A licensed septic contractor or the property owner may apply for a septic system permit. The property owner must sign the completed application, regardless of who turns it in and pays the associated fee.

A. Ensure that all required setbacks to a septic system are maintained during the installation. For a conventional or standard septic system, the Specialist must observe the following, based on the approved septic system design: Ensure that all required setbacks to a septic system are maintained during the installation. For a conventional or standard septic system, the Specialist must observe the following, based on the approved septic system design:

Septic Tank

  • Brand Name and Capacity of the septic tank (normally visible on tank lid)
  • Effluent Filter installed in the outlet side of the septic tank
  • 2-Way Clean-Outs as directed by Monterey County Code
  • Manhole Risers to ground surface grade if the tank is more than 3’ deep.
Disposal Field
  • Open, drain rock-filled trench with the perforated pipe exposed and a 1½” riser every 50’ that extends down through the rock to the bottom of the trench. This allows the Specialist to measure the effective depth of the disposal field.
If an area must be partially backfilled in order to complete the disposal field, first obtain approval to do so from your Specialist. They will explain how you must install two separate 1½” risers together: 1) extending from the bottom of the trench to the ground surface 2) extending from the perforated pipe to the ground surface. This set of risers must be installed every 50’ for the length of the disposal field. This allows the Specialist to measure the effective depth of the disposal field.
  • Correct Slope of perforated pipe (less than 2% or 2 inches per 100 feet)
  • Distribution Boxes and/or Diversion Valves
  • Distance between each disposal field (minimum 8’ separation or double the effective depth)


A. The price range can vary dramatically depending on the type and size of the septic system required. Contact a licensed septic contractor for estimates.

A. No.

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