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Title 8 — HEALTH AND SANITATION›Chapter 8.56 — SEPTIC TANKS AND SEEPAGE PITS

San Marcos Municipal Code Art. V Specifications

San Marcos Municipal Code · 2026-09 edition · updated 2026-09-30 · San Marcos

Cite as: San Marcos Municipal Code Article V · Text as of 2026-09-30

8.56.300 - Location of Subsurface Disposal Systems.

Any subsurface sewage disposal unit or system or part thereof thereafter constructed or installed in the City shall be so situated that it will be a "safe distance" from any source of water supply as determined by the Director. In determining what is a "safe distance" the Director shall consider the source of possible pollution, the type of soil, surface and subsurface, the type and source of water supply, the geological formation of the ground, the direction of surface drainage, and the depth and direction of ground water flow.

Under no circumstances shall any part of such subsurface sewage disposal unit or system, except the house sewer line, be located closer than 50 feet from any ground water supply.

No part of such subsurface sewage disposal unit or system except that house sewer line, shall be located less than five feet from every building or structure or less than five feet from every property line.

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8.56.310 - Type of Subsurface Disposal System Required.

Any subsurface sewage disposal unit or system hereafter constructed or installed in the City shall consist of a septic tank with effluent discharging into either: (1) a leach field disposal system; or (2) a distribution box connected to a subsurface tile system consisting of at least two lateral absorption lines of approximately equal length, with a maximum variation of ten percent, provided, that with the approval of the Director such distribution box may be connected to a seepage pit or pits, each having at least four feet inside diameter.

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8.56.320 - Minimum Requirements for Septic Tanks.

Any septic tank hereafter constructed or installed in the City, shall meet the following minimum specifications:

(a)

Such tank shall have an inside diameter of at least five feet with a liquid depth of at least four feet. The length of the tank shall not exceed three times the width of such tank.

Such tank shall have a liquid capacity of not less than 1,000 gallons. Such tank shall have at least two compartments, and a manhole with a minimum diameter or width of 22 inches shall be installed in each compartment, over the inlet and outlet pipe.

(b)

The inlet and the outlet of such tank shall each be a vertical four-inch diameter "T" extending such a distance below the liquid level that 40 percent of the liquid depth is below it, and extending a minimum of six inches above the liquid level of the tank. The outlet shall be two inches below the inlet.

(c)

Such tank shall be watertight and shall be constructed of concrete, concrete block, brick or tile. The top of such tank shall be constructed of reinforced concrete at least four inches thick. When such tank is constructed, the walls and bottom of the tank shall be at least six inches thick and shall be adequately reinforced with steel or other approved material. The concrete used for such tanks shall contain one part cement, two parts sharp sand and four parts crushed rock or gravel. Where brick, concrete block, or tile is used in the construction of such tank, the inside shall be plastered with Portland cement mortar composed of one part cement and three parts

sand. The side walls of such tank shall be adequately reinforced with steel or other approved material so as to withstand any inside or outside pressure. The Director may approve alternative materials and construction specifications to meet health requirements.

(d)

The line from such septic tank to the distribution box or leach field shall be constructed of watertight bell and spigot pipe, or such other pipe with watertight joints that the Director may approve.

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8.56.330 - Minimum Requirements for Distribution Box.

Any distribution box hereafter constructed or installed in the City shall meet the following minimum specifications:

(a)

Such distribution box shall be watertight and shall be constructed of the same materials authorized for construction of a septic tank. The inner surface of the distribution box shall have a protective coating of Hunt's Emulsion, or some other protective coating equal thereto in the opinion of the Director.

(b)

The outlets from such distribution box shall have exactly the same elevation and shall be located at least two inches above the bottom of the box. The inlet to such distribution box shall be one inch above the elevation of the outlets.

(c)

Such distribution box shall be connected to a subsurface tile system consisting of at least two lateral absorption lines when approved by the Director.

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8.56.340 - Minimum Requirements for Disposal Lines.

Any subsurface tile system hereafter constructed or installed in the City for the purpose of disposing of the effluent from a septic tank shall meet the following minimum specifications:

(a)

Such tile system shall consist of at least two lateral absorption lines totaling at least 200 feet in length.

(b)

Lateral absorption lines shall be constructed of tile pipe spaced one quarter inch apart so as to provide open joints. The upper one-half of each open joint shall be covered with tar paper or copper screen. Perforated pipe, of materials approved by the Director, may also be used.

(c)

Each lateral absorption line shall be placed in a trench 36 inches deep and 18 inches of rock or gravel grading one to 1-1/2 inch. At least 12 inches of such rock or gravel shall be beneath the bottom of the line, and four inches of such rock and gravel shall be over the top of the line.

(d)

Lateral absorption lines in a serial disposal system shall be level with not more than two inches per 100 feet variation either way.

(e)

Lateral absorption lines shall not be more than 36 inches below the surface of the ground without the prior approval of the Director.

(f)

Every lateral absorption line shall be at least ten feet (center to center) from every other lateral absorption line. All bends used in the disposal field shall have one tight joint to each end of the bend.

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8.56.350 - Substitution of Seepage Pit for Tile System Upon Approval of Director.

A seepage pit or series of seepage pits may be substituted for or used in conjunction with a subsurface tile system, when such substitution or use is approved by the Director, provided, however, no seepage pit shall be permitted where the Director determines that its use might contaminate or pollute an underground water supply.

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8.56.360 - Minimum Requirements for Seepage Pits.

Any seepage pit hereafter constructed or installed in the City shall meet the following minimum specifications:

(a)

Such seepage pit shall be not less than four feet inside diameter and shall be constructed to a depth where the side wall area of the seepage pit will have sufficient porosity to provide adequate drainage as determined by the Director.

(b)

Such seepage pit shall be either rectangular or round. In the case of a rectangular shape, such seepage pit shall be constructed of brick, concrete block, and/or two inch redwood plank securely braced with four- inch by four-inch redwood boards of full thickness with supporting two-inch redwood boards of full thickness with supporting two-inch by three-inch redwood timbers placed every five feet so as to form a securely braced octagon shape.

(c)

The top of such seepage pit shall be covered with a concrete slab or cover constructed of concrete reinforced with steel or other approved material, which slab or cover shall extend not less than 18 inches beyond the outside of the side walls of the seepage pit.

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8.56.370 - Special Approval Required for Systems Serving Multiple Dwellings or…

Ten Persons.

Every applicant for a permit to install or construct a subsurface sewage disposal system or unit to serve residences, institutions or industries, other than a one family residence or a small institution or industry, shall submit to the Director for approval the detailed plans and specifications of the proposed subsurface sewage disposal system. Upon the filing of the required application, accompanied by such detailed plans and specifications, the payment of the fee hereinbefore prescribed and the approval of such plans and specifications by the Director, the Director shall issue a permit for the construction of such subsurface sewage disposal system.

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8.56.380 - Provisions not to be Construed to Prevent the Director From Imposing Additional Requirements.

Nothing contained in this chapter shall be construed to prevent the Director from requiring compliance with higher or more stringent requirements or specifications than those contained herein where compliance with such higher or more stringent requirements or specifications is necessary to maintain a sanitary condition.

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8.56.390 - Provisions Not to be Construed to Prevent the Director From Reducing Requirements.

Nothing contained in this chapter shall be construed to prevent the Director from establishing lower or less stringent requirements or specifications than those contained herein in such cases where a subsurface sewage disposal unit or system may be maintained at such lower or less stringent requirements or specifications in a sanitary condition without detriment to the public health or safety.

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