Texas Aerobic System Chlorine and Disinfection Requirements

For a Texas aerobic system with surface (spray) application, the effluent must be disinfected before it is sprayed: “Treated effluent must be disinfected before surface application. The effluent quality in the pump tank must meet the minimum required test results specified in §285.91(4)” (30 TAC §285.33(d)(2)(D)).

The acceptable result is in 30 TAC §285.91(4), Table IV: 0.1 mg/l total chlorine residual in the pump tank, or, as the alternative test, fecal coliform not to exceed 200 MPN/100 ml (CFU/100 ml). One of the two is required at each test, at least once every four months.

Tablet chlorinators must use calcium hypochlorite labeled for wastewater disinfection (§285.33(d)(2)(D)); TCEQ warns against pool tablets. New equipment must be listed under ANSI/NSF Standard 46 or approved by TCEQ. The contract must say who maintains the disinfection unit (§285.7(d)(1)(E)), and the report records the device, chlorine supply, and result (§285.90(3), Figure 3).

Summarizes public rules as of Oct 5, 2026; not legal advice; verify with your permitting authority.

What does 30 TAC §285.33(d)(2)(D) require?

The full subparagraph, Effluent disinfection:

“Treated effluent must be disinfected before surface application. The effluent quality in the pump tank must meet the minimum required test results specified in §285.91(4) of this title. All new disinfection equipment shall be listed as approved dispensers or disinfection devices for wastewater systems by NSF International or by an ANSI accredited testing institution under ANSI/NSF Standard 46, or approved by the executive director. After January 1, 2016, all new disinfection equipment shall be listed as disinfection devices for wastewater systems by NSF International or by an ANSI accredited testing institution under ANSI/NSF Standard 46, or approved by the executive director. Installation of disinfection devices on new systems shall be performed by a licensed installer II. Tablet or other dry chlorinators shall use calcium hypochlorite properly labeled for wastewater disinfection. The effectiveness of the disinfection procedure will be established by monitoring either the fecal coliform count or total chlorine residual from representative effluent grab samples as directed in the testing and reporting schedule. The frequency of testing, the type of tests, and the required results are shown in §285.91(4) of this title. Replacement of disinfection devices on existing systems may be considered an emergency repair as described in §285.35 of this title (relating to Emergency Repairs) and shall be performed by either a licensed installer II, a licensed maintenance provider, or a registered maintenance technician.”

The rule is written for surface application systems. For secondary treatment with subsurface disposal, Table IV lists “None” under required tests. Non-standard systems follow the permit.

What result passes, and where is the sample taken?

Item	Requirement	Rule
When disinfection is required	Before surface application of treated effluent	30 TAC §285.33(d)(2)(D)
Test options	Total chlorine residual or fecal coliform, at each required test	30 TAC §285.91(4), Table IV
Passing chlorine result	0.1 mg/l residual in pump tank	30 TAC §285.91(4), Table IV
Passing fecal coliform result	Not to exceed 200 MPN/100 ml (CFU/100 ml)	30 TAC §285.91(4), Table IV
Sampling location	Pump tank; “An unthreaded sampling port shall be provided in the treated effluent line in the pump tank”	30 TAC §285.33(d)(2)(D) and (G)(iv)
Test frequency	At least once every four months (two per year with qualifying electronic monitoring)	30 TAC §285.91(4); §285.7(e)(3)
Tablet chemistry	Calcium hypochlorite labeled for wastewater disinfection	30 TAC §285.33(d)(2)(D)
Equipment listing	ANSI/NSF Standard 46 listing or TCEQ approval for new equipment	30 TAC §285.33(d)(2)(D)
Non-single-family extra tests	One BOD5 and TSS grab per year, each not to exceed 65 mg/l	30 TAC §285.91(4), Table IV

Note the word “or” in Table IV: one of the two tests is required at each visit, not both. Most providers test chlorine residual in the field because fecal coliform needs a lab. The rule sets no retest interval for a failed result; record the failure, the corrective action, and the follow-up result, and check whether the local order requires notice.

Tablet versus liquid chlorination

The rule speaks to “tablet or other dry chlorinators” and requires calcium hypochlorite “properly labeled for wastewater disinfection.” It does not prohibit liquid chlorine feed systems; a liquid system must still be listed under ANSI/NSF Standard 46 or approved by TCEQ if newly installed, and the effluent must meet the Table IV result. The electronic-monitoring option in §285.7(e)(3) requires equipment that “will monitor the amount of disinfection in the system.”

TCEQ’s maintenance page is direct about pool tablets: “DO NOT use swimming pool chlorine tablets in your disinfection system.” It explains that they are made from trichloroisocyanuric acid, dissolve more slowly, “do not thoroughly disinfect the effluent,” carry “a danger of explosion,” and “are not approved by EPA for wastewater effluent disinfection.”

Who is responsible for keeping chlorine in the system?

The rule does not assign it. It requires the contract to “identify who is responsible for maintaining the disinfection unit” (30 TAC §285.7(d)(1)(E)). Whichever party is named, the result still has to meet Table IV at each visit. If the owner supplies tablets and the residual fails, record it on the report with a dated notice to the owner.

What goes on the report?

Figure 3 (30 TAC §285.90(3)) carries three disinfection-related entries: “Disinfection Device” and “Chlorine Supply” in the operational/inoperative checklist, and “Cl2 (Grab)” or “Fecal Coliform” in the tests table with the result in “mg/l, mpn/100 ml, or trace” and the test method. Record the numeric value rather than “pass.” Where a chlorinator was replaced, list it under repairs and components replaced; because §285.33(d)(2)(D) allows the replacement to be treated as an emergency repair, §285.35(c) requires written notice to the permitting authority “within 72 hours after starting the emergency repairs” with “a detailed description of the methods and materials used.”

Sources

• 30 TAC §285.33, Criteria for Effluent Disposal Systems: https://www.law.cornell.edu/regulations/texas/30-Tex-Admin-Code-SS-285-33
• 30 TAC §285.91, Tables (Table IV): https://www.law.cornell.edu/regulations/texas/30-Tex-Admin-Code-SS-285-91
• 30 TAC §285.7, Maintenance Requirements: https://www.law.cornell.edu/regulations/texas/30-Tex-Admin-Code-SS-285-7
• TCEQ, Maintenance of On-Site Sewage Facilities: https://www.tceq.texas.gov/permitting/ossf/ossfmaintenance.html

Last verified: 2026-10-05. Summarizes public rules as of Oct 5, 2026; not legal advice; verify with your permitting authority.

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