New Water Main Disinfection and Test Water Discharge: How to Coordinate AWWA Standards with TCEQ Rules

What do TCEQ and AWWA each require for a new main?

TCEQ makes the AWWA standards mandatory for public water systems. Under 30 TAC §290.44, distribution mains must be built to current AWWA standards (subsection (a)), and sanitary precautions, flushing, disinfection and sampling must follow AWWA's standards for disinfecting water mains (subsection (f)).

The specific requirements in §290.44 are:

• new mains are thoroughly disinfected under AWWA Standard C651, then flushed and sampled before service (§290.44(f)(3));
• microbiological samples check the disinfection, and sampling is repeated if contamination persists (§290.44(f)(3));
• at least one sample for each 1,000 feet of completed line, or at the next sampling point beyond 1,000 feet the design engineer designates (§290.44(f)(3));
• the hydrostatic leakage rate may not exceed what AWWA formulas allow (§290.44(a)(5)).

C651 itself sets the chlorination methods, doses and contact times. Read the edition your utility and specs reference. Those details belong in the water and sewer utility design package, not in a field memo.

Where do the two rule sets pull against each other?

Disinfection wants strong chlorine in the pipe, and the discharge rule wants almost none leaving the site. The water that just did its job inside the main is the water that cannot go to a creek as it is.

TCEQ's hydrostatic test water general permit, TXG670000, defines hyperchlorinated water as potable lines treated with chlorine for disinfection and then flushed. For new vessels and potable water vessels, hyperchlorinated water discharged to water in the state is limited to 0.10 mg/L total residual chlorine, daily maximum (Part III, Section A.1).

That gap is the whole coordination problem. A plan written by the disinfection crew alone tends to stop at "flush the main." A plan written by the discharge side alone tends to assume test-strength water. Neither matches what the pipe actually releases.

How should disinfection, pressure testing and flushing be sequenced?

Write the sequence down, then attach a discharge plan to each step that releases water. Projects order these steps differently, set by the specs and the utility. What matters is that each release has a known quality and a known route.

1. Fill and pressure test, holding leakage within the AWWA allowance.
2. Chlorinate per C651 and hold for the contact time.
3. Flush the heavily chlorinated water, dechlorinating before release.
4. Collect bacteriological samples at the required spacing.
5. If samples fail, redisinfect and repeat steps 3 and 4.

Each release gets its own residual chlorine and pH reading. Do not assume the pressure test water and the disinfection flush carry the same chlorine. Where the water lands, protect the ground too; see erosion and sedimentation control at the discharge point.

Which discharge rules apply to the flush water?

Hyperchlorinated flush water goes under TXG670000; ordinary flushings can ride on the construction permit. The Construction General Permit lets a covered site discharge potable waterline flushings, but excludes hyperchlorinated water unless it is first dechlorinated and is not expected to harm aquatic life (TXR150000, Part II, Section A.3).

Under TXG670000, a new potable water main needs no NOI (Part II, Section C.4), but the conditions apply in full:

• sample in the first hour, and again from the last 10% if the release runs past an hour, after treatment and before the water mixes with stormwater (Part III, Section A.1);
• control the rate to prevent flooding and erosion, onto a splash pad or other protected surface (Part III, Section B.1);
• add no chemicals to the main except chlorine or tracer dyes (Part III, Section B.5);
• give 48 hours' written notice to the TCEQ regional office, and to the MS4 operator if the release starts inside one (Part III, Sections B.13 and B.14).

Dechlorination happens outside the main, after the water leaves it. AWWA publishes a separate field procedure for it, AWWA C655, Field Dechlorination, whose scope covers flushing and pipeline disinfection discharges. Our post on chlorine neutralization before discharge covers the field side.

What if the bacteriological samples fail?

Plan for a second round before you need it. §290.44(f)(3) requires sampling to be repeated if contamination persists, and in practice that means redisinfecting and flushing again. The discharge plan has to run twice: chemical supply, erosion controls and the discharge point all have to be ready again.

TXG670000 waives new analyses for a vessel that fails its hydrostatic test and is retested within 30 days, if the first discharge had no exceedances and no pollutants were added (Part III, Section A.3). A redisinfection adds new chlorine, so plan to sample the second flush as its own discharge.

How do you keep the two sets of records straight?

Keep the utility acceptance record and the discharge record apart. Bacteriological results answer the water utility and §290.44. Residual chlorine and pH results answer TXG670000.

TXG670000 asks for the date, time and place of each sample, who took it, the laboratory and method, and the results (Part IV.7.h), kept for three years (Part IV.9). Label each sample by purpose in one log, and either reviewer finds the answer quickly.

Limits of this article: this is general education on 30 TAC §290.44, TXR150000 and TXG670000 as of October 2026. It does not restate AWWA C651 or C655, which you should read in the edition your contract names. Utilities and cities add their own acceptance and discharge terms.

Frequently asked questions

Does Texas require AWWA C651 for new water mains?

Yes. 30 TAC §290.44(f)(3) requires new mains to be thoroughly disinfected in accordance with AWWA Standard C651, then flushed and sampled before service.

How many bacteriological samples does a new main need in Texas?

At least one for each 1,000 feet of completed waterline, or at the next sampling point beyond 1,000 feet that the design engineer designates, under §290.44(f)(3). Your utility may ask for more.

Can the pressure test and the disinfection flush share one discharge point?

Often, yes, if the controls fit the worse of the two releases. Test each release on its own, because their chlorine and sediment can differ.

I'm the engineer of record on a new 8-inch line in a Texas MUD, and the utility's acceptance spec and our SWPPP were written by different people. What should I check first?

Check that the specs name who dechlorinates, the 0.10 mg/L target, where the flush goes, who sends the two 48-hour notices, and what happens if bacteriological samples fail. Then make the SWPPP's non-stormwater section match.

I'm a utility contractor and our first bacteriological samples failed on a new main. Do I need to tell TCEQ before the second flush?

The 48-hour written notice to the TCEQ regional office applies before initiating a discharge (Part III, Section B.13). Treat the second flush as a new discharge, give notice, and sample it.

Related resources

• Hydrostatic Test Water: What Texas Developers and Contractors Need to Know Before Discharge
• Hydrostatic Testing Records and the TCEQ Audit Trail: What Contractors Need Before an Inspector Shows Up
• Hydrostatic Testing on Elevated Storage Tanks vs. Buried Pipelines: Why They Need Different Compliance Plans
• Discharging to a Storm Drain vs. Sanitary Sewer: Why Texas Contractors Get It Wrong on Pipeline and Tank Projects

Getting a new water main disinfected, accepted and discharged without a hitch?

We put disinfection, testing, flushing and discharge into one sequence in the plans and specs, so the utility and the discharge rules both get what they need.

We specialize in:

• Water and sewer utility design
• Specifications for disinfection, flushing and dechlorination
• Hydrostatic test water discharge planning
• Construction administration for Texas land development
• SWPPPs and erosion and sediment control plans
• Coordination with water utilities and MUDs

Modern Engineering Solutions, McKinney, Texas. Contact: (214) 833-6748 or mod-eng.com