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NYC cooling towers · 24 RCNY §8-04(f)

Summer hyperhalogenation and its declaration

Each summer, in the warm weather when Legionella grows fastest, every cooling tower that holds water gets a biocide treatment called hyperhalogenation between July 1 and August 31. A Legionella sample follows 3 to 31 days later, and the owner declares the treatment to DOHMH within 30 days.

Check a building freeLast verified Oct 14, 2026

What it asks

What the owner has to do

  1. Treat between July 1 and August 31At least 5 ppm free halogen held for at least 6 hours, measured at two points, through the whole system including standby equipment.24 RCNY §8-04(f)
  2. A certified applicator and a registered productThe work is done or supervised by a New York State 7G applicator, with a biocide registered with NYSDEC.24 RCNY §8-04(f), §8-05(c)
  3. Sample 3 to 31 days afterA Legionella culture after the treatment, read against Table 8-1.24 RCNY §8-04(f)(4)
  4. Declare it within 30 daysThe DOHMH form CT-SH-DF01, uploaded through the portal and signed under penalty of perjury.24 RCNY §8-04(f)(5)
  5. The only exemptionA system drained and shut down for the whole window does not need the treatment.24 RCNY §8-04(f)

Deadlines

The clocks

  • HyperhalogenationJuly 1 to August 3124 RCNY §8-04(f)
  • Legionella sample after the treatment3 to 31 days after it24 RCNY §8-04(f)(4)
  • Declaration CT-SH-DF01Within 30 days of the treatment24 RCNY §8-04(f)(5)

Penalties

What a violation costs

First violation / repeat, per the penalty schedule, with DOHMH’s violation code where it has one. Since May 8, 2026 there is no cure period at inspection.

  • Legionella sample 3 to 31 days after hyperhalogenation24 RCNY §8-04(f)(4)$2,000 / $4,000 · AH8S
  • Declaration of summertime hyperhalogenation within 30 days24 RCNY §8-04(f)(5)$1,000 / $2,000

FAQ

Questions owners ask

What does the declaration record?

The applicator and their 7G certification number, the protocol, the pump start and end times, the product and its NYSDEC number, and the pH and free halogen readings at two points.

Does a tower that ran only part of the summer need it?

Yes, unless it was drained for the whole July 1 to August 31 window.

Is a corrective hyperhalogenation the same thing?

No. A hyperhalogenation after a high Legionella result is a separate corrective action and does not replace the summer treatment.

Your building

See the clock DOHMH sees

Type the address. The free check shows the last sample date DOHMH has, the days left on the 31-day clock, the inspections and any OATH summons on the lot.

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Sources · Last verified Oct 14, 2026

A plain-English summary of the rules, not legal advice. The rule text and DOHMH’s guidance decide; check them before you act.