Chemical Descaling Operations
Descaling is a process that removes limescale, calcium, rust and other deposits from equipment and piping to improve function and prevent equipment failure. Multi-unit chemical descale operators are permitted to complete work at temporary descale job sites connected to residential multi-unit properties. To conduct descaling or cleaning at an industrial or commercial facility, see the Utility Piping Systems program page.
Site Type and Permitting
Any descale operation that may discharge wastewater to the sanitary sewer must file a Descale Operator Discharge Permit Application (PDF). The Pretreatment Program must receive the application no fewer than 30 business days before the first descale project begins. If approved, the permit will be issued to the Responsible Corporate Officer and/or Duly Authorized Representative of the descale company and will include an effective date, expiration date and semi-annual reporting requirements.
See the list of currently permitted Multi-Unit Chemical Descale Operations Service Providers (PDF).
Operational Requirements
Advance notification — A permittee must notify the Utility Compliance Services Division of a planned descale project at least 10 business days before operations begin.
Standard operating procedures — A permittee must develop, implement and maintain an up-to-date standard operating procedure (SOP). A copy of the SOP must be kept at each job site.
Cross-connection prohibition — Connection of descale operation piping to the potable water supply is prohibited during circulation of the descale chemistry. A reduced-pressure principle backflow prevention assembly (RPBA) is required for any connection to the potable water supply during flushing and removal of chemistry and associated waste.
Site-specific requirements:
- A permittee must document that all tenants affected by the descale operation have been notified of the operation and its duration. This documentation must be maintained on site and available for review by Utility Compliance Services Division staff.
- A permittee must maintain on site and make available for inspection a copy of the permit and a copy of the required plumbing permit for the site.
- In addition to the permit's pH effluent monitoring requirement, a permittee must collect at least one sample from the affected loop before discharging to the sanitary sewer to confirm pH meets effluent limitations. Results must be recorded and available for review.
Spill prevention — Recirculation of descale chemistries must be monitored to ensure a timely response to potential leaks. A permittee must take all necessary measures to protect the sanitary sewer — including drains, cleanouts and manholes — and the watershed — including retention ponds, storm drains and diversion ditches — from accidental spills.
Waste transportation and storage — A permittee must comply with all applicable local, state and federal regulations for the storage, handling, transportation and disposal of wastes and residues removed for off-site disposal from pretreatment facilities or prohibited from discharge.