Descaling is a process that removes limescale, calcium, rust and etc. 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. Temporary descale job sites under this program are connected to residential multi-unit properties. To conduct descaling or cleaning at an industrial or commercial facility, reference information on the Utility Piping Systems (UPS) program webpage.

Site Type and Permitting

Temporary Multi-Unit Descale Sites 

Any descale operation potentially discharging wastewater into the sanitary sewer must file an Operator Discharge Permit Application (Adobe PDF, MS Word). Required information is listed in the permit application. The Pretreatment Program must receive this application no less than thirty (30) business days before the first descale project commences. If the application for a Descale Operator Discharge Permit is approved, a permit shall be issued to the Responsible Corporate Officer and/or Duly Authorized Representative of the descale company. The permit will have an effective date, an expiration date, and contain semi-annual reporting requirements. 

Please see the list of currently permitted Multi-Unit Chemical Descale Operations Service Providers.

Temporary Multi-Unit Descale Site Operational Requirements

  • Advanced Notification Requirements.

    A permittee shall provide notice to the Special Services Division (SSD) of a planned descale project at least 10 business days prior to the commencement of operations.

  • Standard Operating Procedures.

    A permittee shall develop, implement, and make available for review an up-to-date standard operating procedure (SOP). A copy of the SOP must be maintained at each jobsite.

  • Cross-Connection Prohibited.

    Connection of the piping involved in the descale operation to the potable water supply is prohibited during the circulation of the descale chemistry. A reduced pressure principle backflow prevention assembly (RPBA) is required for any connection to the potable water supply during the flushing and removal of the chemistry and associated waste from the affected piping.

  • Site-Specific Requirements.

    1. A permittee must document that all tenants affected by the descale operation have been notified of the operation and the duration. Documentation demonstrating that tenants have been notified must be maintained on the jobsite and be available for review by SSD personnel.

    2. At each descale site, a permittee must maintain on-site and make available for inspection to SSD personnel a copy of this permit, and a copy of the required plumbing permit for the site.

    3. In addition to the effluent monitoring requirement for pH in the permit, a permittee must also collect at least one sample from the affected loop prior to discharge into the sanitary sewer to ensure that the pH meets the effluent limitations. The results of this pH analysis must be recorded and made available for review by SSD personnel.

  • Spill Prevention.

    Recirculation of descale chemistries in the isolated plumbing being serviced shall be monitored by a permittee to ensure a timely response and the minimization of any adverse impacts from potential leaks.

    A permittee must take all measures necessary to ensure protection of the sanitary sewer (including drains, cleanouts, and/or manholes) and the watershed (including retention ponds, storm drains, and/or diversion ditches) from accidental spills. 

  • Waste Transportation and Storage.

    A permittee must comply with applicable local, state, and federal regulations for the storage, handling, transportation and disposition of wastes and residues removed for off-site disposal from pretreatment facilities and/or prohibited from discharge to the POTW.

Forms & Resources