Can a Phoenix business dilute corrosive waste instead of neutralizing it?

The amendment rewrites IPC 803.1. As Phoenix adopted it, corrosive liquids, spent acids or other harmful chemicals "that destroy or injure a drain, sewer, soil or waste pipe, or create noxious or toxic fumes or interfere with the sewage treatment processes shall not be discharged into the plumbing system without being thoroughly neutralized, or treated by passing through an approved neutralizing device."

Compared with the model text, the city struck these words:

• "diluted," from the list of acceptable treatments,
• "dilution or" from the device description, so the device is a neutralizing device only,
• "diluting water or" from what the device must be supplied with, leaving a "sufficient supply of neutralizing medium so as to make the contents noninjurious before discharge into the drainage system,"
• "automatically" from the device's supply requirement, and
• "or dilution" from the approval sentence, which now reads that the nature of the waste and "the method of its treatment shall be approved prior to installation."

The city's justification is one sentence: "Diluting chemical wastes is prohibited by the Clean Water Act, 40 CFR, 403.6 (d)." The federal rule is narrower than that short city justification: 40 CFR 403.6(d) prohibits an industrial user from diluting a discharge as a substitute for adequate treatment to meet a pretreatment standard or requirement, except where that standard or requirement expressly authorizes it. Phoenix's own plumbing amendment still removes dilution from this corrosive-waste treatment provision. The cost note says the change "requires neutralizing mediums in lieu of dilution." The city marks the amendment as approved in an earlier code cycle, and it is part of the 2024 code that Ordinance G-7397 put in force on August 1, 2025.

• Corrosive waste: a liquid, spent acid or other chemical that damages drain and sewer pipe, gives off toxic or noxious fumes, or interferes with sewage treatment.
• Neutralizing device: equipment that treats the waste with a neutralizing medium before it reaches the building drain, so the discharge is no longer harmful.
• Approved: accepted by the building official. The amendment requires the waste and the treatment method to be approved before installation, not after.

Anyone installing or changing plumbing at a Phoenix facility that drains corrosive waste: laboratories, plating and metal finishing, battery charging rooms, some car wash and cleaning operations, and any process that discharges spent acids. It applies at design and permit stage, so it lands on the designer and the plumbing contractor as much as on the owner.

• A lab remodel adds a sink for spent acid. The design needs an approved neutralizing device on that waste line, with the method and the nature of the waste approved before the device goes in.
• A designer proposes a holding tank fed with extra water to soften the waste. Under the amendment, dilution is no longer an accepted treatment, so the plan needs a neutralizing device instead.
• A small shop only rinses lightly soiled parts. The answer flips: if the wastewater is not corrosive, the section has nothing to require. A shop that is unsure whether its waste counts should ask Planning and Development before it designs the drain.

1. 1List every chemical and process that drains to the building sewer and identify which wastes are corrosive.
2. 2Have the designer specify a neutralizing device and a neutralizing medium for each corrosive waste line.
3. 3Submit the waste description and treatment method with the plumbing plans so they are approved before installation.
4. 4Leave dilution out of the design, including added water meant to bring the discharge within a limit.
5. 5Keep the sewer discharge limits in mind too. City Code 28-8 bars wastewater with a pH under 5.0 or over 10.5, and bars dilution used in place of effective pretreatment, so neutralizing has to bring the discharge inside that range.
6. 6Submit the plans through the city's current SHAPE PHX permitting process and include the waste description and proposed treatment method for review.

• "Thoroughly diluted is fine, the model code says so." Phoenix removed dilution from the text.
• "The device has to be fully automatic." The city struck the word "automatically" from the supply sentence. The device still needs a sufficient supply of neutralizing medium.
• "A plumbing inspection approves the chemistry." The amendment asks for approval of the waste and the method before installation, which is a design-stage step.