Code Stories · why the rule exists
Lead-Free Solder, Pipe and Fittings
The rule in Massachusetts today
Not in facts.json. Verbatim, 10.07(1)(a)1.c: "The joints shall be fluxed properly and fastened using lead free solder." 1.e: "Solder filler metals used in the fabrication of solder joints in potable water applications shall be lead free." 3.d: threaded potable joints "shall be made with lead free polytetrafluoroethylene sealant". 4: "Brazing filler metal and brazing fluxes ... shall be lead free."
Why it exists
Lead dissolves into water, especially water that is corrosive or sits in the pipe, and CDC says no safe blood lead level in children has been identified. Even low levels are tied to developmental delays and learning problems that can be permanent. Solder joints, brass fittings and old lead lines are all places where lead touches water. The law shut off the new sources: first solder in 1986, then brass in 2011, when 8% lead was replaced by 0.25% averaged over wetted surfaces. Flint showed the other half of the problem. When treatment stopped controlling corrosion, lead already in the system came out into the tap water.
How it came to be
- Middle Ages — The trade is named after the metal. etymonline.com
- 1986 — Safe Drinking Water Act Amendments of 1986 (Pub. L. 99-339, June 19, 1986) create the first federal lead-free definition. govinfo.gov
- 2011 — Reduction of Lead in Drinking Water Act (Pub. L. 111-380, approved Jan. 4, 2011). govinfo.gov
- 2014 — The new definition takes effect 36 months after enactment (January 2014). govinfo.gov
- 2014-2015 — Flint, Michigan: water source switched without corrosion control, and lead in tap water rises. cdc.gov
- 2020 — EPA final rule implementing the 2011 definition. epa.gov
Make it stick
Mnemonic: 'Point-two for solder, point-two-five for brass.' 0.2% lead in solder and flux; 0.25% weighted average for wetted surfaces. And a true fact to remember it by: 'plumber' comes from plumbum, Latin for lead. The trade was named after the material it now has to keep out.
On the exam
Expect the numeric definitions (0.2% solder and flux; 0.25% weighted average on wetted surfaces), what is exempt (non-potable-only items; toilets, bidets, urinals, fill valves, flushometer valves, tub fillers, shower valves, service saddles, and water-main gate valves 2 in. and larger), and which solders are acceptable on potable lines. MA text (248 CMR 10.07(1)(a)) requires lead free solder and flux on potable copper joints, lead free PTFE sealant on threaded potable joints, and lead free brazing filler and flux. It says 'lead free' without restating the percentages, so the 0.2% and 0.25% figures come from federal law.
What people get wrong
- 'Lead free' means zero lead. It is a legal definition: 0.2% for solder and flux and 0.25% weighted average for wetted surfaces.
- Exempt items mean lead is fine anywhere in a bathroom. The exemption list is specific (for example tub fillers and shower valves). Lavatory and kitchen faucets are not on it.
- Flint was caused by plumbers using lead solder. CDC's MMWR attributes the rise in tap-water lead to the source switch without corrosion control. It was a treatment failure acting on existing plumbing.
Try it: 1 real practice question
Q1. What type of solder is required for potable water supply joints?
Lead leaches from solder into water that stands in the pipes, and it is a neurotoxin that is especially harmful to children. The Safe Drinking Water Act and 248 CMR limit solder and flux on potable lines to 0.2% lead, which bans 50/50 on water supply. Brazing is allowed but is not required on every joint.
248 CMR 10.07These come from the PressureTest bank. Start 7 days free for the full bank, timed exam simulations and drawn isometric problems.