Styrene in Well Water: The Public 0.1 mg/L Line

By SubcontractorHub Editorial Team·Published October 2026

A solvent panel can list several organic names on one page. The digit next to styrene is not the digit next to total xylenes, and it is not the digit next to dichloromethane. Dealers who sell treatment still have to say which public line they are reading. SubcontractorHub is software for the customer record. This page is the row. It is not a treatment design.

The Public 0.1 mg/L Line for Styrene in Well Water

The national primary drinking water regulations are legally enforceable primary standards and treatment techniques that apply to public water systems. In the organic block, styrene shows an MCLG of 0.1 and an MCL of 0.1. The potential health effects cell says liver, kidney, or circulatory system problems. The source cell says discharge from rubber and plastic factories and leaching from landfills.

Footnote 2 says units are in milligrams per liter unless otherwise noted, and that milligrams per liter are equivalent to parts per million. 0.1 mg/L is therefore 0.1 ppm on that note. It is not a second standard hiding under a different name. Moving the same digits to micrograms per liter uses the 1,000-to-1 scale on milligrams and micrograms. 0.1 mg/L is 100 µg/L on that scale. Write both labels if the lab used the smaller unit, so a later reader does not think 100 is a new limit.

An MCLG is a goal. An MCL is the enforceable public number. On this row the two cells print the same digit. That match is not true of every neighbor. The definitions of those two words are on MCL and MCLG. A goal is not a fine, and a matching pair is still one line.

The 0.1 mg/L Figure in the Organic Table

Section 141.61, as printed on the Cornell eCFR page fetched the same day, lists maximum contaminant levels for volatile organic contaminants. Styrene, CAS 100-42-5, is item (14), at 0.1 mg/L. Xylenes (total), later on that table, are 10 mg/L. Those are not one number. The xylenes row has its own page, xylenes in well water.

Paragraph (a) says those volatile-organic levels apply to community and non-transient, non-community water systems. A private well is not named in that sentence. A dealer who copies the 0.1 mg/L line onto a kitchen-tap jug still has to say the jug is not the public-system rule. The difference between a city system and a private well is what is a public water system.

Styrene in Well Water Is Not the 10 mg/L Row

Total xylenes print 10 mg/L on the same national table, with a source cell that names petroleum factories and chemical factories. That is a different chemical and a different source sentence. Ethylbenzene prints 0.7 mg/L, on ethylbenzene in well water. Toluene prints 1 mg/L, on toluene in well water. Do not paste a petroleum-factory sentence onto the styrene row because the words sound related.

Chlorobenzene on the national table is also 0.1 mg/L, with a source cell that says chemical and agricultural chemical factories. The matching digit is not a reason to merge the rows. Dichloromethane is 0.005 mg/L, on dichloromethane in well water. Adding the neighbors together is not the rule this page fetched. If the lab wrote styrene, write styrene.

What the Note Holds, and What It Does Not

The table above is the note. It is not a quote, and it is not a removal design. A customer who wants a price still needs a test, a model, and a scope. Those live on the job. This page only stops the wrong digit from landing in the scope.

What the BAT Marks Do Not Promise

Table 2 marks granular activated carbon and packed tower aeration for styrene, CAS 100-42-5. The oxidation column is empty. Those marks identify a technology the rule names for compliance with the MCL. They do not say what percent a cartridge in a basement will remove, and they do not say the empty oxidation cell is a ban you can explain as a product feature.

A city plant and a point-of-entry tank are not the same machine. If you sell carbon, say you sell carbon. Do not say the X in the GAC column is a guarantee on this well. No removal percentage was fetched for this row, so none is printed here. Dichloromethane, on the same technology table, marks packed tower aeration and leaves granular activated carbon empty. That difference is another reason not to copy one solvent's marks onto the other.

What Should the Styrene in Well Water Note Say?

Five lines keep the next visit from borrowing a neighbor. If a line does not apply, mark it skipped. A blank line looks the same as a step you forgot.

1. The chemical name as the lab printed it, plus CAS 100-42-5 if the sheet has a CAS column.
2. The result and the unit. If the unit is µg/L, show the mg/L equivalent on the 1,000 scale before anyone compares it with 0.1.
3. The public pair you compared it with: MCLG 0.1 mg/L and MCL 0.1 mg/L, named as the national table.
4. Whether the sample is a private well or a public system. Paragraph (a) names community and non-transient, non-community systems.
5. What you did not claim: no removal percent, no installed price, and no statement that 0.1 mg/L is xylenes' 10 mg/L.

Where the Row Sits on the Job

The lab sheet belongs with the customer, the address, and the date of the sample. A price for equipment is a later page, after someone has read this row and the rows next to it. Mixing the 0.1 mg/L line into a softener quote because the water “smells like solvent” skips the chemical name.

How a dealer reads a full panel, including which tests were actually run, is the well water testing guide. The software that holds the customer file is water treatment contractor software. This article does not size a filter and does not tell a household the water is safe to drink.

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