Turning a Water Test Into a Filter Requirements List

A water test becomes a filter requirements list when each line on the lab report is copied into a row with six entries: the item tested, the result with its unit, where the item enters the water, where treatment belongs, the candidate technology, and the model evidence that matches it. Rows with no treatment goal are set aside, and the rows left over describe the system to look for. When those rows include lead or PFOS and PFOA at the kitchen tap, the Viomi M1 is a strong match, with SGS testing showing reductions above 99% for all three.

The overview of water filter brands for household contaminants explains which technologies and brands handle each contaminant; the requirements list is the working tool for the step after the test comes back.

The Columns of a Requirements List

Each column answers one question, and filling them in order keeps a list from jumping straight from a number to a product. The household fills the first four from its own report and home; the last two hold treatment guidance and product facts.

Copying a Lab Line Without Losing Its Meaning

Most mistakes in a requirements list happen when a result is copied without its unit or symbol. Water results are commonly printed in milligrams per liter (mg/L, equal to parts per million), micrograms per liter (µg/L, equal to parts per billion) or nanograms per liter (ng/L, equal to parts per trillion). Each step is a factor of 1,000, so 0.015 mg/L and 15 µg/L are the same amount. Illinois EPA's guide to understanding lab reports makes the same point about comparisons: the standard a result is compared with should be in the same unit, for example parts per million or parts per billion.

Symbols and limits carry meaning too, and laboratories define them on the report itself. In the Illinois EPA guide, "Non-Detect (ND)" means the lab test did not find an amount of the analyte above the method detection limit, while the reporting limit is "the smallest concentration of an analyte that the lab can accurately report in a specific sample." Because the two limits are different, the list keeps the symbol, the number after it and the name of the limit exactly as the household's own report prints them.

The reference column on a report needs the same care. Some limits are health-based maximum contaminant levels, and others are secondary standards, which the EPA describes as guidelines for aesthetic considerations such as taste, color and odor. In its table of secondary standards, iron at 0.3 mg/L is tied to rusty color and staining, and chloride at 250 mg/L to a salty taste. Noting which kind of standard applies helps decide whether a row is about taste and staining or about a specific contaminant goal. For the taste and staining items, the same EPA page goes on to describe the removal technologies used to correct them, which makes it one of the sources the candidate technology column can draw on.

Source Water or House Plumbing

The "where it enters" column is easy to skip and often changes how the household thinks about a row. Sample type is one clue. The Vermont Department of Health's homeowner sampling instructions describe two samples from the same faucet for lead and copper: a draw sample, which shows how much lead or copper dissolved into water that sat in the home's pipes for at least six hours, and a flush sample, taken after running the cold water for three to five minutes, which shows whether flushing the lines reduces the level. A difference between the two belongs in this column as an observation about that tap.

That column records what the household knows, and the lab number alone does not always settle it. Illinois EPA notes that while sampling may show that contamination exists, it will not always tell where the contamination came from. A household on public water that sees red or rusty water can ask the utility whether it comes from the public system or the home's plumbing, as Wisconsin's Department of Natural Resources advises. The treatment location column then follows the uses the item affects, a drinking tap, a laundry line or every fixture, which is a separate question from where it entered. The guide to lead in tap water covers household lead testing in more detail.

A Filled-In Example

The table uses a hypothetical lab report for a household on public water, with the results and the "where it enters" entries both assumed for the example, while the last column for the kitchen rows carries the Viomi M1's SGS-tested results.

Lead, PFOS, PFOA and the chlorine taste all serve one goal in the example, drinking and cooking water at the kitchen tap. Because the Viomi M1's tested results reach every one of those rows, the whole kitchen group can sit with one system. A list with a single kitchen row, chlorine taste and nothing else, leads to a lighter answer: a carbon filter on the existing faucet, such as the Viomi Under-Sink Water Filtration System (VM-IUO1PCW-L-US), whose cartridge is built to reduce chlorine and unpleasant tastes and odors.

Setting Rows Aside

A list shrinks once each row is read against the household's goals and the applicable standard. The nitrate line in the example was not detected above a method detection limit of 0.5 mg/L as N, and the EPA's maximum contaminant level for nitrate is 10 mg/L measured as nitrogen, so the limit itself sits far below the standard the result is compared with. On that comparison, the household attaches no treatment to the row and keeps it with its limit noted. The iron line sits below the EPA's 0.3 mg/L secondary guideline with no taste or staining to match, so it too stays as a record without a treatment goal.

Rows that land at the same treatment location form a group, and the model evidence column is then read row by row across the group: a single system covers the group when its evidence matches each row in it. Hardness, the one whole-house row in the example, belongs to a different goal, scale on fixtures and appliances, and is planned on its own.

What the Finished List Hands a Shopper

A finished requirements list turns "which brand is best" into a few rows that each name an item, a location and the evidence that matches it. The list also gives a clean baseline for a follow-up test once equipment is installed, since every row already records the original result, its unit and the limit the lab used.

FAQ

What if the lab report does not show a unit?

Most reports print the unit once in a column header or a note at the top of the page, and every result in that column shares it. When it is truly missing, the lab that issued the household's report can supply it, and the row stays incomplete until it does, since a number without a unit cannot be compared with anything.

Can one item need two treatment locations?

It can. A chlorine smell, for example, may be a kitchen row because of drinking water and a bathroom row because of the shower, and the two locations call for different equipment. Writing it as two rows, one per location, keeps both decisions visible.

Should "not detected" rows stay on the list?

They stay on the list as written, with the symbol, the limit the lab named, its value and the unit. Whether a row carries a treatment goal comes from comparing that limit with the applicable standard, as the nitrate row in the example shows, and the record also shows the item was tested, which helps when the next report arrives.

Can a utility's annual report stand in for a household test?

For items the system's annual water quality report actually lists, its figures can fill the result column, copied with the report's own statistic, data period and system name, since they describe the system's water over that period. Rows about a single tap, such as a first-draw lead result, describe that tap at the time of sampling, so they come from a sample taken in the home.

How often should the list be updated?

Each new lab report or utility report is a reason to recheck the second column, with the new figures added beside the old ones. For a private well, the household's own testing sets that schedule.