Testing Tap Water at Home

What can a home water test tell you?

A home water test can tell you whether something is present or roughly how much of a common property such as hardness or TDS is in the water, but not whether the water meets health standards. The State Water Board's testing page draws the line plainly: "a lab will be able to provide concentrations of contaminants while a self-test kit will only let you know if a constituent is present."

Your utility already does the heavy testing. LADWP's 2025 report counts more than 100,500 tests covering 240 constituents, and its FAQ says that testing your own tap for everything it tests would cost "well over $3,000." What the supplier cannot see is your own plumbing, which is where a home test or a lab sample earns its keep.

How does a hardness drop test work?

A hardness drop test is a small titration: you measure a water sample into a tube, add an indicator that colors it, then add a second reagent drop by drop until the color changes. The number of drops converts to grains per gallon on the kit's chart, and multiplying by 17.1 gives mg/L as calcium carbonate, the unit water reports use.

The kit linked here, Quality Water Treatment's Pro Products 2403 hardness field test kit (sold by Quality Water Treatment, which shares owners with this site), is listed with three hardness reagents, a test bottle and a measuring tube, at $150 (the shop's listed price in October 2026). Check that a kit's reagents are in date before trusting a reading.

What to expect, from the 2026 reports on 2025 water:

• LADWP Valley neighborhoods: about 6-8 gpg (103-140 mg/L), depending on whether the aqueduct, the local wells or MWD's Jensen plant fed your tap.
• Burbank: about 16.7 gpg (286 mg/L), ranging 148 to 300 mg/L.
• San Fernando: about 11.1 gpg (190 mg/L).
• Glendale: anywhere from about 8.2 gpg on MWD Jensen water to about 20.5 gpg on the city's own groundwater plant water, since Glendale prints no single figure.

A reading far from your supplier's number is worth a second look: a softener, a blend change or a reading error can all explain it. Sizing a softener from your result is covered on softener sizing.

What does a TDS meter measure?

A TDS meter measures how well water conducts electricity and converts that to an estimate of total dissolved solids in mg/L. The USGS explains that pure water barely conducts, while dissolved salts split into charged ions that carry current, so conductivity rises with dissolved minerals.

That makes TDS a mixed bag of everything dissolved: calcium and magnesium, but also sodium, chloride, sulfate and more. It cannot separate hardness from salt, and it says nothing about lead, bacteria or chromium-6. EPA's secondary standards treat 500 mg/L of TDS as a taste and deposits guideline, not a health limit.

Where a meter shines is checking a reverse osmosis unit. Compare the cold tap with the RO faucet: the 2025 reports put TDS at 234-297 mg/L for LADWP's Valley sources, 448 for Burbank and 378 for San Fernando, and a working RO unit certified for TDS reduction should read far lower. Quality Water Treatment lists the Pocket Pal TDS meter (sold by Quality Water Treatment, which shares owners with this site) at $61 (October 2026). More on RO upkeep is on under-sink reverse osmosis.

When do you need a certified lab for testing?

You need a certified lab whenever the question is about health: lead, nitrate, bacteria, arsenic or anything with a legal limit. EPA's lead page says testing "is the only way to confirm if lead is present" and recommends a certified laboratory; LADWP's FAQ puts a typical lead test at around $50.

California accredits drinking water labs through its Environmental Laboratory Accreditation Program (ELAP), and the State Water Board's ELAP page links a map of accredited labs. Ask for a written estimate before sampling, as the Board's testing page suggests.

Lead is the test most Valley homeowners ask about. LADWP reports no lead service lines in its system, including customer-owned lines, so lead at a tap would come from home plumbing such as old solder or brass. In LADWP's 2023 round, the homes sampled were built 1982-1987 with original copper plumbing, chosen because they were expected to have lead solder; the 90th percentile was 3.9 ppb. Lead in Valley tap water has the full numbers.

How do you take a good tap water sample?

Take the sample exactly the way the lab's instructions say, from a faucet you actually drink from. That is EPA's advice on its lead page, and it matters because labs design their bottles and timing around specific rules.

A few habits help any sample:

• Use the lab's bottle. The State Water Board notes that labs supply the sampling bottles.
• Ask about first draw. LADWP's own lead sampling used first-draw samples from home taps, so ask the lab whether it wants the first water out of the faucet.
• Separate supply from plumbing. LADWP suggests comparing the front hose bib with an indoor tap when chasing a taste or odor; a difference points to the house, not the supply.
• Write it down. Note the date, time, faucet and how long the water sat, so a retest can match it.

Under EPA's newer lead rule, utilities sampling homes with lead service lines must test both the first and fifth liter and use the higher result, which shows how much timing can change a lead reading.

Which test should come first?

Start with your supplier's report, then pick the test that answers your actual question. A softener decision needs a hardness reading; a filter check needs a TDS meter or the filter's own test; a lead question needs an ELAP lab.

A sensible order for most Valley homes:

1. Read the 2025 report from LADWP, Burbank, Glendale or San Fernando, published in 2026.
2. Drop-test hardness at a cold tap that bypasses any softener, if you are weighing treatment; see do you need a water softener.
3. Meter TDS before and after an RO unit, if you own one.
4. Send a lab sample for lead if your home has older solder or brass fixtures, or if anyone in the house is especially sensitive to lead.

Skip kits that promise a full lab analysis by mail unless the lab is named and its ELAP accreditation can be checked on the State Water Board's map.