poolcntrl
Sign in
← All guides

Walkthrough

How a water test works

Testing your water sounds technical, but it's really just five small steps. Here's the whole thing, start to finish.

  1. 1

    Grab a sample

    Scoop water from elbow-deep, away from the returns and skimmer, where the water is most representative.

  2. 2

    Dip the test

    Dip a test strip (or add the reagent drops) and give it a moment. The pads change color based on what is in your water.

  3. 3

    Read the colors

    Each pad turns a shade that maps to a number — chlorine, pH, alkalinity, and more. Match them against the chart.

  4. 4

    Enter your numbers

    Type the readings into the app (or snap a photo of the strip). No charts to memorize, no math in your head.

  5. 5

    Get your plan

    The chemistry engine reads everything together and tells you exactly what — if anything — to add, and when to retest.

What it looks like done right

Most bad readings are not a bad kit. They are a sample from the wrong spot or a colour read in the wrong light. Here is what each looks like done right.

Taking a sample that represents the pool

Taking a sample that represents the poolHold the cup upside down, push it down to elbow depth, turn it over there and bring it up full, away from the return jets and the skimmer.SkimmerReturn jetNot off the topNot in front of a returnElbow deep,far from the jets
Hold the cup upside down, push it down to elbow depth, turn it over there and bring it up full, away from the return jets and the skimmer.
  • Go elbow deep. Push the cup down mouth first so it fills below the surface, not from the top layer.
  • Stand away from the return jets and the skimmer, ideally on the far side of the pool from them.
  • Test with the pump having run for a while, so the water is mixed.
  • Rinse the cup or vial with pool water before you fill it.

Avoid

  • Do not skim from the surface. The top layer is warmer and carries sunscreen, pollen and debris.
  • Do not fill in front of a return. That water has just come through the equipment, and a tab feeder or salt cell makes it read high.
  • Do not test next to where you just poured something, or before it has had its retest time.

Reading a colour match

Reading a colour matchHold the strip or vial against plain white, in daylight with the sun behind you, and compare it with the chart at the time the instructions give.Daylight,sun behind youPlain white behind itCompare pad to chartat the time on the labelNot undera bulb
Hold the strip or vial against plain white, in daylight with the sun behind you, and compare it with the chart at the time the instructions give.
  • Hold it against something white: a sheet of paper, or the white panel on the kit.
  • Read in daylight, in open shade or with the sun behind you.
  • Read at the time the instructions give. A strip keeps changing colour after that.
  • Hold a strip level while you wait, so the colour from one pad does not run into the next.

Avoid

  • Do not read under a porch light or indoor bulb. Warm light shifts every colour toward yellow.
  • Do not read in direct glare, or with the strip in your own shadow against a dark surface.
  • Do not touch the pads or let the strips get damp in the bottle. Both spoil the colours before you start.

That's it. Testing once or twice a week takes a couple of minutes and is the single habit that keeps a pool easy. Got readings in front of you? Run them through the free calculator — it's the same server-side chemistry engine the app uses, and it tells you the product and the amount for your pool's gallons. Free, no account, no limit. The app adds the part a calculator can't: it remembers your numbers, so you see trends instead of just today's snapshot.

Basics 1 of 6 · Test

Next: What each measurement means →

Keep learning

How to add chemicalsThe safe, simple sequence for adding anything to your pool — animated step by step.Cloudy, green and what to do about itWhy pools go cloudy or green, what really clears them, clarifier versus flocculant, and how to read a pool store’s printout.What each measurement meansPlain-language explanations of every reading — what it measures and why it matters.What each chemical doesWhat every product does, how it’s added, and why the method matters.Choosing your chemicalsLiquid or powder, tabs or a salt cell, drops or strips — the real options for each job and the honest trade-offs of each.After you add chemicalsThe safety and comfort steps that follow any addition — and the reasoning behind them.Types of poolsPlaster, fiberglass, vinyl, tile, chlorine, saltwater — how each changes your routine.Pool equipment explainedPumps, filters, chlorinators, heaters, timers — what each part does for you.Closing & opening your poolThe two guided checklists that bookend the season — each step with its why.Protecting your pool from a freezeWhat to do when a freeze is forecast — four steps, ranked by the damage each one prevents.Draining part of your poolWhen a plan says to replace water: a quarter at a time, where the water can go, and when to stop and call a pro.How long to run the pump after you add somethingWhy the pump goes on before you pour, how long it stays on, and why the retest waits.Kids, pets and pool chemicalsStoring chemicals out of reach, keeping acid and chlorine apart, and who stays out of the water until the retest.Coming back to a pool after months awayA pool nobody has tested in months: what to check, in what order, before you add anything.Storms, heavy rain and pollenWhat to do before and after a storm, why the chemistry waits for a test, and how to tell pollen from mustard algae.Brown water, metals and stainsWhy well water browns after a shock, how to tell metal from algae, what a sequestrant does, and the vitamin C stain test.Where our numbers come fromThe methodology behind every target and dose — the ratios, the caps, the rounding, and why AI reads but chemistry decides.