Clean Water Lab
The bottle filter lab is in almost every water unit, and every careful version ends with the same warning: do not drink it. A class can see that the water came out clearer. It has no way to see the germs, the salt or the nitrate still in it. Clean Water Lab runs the same kind of line on a bench, tests the cup on the meters a jar cannot show, and says what the line took to run.
Using this with a class? Make a free class and add your students yourself: each gets a username and password, with no email or Google account needed. Or give them one join code. Using Google Classroom? Post the link there; with a free class, the link also puts each student in your class, so you see their work. mytekDev is also available from the Google Workspace Marketplace, so your school's Google admin can install it for everyone.A first lesson: One period: test the river and guess, settle and filter it until it looks clear, find the germs still in it, kill them, then boil the clear farm well and watch the nitrate go up, and put seawater through a filter, then through reverse osmosis, and read the cost strip.
Set up a free class Share to Google ClassroomWhat a student actually does
A jug of brown river water sits at the left end of a long bench, with a leaf turning in it, and an empty cup waits at the right. The student presses Test the jug: cloudiness 150, germs about 2,000 in a 100 mL sample, salt 300 mg in a liter. Would you drink this? They pick a first move (filter it, boil it, add chlorine, let it settle), then tap stages into the line: Alum and settle, Sand filter. Run sends the water down the pipes, the mud drops out in the tank, a band of dirt shows on top of the sand, and the cup fills clear. Cloudiness 0.3, green. The germ meter is still red: about 6 in 100 mL. Look closer shows a magnified drop with the germs in it. Chlorine turns the last meter green, and the stamp says Safe.
Then the Farm well: clear water that looks perfect, with nitrate at 25 mg in a liter against a limit of 10. Boiling it sends the nitrate up, to 26.3, because some of the water left as steam and the nitrate stayed behind. Seawater goes through the sand and carbon filters with its salt untouched at 35,000 mg in a liter. Only a stage that pulls the water away from the salt fixes it, and each one has a price on the strip under the bench: reverse osmosis takes in 515 L of seawater to make 225 L for 30 people and sends back brine 1.8 times saltier than the sea; a solar still needs 107 square meters of glass.
Eleven sources and 29 stages in all, grouped as Catch it, Kill it, Pull water away from it, Take water from air and Finish it, with floodwater, a delta tube well with arsenic, humid and desert air, coastal fog and the used water on a space station. Eight missions set a source, a number of people and what is on hand (no plug, one gas canister a day, 20 kWh of solar power). Puzzles hand over a mystery jug or a broken line to fix. Make it opens a bench for eleven of the stages, where students build the thing itself from its parts in the real order: a biosand filter, a clay pot, a solar still, the alum jar test, and run its tests.
Make it on the Alum and settle stage runs six jars on the student's own water. On the muddy river 50 mg of alum in a liter settles it from 150 to 10.7 NTU in an hour. Too little leaves specks that never sink, and too much clouds the water again, so the dose has to be found, not guessed.
What they are learning while they work
Nothing here is presented as a lesson. This is what the activity is made of.
| What the student does | What it is |
|---|---|
| Filters the river until it is clear and finds the germ meter still red | Clear is not clean. Germs are far too small to see. Water can look perfect and still carry them, which is why a filter that only makes water clearer does not make it safe. |
| Puts chlorine straight into the muddy river and watches it fail | Order matters in treatment. Mud uses up the chlorine and hides germs from it and from UV light. Real plants clear the water first and disinfect it after. |
| Boils the farm well and sees the nitrate go up | Dissolved is different. Boiling kills germs. It cannot take out what is dissolved, and the water that leaves as steam makes what stays a little stronger. |
| Runs seawater through sand and carbon, then through reverse osmosis | Separating a mixture. Salt in water passes through any filter. Reverse osmosis, a still or a distiller pull the water away from the salt, and the salt has to go somewhere: into the brine. |
| Reads the cost strip and the water budget after each run | Trade-offs and impacts. Every line is sized to the people it serves. One makes a lot of waste water, one needs electricity, one needs a field of glass. The best line depends on what the place has. |
| Tests humid air and desert air before pulling water from them | Water in the air and the dew point. Air holds water as vapor you cannot see. A cold coil only gets it out when it can cool the air below its dew point, so dry air costs far more energy or gives nothing at all. |
| Builds a filter on a Make it bench, runs its tests and fixes what failed | Build, test, improve. The engineering design loop with real materials and steps: sand washed too much lets water rush through untreated, a clay pot dried too fast cracks, a dose too high clouds the water. |
How to tell whether it landed
Ask, and let them show you. A student who has understood it can answer these without help.
- Your cup looked clear and still failed. What did the test find that your eyes could not?
- Why does chlorine work poorly in muddy water?
- Boiling made the farm well's nitrate go up. Why up, and not just the same?
- Where did the salt from the seawater go?
- Reverse osmosis and a solar still both make seawater safe. What does each one cost?
- Why does a machine that pulls water from the air get so little in the desert?
Use it in your subject
Not a technology class? Then the app is how students show what they learned in your unit. More projects for every subject.
Middle school engineering
MS-ETS1-1 to 4, and MS-ETS1-4 most of all: a model that generates data for testing and changing a design. A mission sets the criteria (people served, every meter green) and the constraints (power, fuel, room, supplies), and the strip and the meters are the data. None of the four has a boundary on the numbers shown.
Middle school earth and physical science
MS-ESS3-3, whose clarification names water usage and water pollution, with brine and energy as the impacts to monitor; MS-ESS3-4 on freshwater as a resource. MS-PS1-4 for boiling, the still, the distiller and the cold coil as changes of state of water. MS-ESS2-4 for the still and the air sources as the water cycle in a box, inside its boundary: no quantitative latent heat, so middle school sees energy as comparisons, such as a microwave running 38 minutes.
Grades 4 and 5
5-PS1-1, whose clarification names evaporating salt water: the salt stays behind. Its boundary rules out the atomic-scale mechanism of evaporation, so the grades 4 and 5 level shows faces (Looks, Germs, Salt) and no particles. 3-5-ETS1-1 to 3 for a need, criteria and fair tests of a line.
High school
HS-ETS1-1 to 4: HS-ETS1-4 opens with "Use a computer simulation", and HS-ETS1-3 names cost, safety, reliability and environmental impacts, which is the cost strip. HS-ESS3-1 for access to fresh water and HS-ESS3-4 for refining a solution that reduces impact. The high school level splits the germs into bacteria, viruses, Giardia and Cryptosporidium and shows energy in kWh.
Texas
TEKS §112.7(b)(6)(C) in grade 5, §112.26(b)(6)(B) and (11)(B) in grade 6, §112.27(b)(6)(D) in grade 7, and Environmental Systems §112.50(6)(B) and (10)(D).
Practical notes
- AgesGrades 6 to 8 are the home ground. A grades 4 and 5 level keeps four sources (the river, the farm well, the sea and humid air) and eight stages, with faces instead of numbers. A high school level splits the germ meter into four and gives energy in kWh.
- TimeOne period for the river, the farm well and seawater. A second for the missions, the puzzles, a Make it bench and the sheet.
- EquipmentA computer or Chromebook with a modern browser. Nothing to install. A projector works well for the first test of the river and the vote before it. For the real thing: the bottle filter lab, with the app's build sheet, and nobody drinks what comes out.
- CostFree. The app has no paid tier.
- PrepAbout ten minutes: run the river with Alum and settle and Sand filter, then add Chlorine; boil the farm well; put seawater through Sand filter, Reverse osmosis, Add minerals back and Chlorine and read the strip. Those are the numbers students will see first.
- In a groupOpen Setup in the app's header: which sources and missions students can pick, whether a guess comes before the first test, whether the puzzles are on, and an answer key with a passing line for every mission.
For co-ops, microschools, and classrooms
Set it up once in Setup and hand the project out as the starter; the setup travels with it. Every run is exact, so two students who build the same line from the same source get the same cup and the same strip, and a class can compare lines for the same mission side by side. The sheet asks four questions and puts the line, the cup's test and a picture of the bench on one page to hand in or print.
Common questions
Is it free?
Yes. Clean Water Lab has no paid tier, and it can be tried right on this page without an account.
Does it replace the bottle filter lab?
No. Pair them. Build the real filter first, then run the same kind of line in the app and test the cup on the meters the class could not see. The Bottle filter bench prints a build sheet, and its own tests always end with the same answer to "Is it safe to drink?": no.
How real are the numbers?
The limits are the published ones: nitrate 10 mg in a liter as nitrogen (EPA), arsenic 10 micrograms (WHO and EPA), lead 10 micrograms (WHO, and EPA's action level from late 2027), cloudiness 1 NTU or less so disinfection can work (WHO). What each stage removes comes from the WHO tables of log removal for household and plant treatment, chlorine from EPA's contact-time values and CDC's household guidance, the biosand bench from CAWST's construction manual and the clay pot from Potters for Peace practice. The sources (a muddy river, a farm well, the sea) carry typical values inside the published ranges. They are model values, not a water test of any real place, and a real well needs a real lab test.
Is it safe to drink what students build?
Never. A Safe stamp in the app means every meter in the model is green, nothing more. Every build sheet says not to drink water from a filter built in class, and the app adds a line under the stamp whenever a class-built filter is in the line. Chlorine appears only as grams of chlorine and milligrams in a liter, never as an amount of household bleach.
What does it simplify?
Chlorine works at one temperature and pH (20 °C, pH 7), and its by-products are left out. Chemicals are only the ones a source carries (nitrate, arsenic, iron, lead from old pipes, fuel and oil from floodwater); pesticides and PFAS are not named. Every line is sized to the people it serves rather than limited by its slowest stage. Running is 1 day, 1 week or 1 month, which is enough for a biosand filter to grow its living layer and for mud to clog a membrane, but filters and media never fill up. Look closer shows the cup, or the jug before a run, not any point along the line. The high school settings are fixed: reverse osmosis runs at 59 bar on seawater, and the coil, UV dose and recovery do not change.
Why does boiling make some water worse?
Boiling kills every germ, and the model takes 5% of the water away as steam. Anything dissolved stays in the pot, so it ends up a little stronger: the farm well's nitrate goes from 25 to 26.3 mg in a liter, and the delta well's arsenic from 200 to 210.5 micrograms.
Can it make water from the air?
Yes, three ways, and they show why it is hard. A cold coil uses about 0.28 kWh of electricity for each liter in humid air at 30 °C and 80% humidity, about 2 in the desert by day, and gets nothing on a desert night, when the dew point is under 5 °C. A fog net makes about 5 L for each square meter of mesh a day, only where there is fog, and the water still needs its germs killed. A sorbent harvester runs on the sun with no plug, and needs a lot of powder to do it.
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Where to go next
Start with Clean Water Lab
Trying it costs nothing and takes about five minutes. An account is what makes the work last.
Clean Water Lab is one of the making apps on the platform. Each stage keeps the books, so the water and every dissolved thing that go in come out in the cup, the waste, the steam or the stage itself, and the app's test suite checks that on over a thousand random lines.
Page last reviewed November 2026.
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