Each group needs:

• 8 paper cups, to hold test samples of deionized water, purified water, school tap water, salt-water solution, and each student's sample of tap water brought from home
• ~400 ml deionized water (200 ml for test sample, 200 ml to make salt-water solution), such as chemical grade, 1 gallon bottle (CAS 7732-18-5) at http://www.sciencecompany.com/Deionized-Water-1-gal-P16280.aspx; some company and university research labs are willing to give teachers some deionized water for free
• ~200 ml purified water, such as 1 gallon bottle at grocery stores or Walmart
• ~200 ml school tap water
• ~2g salt and 200 ml deionized water (purified water works, too)
• ~200 ml sample tap water from home, per student
• LED-conductivity tester, such as the one in Figure 1-left, made by the teacher from 2 AA batteries in a battery holder with switch, breadboard and LED light, wire, alligator clips and electrical tape, mounted on sturdy cardboard; connect everything as shown on the Testing Equipment Setup Visual Aid (which also provides website sources for example materials)
• electrical conductivity meter, see Figure 1-middle, such as HM Digital AP-2 AquaPro Water Quality Electrical Conductivity Tester at https://www.amazon.com/HM-Digital-AP-2-Electrical-Conductivity/dp/B0038QTQZ8/ref=sr_1_3?ie=UTF8&qid=1392051994&sr=8-3&keywords=conductivity+tester
• multimeter (includes two test probes), see Figure 1-right
• a map of your local school district divided into ~5 distinct areas; see the Procedure section for details
• extra 200 ml purified water in cups or squirt bottles, for rinsing testing equipment between samples
• paper towels, for drying rinsed testing equipment
• Should I Drink That? Worksheet, one per person
• Lab Equipment Testing Instructions, one per group
• (optional) tray to hold the water samples in cups, to contain any spillage
• (optional) calculators, for calculating averages

To share with the entire class:

• sink and drain, for source of school tap water and disposal of water samples
• marker or tape and pen, for labeling cups to identify water samples
• (optional) capability to show students a four-minute online video