You do not have to use a special bottle for this screening. Any small clean jar will work—8 ounces of water is enough.
Samples must be less than 48 hours old for a valid nitrate result.
Pick a tap that supplies water that has not run through any treatment devices (water softener, carbon filter, etc.). An outdoor faucet often works well.
Disconnect any hoses before collecting the sample; do not sample through a hose. Run the water for several minutes before collecting the sample. Rinse the sample bottle and lid thoroughly in the water to be tested; then fill and cap the bottle.