1. NSF/ANSI 58 – 2014 Reverse Osmosis Drinking Water Treatment Systems Sampling systems with storage tanks Mandy Huntoon DWTS Laboratory Group Leader NSF International Joint Committee Issue Paper

2. Influent and product water samples shall be collected and analyzed for all test contaminants following 4 h and 12 h on Day 1 of testing. The storage tank shall be emptied at each sample point. On Days 2 to 4 of testing, 5% of the first day's production rate shall be withdrawn from the storage tank at the beginning of the day and after an elapsed time of 6 and 12 h. A test contaminant sample shall be collected and analyzed from the tank. Days 5 and 6 represent a 54-h stagnation period, under pressure, during which no product water shall be withdrawn. At the start of Day 7, 144 h into the test, a sample shall be collected and analyzed, followed by emptying of the storage tank. A final sample shall be collected and analyzed on Day 7 for the first 4-h period, and the storage tank shall be emptied after each test contaminant sample collection. After the last sample for test contaminants is collected, the storage tank shall be emptied. Sampling systems with storage tanks

3. Variation in sampling Day 1 The storage tank shall be emptied at each sample point. Days 2 to 4 Systems with storage tank and automatic shut-off: 5% of the first day's production rate shall be withdrawn from the storage tank. A test contaminant sample shall be collected and analyzed from the tank. Counter top systems with storage tanks or reservoirs: 5% of the first day's production rate shall be withdrawn from the storage tank from which a test contaminant sample shall be collected and analyzed. Day 7 A sample shall be collected and analyzed, followed by emptying of the storage tank. A final sample shall be collected and analyzed for the first 4-h period, and the storage tank shall be emptied after each test contaminant sample collection.

4. Sampling Options 1.A sample shall be collected and analyzed, followed by emptying of the storage tank. a.Collect the first volume from the system? b.Discard a specified volume, then collect? c.What is the appropriate sample volume size? 2.The storage tank volume is collected in a suitable container and the sample for analysis is collected from that volume.

5. NSF Recommendation Days 1 & 7 The storage tank volume is collected in a suitable container and the sample for analysis is collected from that volume. Days 2-4 5% of the first day's production rate shall be withdrawn from the storage tank from which the test contaminant sample shall be collected and analyzed.