How to Run an SDI Test to ASTM D4189 with a Manual Kit

At a glance. The silt density index shows how quickly feed water will plug a 0.45 µm filter, a good guide to RO fouling risk. The Tech Inc. Manual SDI Test Kit follows ASTM D4189.

How to run the test

1. Flush the line and fit a new 0.45 µm, 47 mm filter.

2. Set the pressure to 2.07 bar (30 psi).

3. Time how long 500 ml takes to pass (t1).

4. Keep flowing for 15 minutes, then time another 500 ml (t2).

5. SDI15 = (1 − t1/t2) × 100 / 15.

Reading the result

• Below 3: good RO feed.

• 3 to 5: improve pretreatment.

• Above 5: high fouling risk.

Frequently asked questions

Manual or online? Use the kit for spot checks and our online analyser for continuous records.

Ask mail@techincresearch.com for kits and filters.