Please find the link for the following US EPA method

Method 1602 describes the single agar layer (SAL) procedure.

Summary - A 100-mL ground water sample is assayed by adding MgCl2 (magnesium chloride), log-phase host bacteria (E. coli Famp for F+ coliphage and E. coli CN-13 for somatic coliphage), and 100 mL of double-strength molten tryptic soy agar to the sample. The sample is thoroughly mixed and the total volume is poured into 5 to 10 plates (dependent on plate size). After an overnight incubation, circular lysis zones (plaques) are counted and summed for all plates from a single sample. The quantity of coliphage in a sample is expressed as plaque forming units (PFU) / 100 mL. For quality control purposes, both a coliphagepositive reagent water sample (OPR) and a negative reagent water sample (method blank) are analyzed for each type of coliphage with each sample batch.

http://www.epa.gov/nerlcwww/1602ap01.pdf