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Two fixed-ratio in-line direct-injection units and a throttling-valve bypass in parallel were investigated for pressure, flow, and chemical discharge transients at measurement sampling intervals of 0.6, 1.0, and 0.6 s, respectively. Flow modulation through each branch of the circuit was hypothesized as a means of varying chemical concentration and applied rates. Test condition factors included flow partitioning through branches, flow rates, in-line unit ratios, chemical sample locations, and pressure dampening with hose length. Flow partitioning through parallel in-line injection units exhibited preferential flow through some in-line units even though units were subjected to equal pressure potentials. Flow rates differed between in-line units up to a factor of 4.58 for two inline units, and up to 10.2 for two units and the bypass. The bypass operating alone had pressure fluctuations up to a CV of 2.6%, and may have been due to the pressure relief valve and/or the throttling valve. Flow and pressure cycles had a frequencies of ~0.3 Hz. However, the bypass tended to dampen flow and pressure fluctuations introduced by in-line units. Single in-line units and dual in-line units usually increased upstream and downstream pressure fluctuations that typically had a frequency of 0.5 Hz. CV in pressure for single units ranged from 1.4 to 18.2%. CV in pressure for dual units ranged from 5.8 to 32.4%. Increased flow rates through in-line units and increased hose lengths downstream from in-line units generally resulted in dampened pressure fluctuations. CV in Br- concentration ranged from 1.3 to 14.5% and metering error ranged from –44 to +57%.