GPM to L/s Converter

International pump specifications, chemical dosing systems, and process fluid controls where metric flow rates are expressed in L/s.

Common in water treatment and chemical injection systems.

Municipal water treatment plants in most countries outside the US rate their pumps and clarifiers in L/s — a typical 1 MGD (million gallons per day) plant produces 43.8 L/s on average but has instantaneous pump flows closer to 80–120 L/s during high-demand hours.

European EN 12255-6 wastewater treatment standards specify aeration tank air flow and recirculation pump flow exclusively in L/s or m³/h, making this conversion essential when integrating American-supplied skids into EU plants.

Chemical dosing pumps for chlorine, polymer flocculant, or coagulant injection are universally rated in L/h or mL/s in their metric datasheets, but their feeders often need to be matched to a process flow expressed in GPM — a 500 GPM raw water line receiving 2 mg/L chlorine demand needs a dosing pump of about 0.4 mL/s (1.4 L/h) of 12.5% sodium hypochlorite.

Fire protection engineers using NFPA standards (which are in GPM) collaborating with European colleagues using EN 12845 (in L/s) will run this conversion constantly: a sprinkler demand of 250 GPM equals 15.8 L/s, and a fire pump rated 750 GPM (a common size) equals 47.3 L/s.

In pharmaceutical water systems, USP purified water and WFI loops are designed around L/s or L/min flow rates per the ASME BPE standard, while legacy plant documentation in the US may have been recorded in GPM — converting and reconciling these records is a routine task during plant upgrades and FDA inspection prep.

Cooling tower make-up water systems often specify bleed-off and evaporation rates in L/s in OEM literature (BAC, EVAPCO, Hamon) while plant P&IDs developed by American EPCs use GPM, requiring this conversion at the equipment specification boundary.