Grundfos Hydro Multi-B Duplex Constant Pressure Booster - CME Pumps

Hydro Multi-B Duplex is a factory-built constant-pressure booster with two Grundfos CME horizontal multistage pumps piped in parallel on a common base frame, with stainless steel inlet and outlet manifolds, isolating and check valves on every pump, pressure gauges, outlet-pressure sensors, a breaker cabinet, and a 3 to 5 psi pressure switch on the suction manifold for dry-running protection. It arrives pre-piped, pre-wired and factory-tested.

Each CME pump carries its own integrated variable-speed drive, and the system holds one outlet pressure by varying speed and cutting pumps in and out as demand changes, alternating duty so run hours even out. The horizontal CME layout keeps the whole system at about 41 in tall, which suits mechanical rooms with low ceilings or overhead piping.

Up to 318 GPM and 243 ft of head across the duplex builds listed here, for apartment buildings, hotels, schools, offices and light commercial and process boosting. CME pumps are within the DOE test standard but are not yet regulated, so they carry no PEI rating.

Grundfos documents its CME booster systems in the Hydro Multi-E data booklet, which is the source for the curves, dimensions and limits on this page. Standard hydraulics expect a flooded or pressurized inlet, and the system is rated for indoor installation only.

Hydro Multi-B ships as a factory-built duplex or triplex, chosen at purchase. Each added pump adds flow at the same pressure, and the system cascades pumps in and out on demand. The triplex version is listed separately: Hydro Multi-B Triplex.

More pumps hold more pressure at the flow the building actually draws. Each pump carries a share of the water, so each sits higher on its own curve: at 200 GPM a CME 15-1 system adds 63 ft (27 psi) on two pumps and 78 ft (33 psi) on three. The shut-off pressure at zero flow is the one figure that does not rise, because it is set by the pump build.

Figures read from the Grundfos CME 15 curve chart, Data Booklet 99347082, printed page 41.

Max boost is the peak of the curve near zero flow, a ceiling rather than a working point; max flow is the end of the duplex curve; both read from the Grundfos CME curve charts (Data Booklet pages 38 to 42). Part numbers from the Grundfos price list effective January 1, 2026; motor HP and connections from the Data Booklet. Other builds are available on request.

Voltage is fixed per part number. Confirm the service before ordering.

From the Grundfos dimensional drawing for CME systems: A1 is overall height to the top of the breaker cabinet, B length, C depth. Dimensions may vary by plus or minus 0.5 in. Grundfos asks for 3 ft of clearance on all sides. Source: Data Booklet 99347082, printed pages 47 to 48.

Sources: Grundfos price list effective January 1, 2026 (part numbers, HP, dry-run switch); Data Booklet 99347082 (10.2025) pages 4 and 10 to 13; Hydro Multi-E brochure (11.2025) for approvals.

Maximum feeder overcurrent protective device rating for the whole system, as printed by Grundfos for Hydro Multi-E. Supply tolerance plus or minus 10%. Motors of 5 to 7.5 HP need an especially reliable earth connection because leakage current exceeds 3.5 mA. Source: Installation and Operating Instructions 98419766, page 28.

A pump curve plots what the system adds to whatever pressure arrives at the inlet — never the discharge pressure and never the setpoint. Each cell reads feet of head added (psi added). The one-pump row is what the system delivers at low demand, before the next pump cuts in.

CME 3 builds — flow in US GPM across the top

CME 5 builds — flow in US GPM across the top

CME 10 builds — flow in US GPM across the top

CME 15 builds — flow in US GPM across the top

CME 25 builds — flow in US GPM across the top

Drawing from a tank, cistern or well — nothing arrives with pressure, so what the system adds is what you get. Read the table straight through: a duplex CME 15-2 at 120 GPM comes out at 159 ft (68 psi).

Fed by a city main — the system adds on top of what already arrives, and the controller holds the total at the setpoint. With 108 psi wanted at the outlet on a 40 psi main, the duplex CME 15-2 only has to add 68 psi and delivers about 120 GPM; with 104 psi wanted, it adds 64 psi and delivers about 160 GPM. Incoming pressure buys you more flow, not more pressure — and inlet pressure plus the closed-valve pressure must stay under the 145 psi system rating.

Ask the system for more than it can deliver at your setpoint and all pumps run at full speed continuously, which is where motors and seals wear out. Grundfos also sets a floor: do not run below 10% of one pump's rated flow. Sizing to the building rather than to the headline maximums is what makes it last. Send us the peak flow, the setpoint and the inlet pressure and we will return the build with the manufacturer's curve for it.

Grundfos publishes these systems' performance as curve charts, not tables. The figures above are read from those charts (Data Booklet 99347082, 10.2025, printed pages 38 to 42; the charts are also in the image gallery), heads rounded down to the whole foot and psi = ft x 0.433 rounded down; a blank cell means Grundfos does not draw that curve at that flow. The first column is the ceiling at or near zero flow, not a working point. Curves are at a fixed 3,480 rpm, 60 Hz, airless water at 68 °F, ISO 9906:2012 Grade 3B; fitting and valve losses are not included. Grundfos does not publish a best operating range for these systems. Hydro Multi-B is listed by Grundfos at 208-230V and 460V; the charts are drawn at 60 Hz for the CME pump builds.

Source: Data Booklet 99347082, printed page 13.

CIM modules fit in the pump terminal box and must be fitted by authorized persons. Tank sizes from the Grundfos price list effective January 1, 2026 (recommended minimum sizes); CIM part numbers from Data Booklet 99347082, printed page 53.

The system is set up and run from the operating panel on the master pump, with no app required. Grundfos GO adds guided commissioning, live operating data, alarm troubleshooting and PDF reports on a smartphone. Grundfos lists the MI 301 mobile interface as the accessory for this: it pairs with the phone by Bluetooth and reaches the pumps by radio or infrared. It is sold separately.