Grundfos MQ-3-45 (1HP) On Demand Pump (115V)

This Pump has been Discontinued. See below for the MQ Successor
34.00 LBS
$35.00 (Fixed Shipping Cost)
Standard, Hobbyist

Product Overview

**The Grundfos MQ 3-45 has been DISCONTINUED by the manufacturer. Its replacement is the MQ Successor 3-45, an "on demand" pump that offers slightly higher flow/pressure performance and better functionality. Available in 115V and 220V. It's been 3 years since the MQ 3-45 was discontinued. No one in North America has MQ 3-45 stock left, so save yourself the time of calling or checking around.

1" x 24" Stainless Steel Flex Hose makes connections to existing plumbing easier.  

Video:  How to change plumbing over from a Grundfos MQ 3-45 to a Grundfos MQ Successor 3-45

MQ3-45 On Demand Pump
Complete system The MQ is a complete, all-in-one unit, incorporating pump, motor, diaphragm tank, pressure and flow sensor, controller and non-return valve. The controller ensures that the pump starts automatically when water is consumed and stops automatically when the consumption ceases. In addition, the controller protects the pump in case of faults.

Installation: Due to its compact design, the pump does not take up much space and is easy to install. No space around the pump is required.

Simple operation: The pump features a user-friendly control panel with ON/OFF button and indicator lights for indication of the operational state of the pump.

Self-priming pump: As it is self-priming, the MQ is able to pump water from a level below the pump. Provided it is filled with water, the pump is able to lift water from a depth of 26' in less than 5 minutes. This facilitates installation and start-up of the pump and provides more reliable water supply in installations where there is a risk of dry running and leakages in suction hose or pipes.

Built-in protective functions: If exposed to dry running or excessive temperature, for example in case of seizure or overload, the pump will stop automatically, thus preventing a motor burnout.

Automatic reset: The pump features an automatic reset function. In case of dry running or similar alarm, the pump will stop. Restarting will be attempted every 30 minutes for a period of 24 hours. The reset function can be deactivated. The anti-cycling feature prevents the pump from repeatedly starting and stopping in the event of a dripping tap or a minor leak. If there is no water available, the pump will stop to protect itself and restart automatically when water is available again. 

Low noise level: Thanks to its hydraulic design and internal cooling, the pump is extremely low-noise, which makes it suitable for indoor as well as outdoor use.

Pressure tank: The built-in pressure tank reduces the number of starts and stops in case of leakages in the pipe system, causing less wear on the pump.

Maintenance: No maintenance of the pump is required. Grundfos MQ is built for trouble free operation. It's construction from corrosion resistant materials means it can be used for clean water. 

NOTE: Pump must be placed in area that will not freeze, as this will cause damage to the pump. Placing a pump in an area that is susceptible to freezing, WILL void the Grundfos warranty. 

Warranty: Warranties are not valid on the MQ 3-45 pump when used to boost pressure without a 30 PSI Pressure Regulating Limiting Valve. A 30 PSI Pressure Regulating Limiting Valve must be purchased and installed inline prior to the pump when used in situations where existing inbound water pressure is being boosted. This pump has been known to leak and fail if these steps are not followed when installing and and prior to activating the MQ pump.  

Product Guide - short version
Product Guide - long version
Installation and Operating Instructions

Brochure #2

Grundfos MQ-3-45 Pump Curve
Pumped liquid:    Water
Liquid temperature range:    0 - 95 °F
Range of ambient temperature:    0 - 113 °F
Maximum operating pressure:    108 psi
Pipe connection:    NPT 1"
Electrical data:
Power input - P1:    1150 W
Mains frequency:    60 Hz
Rated voltage:    1 x 110-120 V
Rated current:    10 A
Enclosure class (IEC 34-5):    IP54
Insulation class (IEC 85):    B
Length of cable:    6.56'
Type of cable plug:    NEMA
Net weight:    28.66 lbs
Gross weight:    34.17 lbs

MQ3-45 On Demand Pump

Ideal for boosting from water storage tanks (maximum 30 psi inlet pressure). It is a 1 HP single phase 115V/230V pump with a rated flow of up to 20 GPM at low pressure and a max operating pressure boost of of 60 psi at low flow. With an average performance of 5GPM at 50PSI, it works well in rainwater harvesting applications.

This unit is ideal for pressurizing water from a water storage tank and boosting existing low water pressure. However, in situations where there is inlet water pressure that needs to be boosted by the MQ pump, the water line pressure coming into the pump must be limited to a max of 30 PSI. This can be accomplished by installing a pressure regulating limiting valve prior to the pump. Warranties are not valid on the MQ 3-45 pump when used to boost pressure without a Pressure Regulating Limiting Valve. A Pressure Regulating Limiting Valve must be purchased and installed inline prior to the pump when used in situations where existing inbound water pressure is being boosted. This pump will leak and fail if these steps are not followed when installing and activating the MQ pump.  


  • On-demand (Means when a valve opens and the pressure drops, this pump kicks on automatically)
  • Low noise
  • Auto-reset
  • User friendly control panel
  • Self-priming
  • Built-in, self protect function
  • No maintenance required
  • 2 Year Manufacturer Warranty


  • 1 HP
  • 115V or 230V
  • 1" NPT Connection
  • Liquid temperature range: 32 .. 95 F
  • Rated flow: 20 US gpm
  • Rated head: 91.9 ft
  • Maximum operating pressure: 109 psi
  • Cable length: 6.56'
  • NEMA plug type

NOTE: Max Inlet Pressure = 30 PSI

More Details:

The Grundfos MQ-3-45 is rated as high as 91.9ft of head. This pressure boosting system is a self-priming, multistage, centrifugal pump. It's capable of self-priming from a depth of 26 feet within 5 minutes. Great for pumping potable water and rainwater. Easy to install. If exposed to dry running, excessive temperature, or any overload condition, the pump will stop automatically, preventing a motor burnout. Note: This pump should be used indoors or covered and insulated if used outdoors.