The best wastewater pump station monitoring solution for up to 4 pumps.

    Constant speed pumps

    • Uses the most advanced volumetric flow algorithm ever patented to calculate the flow in and out of lift stations with 99% accuracy.
    • Calculates the capacity and efficiency (Gallons/Watt) of each pump.
    • Real Time influent flow (analog level sensor required). Real Time flow is calculated every 30 seconds or when the level rises or falls of 3 inches, whatever comes first.
    • 4-20mA analog output proportional to flow.
    • Detects abnormal pump capacity, efficiency, run time, stop time and sequence of operation and generate alarms on the display and remotely. The free MaidMaps Scada software (or users software) required for remote monitoring.
    • Easy installation: connect one current clamp per pump and optional analog level sensor (for real time flow).
    • If no analog level input is available, flow will be calculated at each pump cycle.
    • Optional Maid Labs MerMaid lift station analysis software compatibility.

    Variable speed pumps

    • The Volucalc RT integrates up to 4 pump curves with multiple RPM for each to derive pumped flow and calculate inflow rate.
    • Uses calibrated pump curves, level and force main pressure to extract the pumps’ flow rate and adjust its 4-20mA analog output proportionally.
    • In lift stations with 3 pumps or less, Volucalc RT uses the pumps’ efficiency to detect abnormal flow rate, like a clogged pump, and generate an alarm.
    • Pump’s RPM comes from VFDs analog outputs.

    Common to all pumps

    • HTML file format reports, which can be opened in a Web browser or exported to Excel. The report to the right was downloaded this way and was not formatted.
    • Fits any control panel: small compact flow meter measuring 6 x 4 x 2.2 inches.
    • Integrated open channel flow formulas to calculate volume lost in SSO events.
    • Abnormal event detection with relay output:
    • Many anomalies are based on compiled history comparison
    • Hydraulic (high variation in pump capacity)
    • Energy (high variation in electrical consumption)
    • Efficiency (high variation in volume pumped per watt usage)
    • Alternation (pumps not alternating normally)
    • ON & OFF times (short pump start or stops)
    • Operating time (high variation not caused by inflow)
    • Level related anomalies
    • Improbability in results (e.g. water level falls while pumps are not in operation)
    • Internal battery charger for external battery to keep the level sensor and communication equipment powered during power failure.
    • Optional Remote Web monitoring, alarms, data download via our free scada software MaidMaps.
    • Communication options: Cellular modem, WiFi Modem, Telephone land line modem, Spread Spectrum Radio, Direct connect to Internet
    • TCP/IP MODBUS: Volumes, flow, capacities, efficiencies, starts, run times and all alarms can be reported in real time or totalized since last access.

    VOLUCALC RT uses the most advanced derived flow and volumetric flow algorithms ever patented.

    Our unique algorithm is used every time a flow calculation is performed for constant speed pumps, with analog level sensor or not.
    A calibrated mag meter is the only other technology as accurate, but only when pumps are in operation and you won’t get inflow, power consumption, efficiency or any abnormal behavior detection from a mag meter.

    When variable speed pumps are used, the accuracy is as high as the quality of the calibration performed. Pump curves must be readjusted to the reality of the station where the pumps are installed. In duplex and triplex variable speed pumps stations, Volucalc uses the efficiency of a pump to determine when that pump curve cannot be trusted anymore.


    • Inflow
    • Outflow
    • Volume
    • Run time
    • Starts
    • Energy consumption
    • Efficiency (G/watt)
    • Cost of operation ($/year)

    Name / Item No. Volucalc RT / MLRT


    Product type Real time volumetric flow meter, Open channel flow meter and derived flow, Efficiency based pump controller abckup.
    Types of recorded and displayed data (always time stamped) Flow, level, pump capacity, run time, number of starts, abnormal behaviours, time and volume of overflow, annual operational price in $.
    Volumetric flow accuracy (normal operation) ± 1.5 % for most lift station with inlet above pump operating levels.
    Open channel flow accuracy Based on level sensor specifications and flow equation used. Available formulas: Manning, California pipe, Rectangular weir with end contractions, Rectangular weir without end contractions, V-notch (or triangular) weir and Trapezoidal (or Cipolletti) weir or use a standard or polynomial flow formula or a lookup table.
    MaidMaps functions Email, SMS, geographic map displays pump operation
    Analog inputs 6 Total:4 x Pump current, 4-20mA, 0-5v, 0-10v, 0-24v

    2 x 4-20mA, 0-5v, 0-10v, 0-24v which are mostly used for level and pressure.

    Reading speed of analog input 40 Hz with average every second.
    Analog input accuracy ± 0.1 %.
    Number of digital inputs 1 used for rain
    Outputs 6 x digital, activated based on alarm setup or remotely activated with MaidMaps,1 x 4-20mA output self-powered.
    Alarms detected and displayedAction taken when alarms: Relay activation. With MaidMaps: email, SMS, colour changes on geographic map Level, extreme flow, Hydraulic (high variation in pump capacity), Energy (high variation in electricity consumption), Efficiency (high variation in volume pumped per watt used), Alternation (pumps not alternating normally), ON and OFF times (pumps start or stop for very short period), Operating time (high variation not caused by inflow), Number of starts per day has changed, Level related anomalies, Improbability in results (e.g. water level falls while pumps are not in operation).
    Internal temperature sensor accuracy ± 3°C
    Memory 2 Gb, 200 Million records
    Power supply 12 VDC 1 AMP (included), 12v battery backup.
    Integrated Battery Charger For 12v lead acid battery (MLBATRECH12V)
    Communication Interface USB drive and Ethernet
    TCP/IP MODBUS Volumes, flow, capacities, efficiencies, starts, run times and all alarms can be reported in real time or totalized since last access.
    Display Backlit graphic 128 x 64
    Keybord 4 soft keys
    Dimension (inches) 5.7 x 3.9 x 2.14
    Dimensions (cm) 14.5 x 9.9 x 5.5
    Weight 0.5 lb/0.22 kg
    Accessories Current sensor, pressure sensor, level sensor, Panel mounted brackets, Wi-Fi adaptor, cellular modem, MaidMaps geographic web server, MerMaid
    Warranty 3 years, parts and labor

    Item RTU Description COMPLY
    YES NO
    1.01 The RTU shall be a Volucalc RT or approved equivalent. X
    1.02 The RTU shall have a built in battery charger able to charge and keep the external replaceable sealed battery charged. X
    1.03 The RTU shall have a battery backup system capable of keeping the RTU, the communication hardware and the level sensor powered for 48 hours in case of primary AC failure. A different user selectable communication pattern can be set for battery operation. X
    1.04 The RTU shall be set to transmit immediately when abnormal conditions occur and at specific interval under normal conditions. X
    1.04 To record pump current, the RTU shall allow to set the pump inputs CTs for 15 Amps, 75 Amps, 300 Amps or for other custom values to be approved by RTU manufacturer. X
    1.06 A 12 VDC output shall be used to power the communication hardware and level sensor and switch automatically between AC power and battery power in the event of a power failure. X
    1.07 A pump specific relay output shall be activated when an abnormal condition is related to a pump, unless specified otherwise by the user X
    1.08 All abnormal conditions shall be displayed on the screen of the instrument and shall be acknowledge by the user to have access to the regular menu, unless specified otherwise. X
    1.09 A high variation in pump capacity shall generate an abnormal condition based on user specification. X
    1.10 A high variation in inflow shall generate an abnormal condition based on user specification. X
    1.11 A high variation in inflow based on averaged measured values shall generate an abnormal condition. X
    1.12 Higher than usual current draw shall generate an abnormal condition based on user specification. X
    1.13 Lower than usual current draw shall generate an abnormal condition based on user specification. X
    1.14 An abnormal sequence of operation of the pumps shall generate an abnormal condition. X
    1.15 Extremely long run time, based on average pump cycle time, shall generate an abnormal condition. X
    1.16 Extremely short run time shall generate an abnormal condition. X
    1.16 Wide variation in any compiled results shall generate an abnormal condition. X
    1.18 A high variation in volume pumped per watt used in any compiled results shall generate an abnormal condition. X
    1.19 An abnormal condition shall be generated when the level is falling and no pumps are in operation. X
    1.20 An abnormal condition shall be generated when the levels at which pumps were changing states have changed. X
    1.21 An abnormal condition shall be generated when the level have not changed for a long period. X
    1.22 The RTU shall be able calculate volumetric flow in real time within 2%, when a calibrated analog level sensor is connected to the RTU and constant speed pumps are used. X
    1.23 The RTU shall be able calculate a derived flow by integrating variable speed pump curves based on the pumps RPM supplied by the analog output of the VFDs. The accuracy is related to the precision of the pump curves entered in the configuration software and the optional availability of an analog level input and a force main pressure input. X
    1.24 The RTU shall be able calculate a derived flow using constant speed pump curves or preset capacities. The accuracy is related to the precision of the pump curves or capacities entered in the configuration and the optional availability of an analog level input and a force main pressure input. X
    1.25 The RTU shall be able to calculate flow using any open channel flow formulas. X
    1.26 The RTU shall be able to integrate all of the above flow formulas and display the resulting value on screen X
    1.27 The RTU shall have a 4 to 20 mA configurable analog output that can be set proportional to the flow calculated. X
    1.28 An abnormal condition shall be generated in the event of a change in analog value of more than a user specific value X
    1.29 Any change of the RTU digital inputs shall be transmitted to the central monitoring software immediately when the internet connection is available and ready. X
    1.30 The RTU shall have one (1) digital inputs that can be used as pulse counting totalizers, like for rain monitoring. X
    1.31 The RTU shall have 4 pump current inputs recording pump change of state in one (1) second resolution. X
    1.32 Unused pump inputs can be set to record analog values. User can select between 4-20mA, 0-5vdc, 0-10vdc and 0-24vdc for each of the pump inputs. X
    1.33 Installation brackets shall be available to install the RTU on an internal panel door, on a DIN rail, being bolted and in a NEMA 4X enclosure. X
    1.34 Transmit all data and alarms via any internet connection including wired, Wi-Fi, cellular (all technologies) and satellite. X
    1.35 Be powered by 12 to 24 volts DC. X
    1.36 Be supplied with a U.L. , ULC or CSA recognized 120 VAC to 12-24VDC 2A power supply X
    1.37 Have built in AC failure and low battery detection. X
    1.38 The RTU shall have6 analog inputs, 10-bit resolution, selectable between 4-20mA, 0-5 vdc, 0-10 vdc and 0-24 vdc, with a maximum cumulative of 64 alarm settings X
    1.39 The RTUs shall have four (4) relays used to suggest to the pump controller the most efficient way of using the pumps in order to reduce the energy consumption. The RTU shall activate the appropriate relay prior to reaching the starting level. X
    1.40 The RTU shall have two (2) additional relays. One can be used to supply power to the modem and level sensor during power failure. The other can be remotely activated by the user. X
    1.41 The RTU shall be able to set a user password to display the information on screen or to allow any modification of the configuration. X
    1.42 All data shall be recorded on flash memory with a minimum capacity of 2 Gb. The memory shall not be affected by power loss from AC or battery, internal or external. X  
    1.43 All settings, other than entering pump curves, can be configured with the RTUs keyboard. X  
    1.44 The keyboard keys shall be context sensitive. X  
    1.45 The display shall present the following type of information: Real time flow – Pump, flow and rain statistics – Power consumption – Configuration – I/O and communication tests – On screen reports – Alarms – USB transfer including settings, data and firmware upgrades. X  
    1.46 The default screen shall display level (with analog level sensor), when the next pump operation should occur, flow in and out, the state of all the relays and communication, date and time. X  
    1.47 The Real Time screen shall display the level, the force main pressure, the head, the flow rate and the current used by each pump in operation X  
    1.48 The Pump Statistics screen shall display for each pump and each combination of pumps the number of starts, run time, average flow rate, total volume that went through the displayed pump(s) and the actual flow rate. X  
    1.49 The Power Consumption screen shall display the electrical consumption in kWh and $. X  
    1.50 The Internal Information screens shall display the voltage powering the RTU, the voltage of the external battery used for power backup, the battery charging status, the status of the digital input, the value of the analog input used for pressure monitoring, the value of the level input and the internal temperature of the RTU. X  
    1.51 The Rain Statistics screen shall display total rain, last month rain, today’s rain and rain maximum intensity. A Reset button shall be available. X  
    1.52 If an analog level sensor is used for SSO monitoring, the Analog Sewage Sewer Overflow screen shall display the flow rate of the liquid lost, its minimum and maximum flow rate, total volume lost and number of events. X  
    1.53 If a digital level sensor is used (like a float) for SSO monitoring, the Digital Sewage Sewer Overflow screen shall display the duration of the last SSO event, when was the last event and the number of events. X  
    1.54 The Configuration screen shall allow the user to change the parameters related to: date, time, units, display settings, I/O, level setup, open channel flow setup, communication, alarms, reset cumulative and firmware upgrade. X  
    1.55 An HTML formatted reports shall be generated for each month with the following information: Stations settings, pump statistics (run time, volume, power consumption and electrical cost). For each day, it should have the power consumption, the energy wasted, the greenhouse gas generated because of the energy wasted, the percentage of use of the station, the maximum level reached, rain, total volume, average flow, minimum flow rate and time of occurrence, maximum flow rate and time of occurrence, average outflow of the pumps and totals or averages for all. For each pump and combination of pumps and for each day: Number of starts, total run time, run time alone, average current, volume, efficiency in Volume/kWh, average capacity of the day and totals and averages for all. For each alarm, it should have the name of the alarm, the beginning and ending time, duration, the reason (like level reached) and description. X  
    1.56 The USB screen shall allow to copy to the USB drive Digital events reports, Monthly flow reports, Monthly Volucalc reports, the Volucalc RT User Manual, MerMaid software compatible format data, Configuration, RAW and Technician data (for technical support). The USB screen shall allow copying configuration files and firmware updates from the USB drive. X  
    1.57 A Test screen shall allow testing of the analog output of the RTU. X  
    1.58 When communication is available with Maid Maps web server, the RTU shall be able to receive firmware upgrades and new settings. X  
    1.59 The antenna and mounting hardware shall be selected based on site’s requirements and communication device used. X
    1.60 The RTU shall be able of reporting alarms and all supervisory information to a password protected server web site supplied free of charge by Maid Labs Technologies Inc. X
    1.61 A free Windows based configuration software shall be supplied with the RTU. X  
    1.62 The user shall be able to install the server web site software on its own server station or use the free Maid Labs server. X
    1.63 The RTU shall have the TCP/IP MODBUS protocol and supply registry access to volumes, flow, capacities, efficiencies, starts, run times and all alarms, which all can be reported in real time or totalized since last access. X
    1.64 Be designed for ease of installation. X

    MLSOFTM Mermaid software
    MLMAP MaidMap software
    Power supply
    MLPS2 AC 12 VDC 1.5A
    Connectors (for current sensors)
    MLCTA2 Connector for one MLCT150 or MLCT300
    Current sensors
    MLCT150 Current Clamps 150 Amps
    MLCT300 Current Clamps 300 Amps
    MLCTP1500 Precision current sensors 1500Amps
    MLCT75 Mini current sensor 15A-75A
    MCELETH Cellular Modem with Ethernet port
    Other Accessories
    MLRG1 Rain gauge NWS approved
    MLPL Wastewater pressure sensor for level and force main
    MLSUPPANEL Brackets to fix Volucalc to panel door

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    Click on the picture below to download Volucalc RT in 3D. Specifications, including but not limited to components, display, connectors and accessories can change at any time. Some components might be there simply to help understand the concept.

    3D drawing available