Topic
Pumps
56 guides across the knowledge base.
Permissives
The conditions that must be true before a device may start: how permissives differ from interlocks and trips, the list a pump or feeder usually needs, coding them so the HMI can say why a start was refused, and the rules for time delays and bypasses.
9 min readUpdated Sep 5, 2026
CompactLogix
Field notes on the Rockwell Automation CompactLogix, the smaller Logix controller behind most lift stations and small plants: families and I/O, the two Ethernet ports, what it shares with ControlLogix and what it lacks, and what to check on site.
8 min readUpdated Sep 5, 2026
Deadband and Hysteresis
Why a single setpoint chatters, how a deadband turns it into a start point and a stop point, how wide to make it, and where deadbands belong in alarms, level control, and controller outputs.
7 min readUpdated Sep 5, 2026
Wet Well Level Measurement
How lift station wet well level is measured, which technology suits which well, the failure modes that flood a station, and why the high level float must stay hardwired.
8 min readUpdated Sep 5, 2026
Pressure Transmitters
Gauge, absolute, and differential pressure transmitters: how they sense, how range, turndown, and accuracy specifications work, the process connection and its accessories, and the installation errors that show up as calibration problems.
8 min readUpdated Sep 5, 2026
Hand-Off-Auto Selectors
What each position of an HOA selector does, how it is wired into the starter circuit, which protections must survive Hand, what the controller should see, and the mistakes that let a pump run with nobody watching.
7 min readUpdated Sep 5, 2026
Variable Frequency Drives in Pump Panels
What a drive adds to a pump panel and what it costs: speed control, soft start, reduced inrush, and diagnostics against heat, harmonics, cable and motor stress, bypass, and the minimum speed below which a pump does no work.
11 min readUpdated Sep 5, 2026
Soft Starters
Reduced-voltage solid-state starters: how they ramp a motor, what they do for inrush, water hammer, and mechanical stress, where they beat a drive and where they do not, bypass contactors, and the settings that matter on a pump.
9 min readUpdated Sep 5, 2026
Duplex Pump Panels
The duplex control panel: two pumps on one wet well and the sections every duplex panel contains, from power and starters through level control, alternation, hand-off-auto, alarms, and the backup float circuit to telemetry, with the failure responses.
9 min readUpdated Sep 5, 2026
Triplex Pump Panels
The triplex control panel: three pumps on one wet well, the alternation schemes that keep three pumps evenly used, staging levels and standby logic, power, drives and their coordination, the backup circuit for three pumps, and what a duplex never decides.
8 min readUpdated Sep 5, 2026
Alternation
Pump alternation at the panel level: what it is for, the alternator relay against controller logic, schemes from alternate-every-cycle to runtime balancing, manual lead selection, skipping a failed pump, alternation in the backup circuit, and the tests.
7 min readUpdated Sep 5, 2026
Distribution Pressure Control
How a booster or high service pump station holds discharge pressure with variable speed pumps, how pumps are staged, and what stops the system hunting.
9 min readUpdated Sep 5, 2026
Tank Level Control
How a storage tank is filled and drawn on level setpoints, how the setpoints are chosen to keep the water turning over, and what the station does when the tank stops talking.
8 min readUpdated Sep 5, 2026
Lift Station Lead/Lag Control
How a duplex or triplex station decides when one pump is enough and when it is not: the setpoint ladder, cycle volume, the lag call, parallel pumping, and what to do when the lead pump fails.
12 min readUpdated Sep 5, 2026
Lift Station Pump Alternation
Which pump leads, how the lead role rotates, what an alternator relay does, and why equal run hours are not always the goal. Includes the logic rules that keep alternation from causing trouble.
10 min readUpdated Sep 5, 2026
Wet Well Level PID Control
Holding a wet well level with a variable speed pump instead of bang-bang control: the loop structure, the minimum speed floor, the stop and restart logic at low inflow, tuning for a slow integrating process, and where level PID is the wrong idea.
11 min readUpdated Sep 5, 2026
VFD Pump Control in Wastewater
The control modes for a variable speed wastewater pump: level control, flow pacing, fixed speed with soft start, and drawdown modes, plus the wastewater-specific rules: minimum speed, ragging at low speed, force main velocity, and the periodic full-speed run.
10 min readUpdated Sep 5, 2026
Triplex Lift Station Controls
What changes when a station has three pumps: the lead, lag, and standby roles, rotation with three positions, the diminishing return of the third pump on the system curve, availability logic, and the power and panel arrangements that three pumps require.
10 min readUpdated Sep 5, 2026
Well Pump Control
Controlling a groundwater well: submersible and line-shaft turbine pumps, the pump-to-waste start, drawdown and the low-water cutoff, cycling limits from the well and the aquifer, and what the controller monitors to protect a pump that cannot be seen.
10 min readUpdated Sep 5, 2026
Booster Pump Stations
Inline stations that raise pressure from one zone to another: suction pressure protection, discharge pressure control with drives, staging, the hydropneumatic tank alternative, surge and check valve behavior, and the interlocks that keep a booster from collapsing the zone it draws from.
9 min readUpdated Sep 5, 2026
RAS and WAS Control
Return and waste activated sludge: what each flow does for the process, RAS control by influent flow ratio or by blanket level, WAS control to a target sludge age or a target mixed liquor concentration, the flow and solids measurements each needs, and the pump and valve arrangements that make the setpoints achievable.
10 min readUpdated Sep 5, 2026
Wells
Operating a wellfield as a water source: selecting and rotating wells, pump-to-waste on start, drawdown and specific capacity, wellhead chemical feed, blending for nitrate or arsenic, the telemetry a well needs, and the interlocks that protect the pump.
10 min readUpdated Sep 5, 2026
Chemical Feed
Chemical feed from the control side: the chemicals and where they go, metering pumps and dry feeders, flow pacing with residual trim, the dose arithmetic, day tanks and drawdown tests, loss-of-feed detection, interlocks, and overfeed protection.
11 min readUpdated Sep 5, 2026
High Service Pumping
Pumping finished water into distribution: the control modes of tank level, pressure, and flow, how they interact with the clearwell and contact time, staging and surge, the telemetry the station depends on and its fallback, energy scheduling, and the alarms.
10 min readUpdated Sep 5, 2026
High Service Pumps
The pumps that carry finished water into distribution: types, the pump curve against the system curve, best efficiency point, the affinity laws and where a drive pays, parallel operation, valves, protection, and the efficiency monitoring that shows wear.
11 min readUpdated Sep 5, 2026
VFD Control for Water Pumping
Variable speed pumping and where it earns its cost: the affinity laws and how static head limits the savings, the minimum speed a pump can run, pressure, flow, and level control with a drive, and how to estimate the savings before buying.
9 min readUpdated Sep 5, 2026
Flow Control in Water Pumping
Controlling the flow a pumping system delivers: speed against valves, flow-paced pumping to a treatment rate, the flow loop with its ramp limits and its meter placement, and the loop tuning that keeps a flow controller steady.
8 min readUpdated Sep 5, 2026
Ground Storage Tanks
Controls for ground storage tanks: level measurement and its datum, filling from wells and treatment by pump control or altitude valve, and the telemetry that ties the tank to the system.
8 min readUpdated Sep 5, 2026
Pump Sequencing for Storage
Sequencing the pumps that fill and draw from storage: staging on level bands, rotating wells and sources for even use and water quality, time-of-day and demand-based scheduling, and the records that show the sequence is doing its job.
8 min readUpdated Sep 5, 2026
Reverse Osmosis
Reverse osmosis from the controls side: what the skid contains, the instruments that matter, the numbers an operator watches, recovery, rejection, normalized permeate flow, and the trends that say when the membranes need cleaning or replacement.
10 min readUpdated Sep 5, 2026
Membrane Feed Pumps
The high-pressure feed pumps of a membrane plant: multistage centrifugal pumps on drives, the pressure ramp that protects the elements, suction protection and the cartridge filters ahead of them, and the maintenance that the trends point to.
8 min readUpdated Sep 5, 2026
Constant Speed Pump Control
On and off pumping with constant speed pumps: why it remains the right answer at most lift stations, the level bands and the wet well volume that set the cycle, starts per hour and motor limits, and the cases where variable speed is worth its cost.
8 min readUpdated Sep 5, 2026
Station Flow Control
Controlling the flow a lift station sends downstream: why a station would limit or match its flow, the plant hydraulic limit, the force main capacity, equalization, and wet weather, and the alarms.
8 min readUpdated Sep 5, 2026
Pump Sequencing Strategies
The strategies for sequencing wastewater pumps: level bands with alternation, lead and lag and standby with runtime balancing, a drive lead with constant speed lag, pump-down against steady-flow operation, and how each strategy fails and recovers.
9 min readUpdated Sep 5, 2026
Manual Operation Procedures
Written procedures for running the plant and the remote sites without the SCADA or the controllers: what to read and set by hand, how often to check, what to log, chemical dosing from a flow reading, when to stop, staffing, and the drill that proves them.
9 min readUpdated Sep 5, 2026
How to Build Pump Graphics
Build a pump symbol and faceplate that operators can read at a glance and use without error: a symbol that shows state by shape and a muted palette with color reserved for abnormal, and a test against the high-performance HMI principles before it is deployed.
8 min readUpdated Sep 5, 2026
Pump Will Not Start
A pump that is called and does nothing. The order to check: permissives and mode, control power, the starter or drive, the motor circuit, and the pump itself, with the measurements that settle each one in minutes.
10 min readUpdated Sep 5, 2026
Pump Runs But No Flow
The motor turns and nothing moves. How to tell a clogged impeller from an air-bound pump, a closed valve, a stuck check, a broken coupling, or reverse rotation, using motor current and discharge pressure before pulling anything.
10 min readUpdated Sep 5, 2026
Pump Short Cycles
A pump that starts and stops far more often than it should: the control band, the level signal, a leaking check valve, a waterlogged pressure tank, a lag pump doing the lead job, and the starts-per-hour limit that makes short cycling a motor killer.
9 min readUpdated Sep 5, 2026
Drive Will Not Start in AUTO
The drive runs from the keypad or in HAND but not from the controller. The command source, the enable and safe torque off inputs, the speed reference, and the network control word, checked in the order that finds the problem fastest.
9 min readUpdated Sep 5, 2026
Drive Faults on Overcurrent
An overcurrent trip on a variable frequency drive: what the drive measured and when, the difference between a trip at start, during acceleration, at steady speed, and at deceleration, the motor and cable faults behind each, the parameter settings that cause nuisance trips, and the tests that separate them.
9 min readUpdated Sep 5, 2026
Drive Faults on Overvoltage
A DC bus overvoltage trip on a drive: where the bus voltage comes from, why deceleration and a driving load raise it, the utility-side causes from a high supply and capacitor switching, the deceleration ramp and overvoltage controller settings, braking resistors, and how to tell a regeneration trip from a supply transient.
9 min readUpdated Sep 5, 2026
Motor Will Not Reach Speed
A drive that runs but never gets the motor to the commanded speed: the reference and its scaling, the maximum frequency and speed limits, current limit holding the ramp, a load beyond the motor, a wrong motor parameter set, and a low supply, with the drive readouts that separate them.
9 min readUpdated Sep 5, 2026
Drive Trips on Ground Fault
A ground fault trip on a variable frequency drive: how the drive detects it, the motor and cable insulation faults behind most trips, the submersible cable problem, the capacitive leakage on long cables and filters that produces nuisance trips, wiring errors, and the insulation test that decides it.
9 min readUpdated Sep 5, 2026
Loss of Control Voltage
Control voltage that drops out for a moment and comes back, resetting controllers and dropping contactors: utility sags when a large load starts, a transfer switch operation, a loose neutral, or an overloaded control transformer. Catching it with a recorder.
8 min readUpdated Sep 5, 2026
Voltage Sag on Motor Start
Lights dim, contactors drop, and controllers reset every time the big pump starts: the starting current of an across-the-line motor pulling down a weak source. Measuring the sag, checking the source, and fixing it with a soft starter or ride-through.
8 min readUpdated Sep 5, 2026
Pump Loses Prime
A suction-lift pump that runs without pumping, or pumps for a while and then stops: air leaking into the suction line, a foot valve that lets the line drain, a lift too high, a vortex or an aerated inflow, or a self-priming casing that lost its charge.
8 min readUpdated Sep 5, 2026
Seal Failure Alarm
The moisture probe in a submersible pump has tripped its relay: a seal that is leaking, or moisture in the cable, the junction box, or the probe circuit, a relay that does not match the pump, or a failed relay. What the alarm should do and what to check.
8 min readUpdated Sep 5, 2026
Both Pumps Running Constantly
A duplex station where lead and lag run together and never catch up: inflow beyond one pump, pumps that lost capacity to wear or rags, a force main partly blocked, a pump that runs but does not pump, a level stuck high, or bad setpoints. The drawdown test.
8 min readUpdated Sep 5, 2026
Actuator Torque Fault
An electric actuator that trips on torque: at the seat because the seating mode or setting is wrong, in mid-travel because something is in the way or the stem binds, or under flow because the differential exceeds the sizing. The checks before a reset.
8 min readUpdated Sep 5, 2026
The Tank Level Trend Tells the Whole Story
One trend, a storage tank level over a week, holds most of what an operator needs to know about a water system: demand, source capacity, leaks, pump health, water age, and why it deserves a permanent place on the main screen.
8 min readUpdated Sep 5, 2026
Inflow and Infiltration Shows Up in the Pump Runtime
Most small collection systems have no flow meters at the lift stations, but every station reports pump runtime and starts to SCADA. How to turn those two numbers into a station flow estimate, and rank where the money for pipe work should go.
9 min readUpdated Sep 5, 2026
Duplex Lift Station Controls
The two-pump station that makes up most of a collection system: what is in the panel, how the sequence works, what is monitored, and where these stations actually fail.
11 min readUpdated Aug 27, 2026
How to Program Lead/Lag Pump Control
Build duplex pump control with alternation, failure detection, minimum run and off timers, and an operator override that survives a restart.
10 min readUpdated Aug 24, 2026
PID Control for Pumps and Valves
What each term actually does, how to tune a loop on a real pump station, and the handful of mistakes that cause most of the oscillation people blame on tuning.
11 min readUpdated Aug 19, 2026
Lead/Lag Pump Control
Which pump runs first, when the second joins, how they trade places, and the design decisions that determine whether a duplex station wears evenly.
9 min readUpdated Aug 18, 2026
Other topics
Direct contact
Have a controls question?
Reach Eric Sullivan directly about anything on this site, a controls or automation topic, or one of his personal projects.