Common Pump Types Reference
Why this matters
Pumps move water + waste + condensate + heating fluid in every service trade. Wrong pump = won't deliver flow OR pressure; oversized = wastes energy + short-cycles. The tech who knows pump types + sizing diagnoses + recommends correctly. This is the field card.
Pump categories
Centrifugal: rotating impeller; flow + pressure tradeoff; most common.
Positive displacement: piston, diaphragm, gear, screw - delivers fixed volume per cycle; constant flow regardless of pressure.
Submersible: motor + pump in one unit, designed to operate underwater.
Surface (above-ground): motor + pump mounted dry; connects to water via suction line.
Centrifugal pump types
End-suction centrifugal: workhorse of HVAC + commercial. Single impeller. Bell + Gossett, Taco, Armstrong common brands.
Inline circulator: small centrifugal mounted directly on pipe; HVAC hydronic. Quiet, low-cost.
Self-priming: pulls suction lift on startup; for irrigation + above-ground pool.
Booster pump: increases pressure to existing system; whole-house OR irrigation.
Sump pump: drains basement sump pit. Submersible OR pedestal style. 1/3 - 1/2 HP residential.
Pump curves
Flow (GPM) on x-axis; head (ft OR PSI) on y-axis. Pump delivers varying flow depending on system back-pressure.
Best Efficiency Point (BEP): where pump runs most efficiently. Should be > 80% of pump's max efficiency.
Operating point: intersection of pump curve + system curve. Sized correctly.
Run too far right of BEP: low pressure, high flow, possible cavitation.
Run too far left of BEP: high pressure, low flow, recirculation + overheating.
Sizing by GPM + head
Required flow (GPM): from fixture demand OR HVAC system flow rate.
Required head:
- Vertical lift × 1 ft = 0.434 PSI
- Pressure drop through pipes (friction loss tables)
- System pressure differential
Example - basement sump:
- 3 ft vertical lift
- 50 ft horizontal 1-1/2" PVC: 1 ft friction loss / 100 ft = 0.5 ft loss
- Total head: ~ 3.5 ft
- Need: 30 GPM at 3.5 ft head
- Sump pump 1/3 HP delivers 35 GPM at 5 ft head - sized correctly
Standard residential pumps
Sump pump: 1/3 - 1/2 HP; 30 - 60 GPM at 5 ft. Common: Zoeller M53, Wayne CDU800, Liberty 257.
Sewage ejector (waste): 1/2 - 1 HP; handles solids up to 2"; bathroom below sewer line.
Effluent pump (septic): 1/3 - 1/2 HP; effluent from septic tank to drain field; no solid handling.
Well pump: 1/2 - 1.5 HP submersible OR jet; depends on depth + flow demand.
Booster pump: 1/2 - 1 HP centrifugal; whole-house pressure boost.
Pool pump: 1 - 2 HP; circulates pool water through filter + heater.
Spa / hot tub pump: 1.5 - 3 HP; jets + circulation.
HVAC condensate pump (mini-split, high-eff furnace): 1/30 - 1/15 HP; tiny but critical.
Hydronic circulator: 1/40 - 1/8 HP per zone; boiler heating system.
Fountain / waterfall: 1/8 - 1 HP submersible.
Sump + sewage pump install
Pit sizing: 18" min diameter × 22" deep (sump) / 24" × 30"+ (ejector).
Check valve: prevents backflow when pump cycles off. Above pump.
Vent: ejector pit must vent through roof per IPC (sewer gas).
Float switch: tethered float OR vertical pole + switch. Tethered easier service.
Alarm: high-water alarm (battery OR plugged-in) on critical sump.
Battery backup: separate battery-powered backup pump for power-outage events. Critical for basements.
Well pump install
Submersible well pump: pumped from well casing; pressure tank in basement.
Pressure switch: 30/50 PSI typical (40/60 PSI higher pressure); cuts pump on at 30, off at 50.
Pressure tank: 20 - 80 gal; air-cushion bladder. Pre-charged to 2 PSI below cut-in.
Pitless adapter: well-head fitting; horizontal pipe exits well casing below frost.
Pool + spa pump
Single-speed: full GPM all the time. Old standard; energy-wasteful.
Two-speed (high/low): low for circulation; high for vacuuming.
Variable speed: motor adjusts RPM to demand. Saves energy. Required new pool builds many jurisdictions.
Turnover rate: pool volume / pump GPM = hours to filter entire pool. Target 8 - 12 hours.
HVAC condensate pump
Float switch in collection pan + pump up: discharges through 1/4" - 3/8" tubing to drain.
High-level alarm switch: shuts off AC if pump fails (prevents flood).
Common brands: Little Giant, Aspen, RectorSeal.
Pump maintenance
Sump: test float annually; clean pit (debris clogs impeller); replace every 5 - 7 years.
Well: test pressure tank annually (low pre-charge = short cycle); pump impeller wear 10 - 20 years.
Pool: clean strainer basket weekly; impeller inspection annually; replace 7 - 10 year service life.
Hydronic circulator: bleed air annually; check shaft + seal for leaks.
Common pump problems
Pump runs constantly: leak in plumbing OR pump cycling at low flow.
Pump won't start: capacitor failed, motor seized, control board issue, float stuck.
Hum but no spin: locked impeller (debris OR rust); manually free.
Low pressure / flow: clogged impeller, leak in suction line, low refrigerant pressure (cooling pumps), incorrect impeller for pump.
Loud noise / vibration: cavitation (pump running off curve), worn bearings, unbalanced impeller.
Cavitation
When pressure at impeller falls below vapor pressure → liquid flashes to vapor → bubbles → collapse on metal → erosion + noise + vibration.
Causes: undersized suction line, high suction lift, clogged screen, suction temperature too high.
Fix: larger suction pipe, lower suction lift, flooded suction, lower temp.
Truck stock for pump work
Sump pump 1/3 HP + 1/2 HP; pressure switch (30/50, 40/60); pressure tank bladder repair kit; condensate pump assembly; PVC sump piping (1-1/2", 2"); check valves (multiple sizes); float switches; multimeter; capacitor tester.
Pump selection workflow
- Calculate required GPM (fixture demand OR equipment specs)
- Calculate required head (vertical lift + friction loss)
- Apply margin (10 - 20% for future load OR friction underestimate)
- Select pump where operating point is near BEP
- Verify electrical requirements + outlet location
- Specify check valve, vent, alarm as required
The single most-impactful pump habit is the AIR-CHARGE CHECK on every pressure tank service call. Customer's "pump short-cycles" complaint is 80% of the time a deflated pressure tank, not a failed pump. Use a regular tire-pressure gauge: shut off pump, drain tank to 0 PSI, check air charge - should be 2 PSI below cut-in pressure (typically 28 PSI for 30/50 system). Re-pressurize with bicycle pump OR shop air if low. 10 minutes + in parts = solved problem, saved customer the pump replacement they were quoted.
References
- Hydraulic Institute pump standards
- ASHRAE 90.1 (efficiency requirements)
- IPC + NEC for pump install
- Manufacturer pump curves (Bell + Gossett, Taco, Grundfos, Goulds, Zoeller)
- Manuall internal: Water Pressure + Flow, Pipe Sizing Reference