Pump terms in plain English
You do not need to be a pump engineer to buy the right pump
Our quote form asks for a duty point, total head and solids size. If any of that is unfamiliar, here is what each term means and why we ask for it. Do not have the numbers? Describe the job in your own words — how much water, how far, how high, how dirty — and our Houston team works it out with you.
We reply the same business day. Need it now? Call 713-690-7575.
9 terms
Sizing a pump
These four numbers are all we need to name a model, an impeller and a drive.
- Duty point
- The one combination of flow and pressure your job actually needs — for example 1,200 gallons per minute against 90 feet of head. It is a single point on a pump's performance curve.Give us the duty point and we can name the model, impeller trim and drive instead of guessing from pump size alone.
- Flow (GPM)
- How much water has to move, in US gallons per minute. Sometimes written as GPM, or as MGD (million gallons per day) on municipal work.Flow drives pump size and discharge diameter. 1 MGD is about 694 GPM.
- Total dynamic head (TDH)
- The total pressure the pump has to work against, expressed in feet of water. It is the vertical lift plus the friction losses in the suction and discharge hose or pipe, plus any pressure at the outlet.Two jobs with the same flow can need completely different pumps once head is included. Height alone is not head.
- Static lift
- The straight vertical distance the water has to be raised, measured from the water surface to the discharge point, ignoring pipe friction.It is the starting number for total dynamic head — friction loss gets added to it.
- Friction loss
- Pressure lost as water rubs against the inside of hose, pipe and fittings. Longer runs, smaller diameters and more elbows all increase it.This is why hose length and diameter matter as much as lift. Tell us the run length and size and we account for it.
- Suction lift
- How far above the water surface the pump itself sits. A pump can only draw water up so far before atmospheric pressure runs out — practical limits are usually in the region of 25 feet.High suction lift changes which pump and which priming system will work at all.
- NPSH
- Net positive suction head: the pressure available at the pump inlet. Too little and the water flashes to vapour inside the pump.Long suction lines, hot water and high altitude all reduce it.
- Cavitation
- Vapour bubbles forming and collapsing inside the pump because inlet pressure is too low. It sounds like gravel in the casing and it pits the impeller.Chronic cavitation destroys impellers and wear plates — usually a suction or sizing problem, not a build-quality one.
- Performance curve
- The chart showing what a given pump will deliver: flow across the bottom, head up the side, with lines for impeller size, efficiency and required horsepower.We pick a pump so your duty point sits in the efficient middle of the curve, not out at the end of it.
6 terms
Pump construction
- Wear plate & wear ring
- Replaceable metal faces sitting behind and around the impeller. They take the abrasion instead of the casing and are adjustable or renewable in the field.Restoring the clearance between impeller and wear plate is the cheapest way to recover lost performance.
- Impeller
- The rotating part that actually moves the water. Diameter and vane shape determine how much flow and head the pump produces.Trimming or changing an impeller re-points a pump onto a different duty without replacing the unit.
- Volute
- The spiral casing around the impeller that converts speed into pressure and routes the water to the discharge.Abrasive service eventually wears the volute — it is a replaceable part, not a scrap trigger.
- Mechanical seal
- The sealed cartridge that keeps water in the pump and out of the bearings, usually running in an oil-filled chamber.Seals are the most common scheduled replacement item; they are the core of our one-year and two-year spare kits.
- Rotating assembly
- The shaft, bearings, bearing bracket, seal and impeller as one pre-built unit.Swapping a rotating assembly returns a pump to service in hours instead of days.
- Non-return valve (NRV / check valve)
- A ball or flapper that stops water running back down the discharge line when the pump stops.Worn NRV balls and seats cause slow re-priming and loss of prime overnight.
4 terms
Priming & solids
- Solids passage
- The largest solid object the pump will pass through without plugging, given as a diameter — for example 3 inch spherical solids.Trash, sewer bypass and mine dewatering all live or die on this number.
- Auto-priming (Dri-Prime style)
- The pump clears air from the suction line by itself, repeatedly and unattended, using a vacuum or compressor system. It can run dry, sit idle, and re-prime when the water comes back.This is what makes a pump suitable for unattended bypass and stormwater standby duty.
- Self-priming (trash pump)
- The pump re-primes using water retained in its own casing after the first manual fill. Simpler and cheaper than auto-priming, but it needs water in the casing to start.Ideal for attended construction dewatering and trash duty with big solids.
- Dry-run capability
- The seal arrangement tolerates running with no water in the pump for a period without destroying itself.Essential where the water level rises and falls and nobody is on site to shut the pump down.
5 terms
Buying & service
- Rotating assembly interchangeability
- A replacement part built to the same fits, dimensions and tolerances as the original equipment part, so it installs in the existing pump with no modification.It is how you keep an existing fleet running without replacing the pumps themselves.
- OEM cross-reference
- A table matching the part number stamped on your existing part to the equivalent part number from another manufacturer.Send us the number from your old parts list and we identify what fits — model and serial confirm the exact build.
- Bill of materials (BOM)
- The numbered parts list that goes with an exploded-view drawing: item number, description, part number and quantity.Find your item number on the drawing, then order by that number.
- Lead time
- How long from order to shipment. Stocked items ship from inventory; made-to-order items are built to your configuration.We quote lead time with the price so you can plan the outage.
- Submittal package
- The document set an engineer or general contractor requires for approval: equipment schedule, performance curves, materials of construction, drive details and manufacturing statements.We issue these per model so specification review does not hold up your order.
Still not sure?
Tell us the job, not the specification
“I need to keep a 20-foot excavation dry, the water has mud and gravel in it, and it has to discharge 300 feet to a ditch” is enough information for us to start. Send that and we come back with the model, the flow it will hold and the price.
We reply the same business day. Need it now? Call 713-690-7575.
Continue exploring
- Pump selector
Enter flow, head and solids size and see which AMCO models fit.
- Parts cross-reference
Match an OEM part number to the AMCO part that replaces it.
- Manuals & literature
IOM manuals, parts lists, submittal packages and spec sections.