Line Pump vs Boom Pump: Which Is Right for Your Job?

How big a stone can a 3-inch pump line carry? Under the American Concrete Pumping Association (ACPA) one-third rule, the answer is 1 inch (3 / 3 = 1). That rule, plus a few sourced figures, explains more about the two pump types than their names do.

What Is a Line Pump?

A line pump, in the ACPA operator study guide (version 03.11), pumps grout or a 3/8-inch pea gravel mix through pipe and hose that is 2, 2-1/2 or 3 inches in diameter. The guide lists small interior or exterior slabs, shotcreting, block filling, tank filling, pressure grouting and soil stabilization among its uses.

The same guide gives setup advice for trailer pumps. Place the pump where two ready-mix trucks can reach it, if possible, and keep the placing line "as short and straight as possible". ACPA says pumping through rubber hose is three times as hard as through steel pipe. So 10 feet of rubber hose equals 30 feet of pipe in pumping effort (10 x 3 = 30).

Note that "trailer pump" and "line pump" are not strictly the same thing. The ACPA guide also names a trailer pump with a placing boom.

What Is a Boom Pump?

A boom pump is a truck-mounted concrete pump with an articulating placing boom. The ACPA guide refers to three-, four- and five-section boom pumps. No ACPA boom-pump definition was read, so none is attributed to ACPA here.

Putzmeister describes its BSF 38-5 as a truck-mounted pump for medium to high-volume concrete pours. That description covers that model only. To budget a pump job once you know the type, the Concrete Pump Cost Calculator exists for that purpose; the type facts here come from ACPA and Putzmeister, not from the tool.

How Does Aggregate Size Set the Line Diameter?

ACPA says the placing line should be at least three times, and preferably four times, the size of the largest aggregate in the mix. The guide also frames it the other way: the largest coarse aggregate is limited to one-third of the smallest inside diameter of the pump or placing line.

The sums below are arithmetic on ACPA’s rule, not extra ACPA figures:

1. ACPA’s own example. 1-1/2 in aggregate x 3 = 4-1/2 in minimum line (1.5 x 3 = 4.5).
2. The preferred four times. 1-1/2 in x 4 = 6 in (1.5 x 4 = 6).
3. Pea gravel. 3/8 in x 3 = 1-1/8 in (0.375 x 3 = 1.125); 3/8 in x 4 = 1-1/2 in (0.375 x 4 = 1.5).
4. A 3 in line, worked backward. 3 / 3 = 1 in aggregate at the three-times rule; 3 / 4 = 0.75 in at the four-times rule.

What Do Two Putzmeister Models Show?

Putzmeister’s published figures show how far apart two pumps can sit, and each belongs to its own model. Reach, output and aggregate limits differ by model, so neither set below stands for all pumps.

• Putzmeister BSF 38-5 (truck-mounted boom pump). Vertical reach 37.5 m and horizontal reach 32.8 m, with a DN 125 delivery line. Output is 160 to 170 cubic meters per hour depending on configuration. The page states no maximum aggregate size.
• Putzmeister TK 20 (Thom-Katt trailer-mounted concrete/shotcrete pump). Output up to 13 cubic meters per hour, delivery pressure 139 bar, maximum aggregate 25 mm and a 102 mm pressure connection.

My arithmetic, not Putzmeister’s: 37.5 m x 3.281 = 123.0 ft; 32.8 m x 3.281 = 107.6 ft; 125 mm / 25.4 = 4.9 in; 25 mm / 25.4 = 0.98 in (about 1 in); 102 mm / 25.4 = 4.0 in.

The TK 20 is a high-pressure grouting and shotcrete trailer pump. Putzmeister calls it suited to wet-process refractory, underground and civil work. It is not a typical slab line pump, and its 4.0 in connection is larger than the 2, 2-1/2 and 3 inch sizes in ACPA’s line-pump definition. Both pages read were Putzmeister regional sites (Turkey and Southeast Asia) with metric specifications.

What Safety Rules Apply to Boom Pumps?

ACPA’s position is that placing booms shall never be operated within 20 feet of energized overhead power lines, or 50 feet when the voltage exceeds 350 kV. ACPA also says contact with high-voltage power lines is the most common cause of fatal and serious accidents involving placing booms.

The study guide adds that a dedicated spotter is employed when wires are within 20 feet of the area to be poured. ACPA also says to tell the pumping company about power lines when ordering the pump and to remind the operator on arrival.

For the ground, the guide says to extend all outriggers fully and use the manufacturer’s pads, even on concrete. Relocate the pump when the outriggers cannot be stabilized. The guide says truck-mounted boom pumps are required to be level within three degrees. Near an open cut, set the outriggers back at least the depth of the ditch. The guide also states that a boom of 50 m or larger can put over 60,000 pounds on one outrigger.

What Does ACPA Say About Pumpable Mixes?

ACPA says the properties of the fine aggregate matter more than the coarse aggregate when proportioning pumpable mixes. The guide adds that an admixture that improves workability generally improves pumpability.

On air, the guide says entrained air up to six percent generally makes a mix more pumpable, while low-slump mixes above eight percent air are difficult to pump. This article states no slump number because none was read for ordinary pumped concrete.

On water, ACPA says it should only be added by the contractor or a designated representative. Excess water raises the water-cement ratio, which can lead to lower strength and excessive shrinkage. The operator may advise on mix design or slump, but the guide gives the contractor final responsibility. For the water side of a mix, see how much water per bag. For how ready-mixed concrete differs from bagged mix, see ready-mix vs bagged concrete.

FAQs About Line Pumps and Boom Pumps

Sources and Further Reading

This article summarizes ACPA guidance and figures for two named Putzmeister models, not every pump. Pump limits depend on the model and the line size, so confirm reach, hose size and aggregate with your pumping contractor. Reviewed for accuracy by Prof. Dr. Khalil Mudassar, PhD. Last updated 2026-10-21.