Concrete Pump Line Calculator

How the concrete pump line calculator works

A pump pushes concrete down a steel line against friction, and every extra metre, bend, lift and length of hose adds to the pressure it needs. The calculator turns each of those into an equivalent length of straight steel line, adds them up, and asks what share of your pump's rating that uses. It does not guess a friction figure of its own. It takes the gradient from the pump: rated concrete pressure divided by the rated horizontal distance on the spec sheet.

Δp = (P ÷ R) × [(L − h) + 4h + 9 ft (2.74 m) × b + 3s]

L is the steel line length including any vertical runs, h the vertical part of it, b the number of 90° bends, s the end hose length, P the pump's maximum concrete pressure and R its rated horizontal distance. The answer is the pressure the line needs, and the share of the pump's rating it takes.

Where the equivalent lengths come from

The vertical factor comes from ACI 304.2R, the American Concrete Institute's guide to placing concrete by pumping: in its 1996 edition, each foot of vertical rise costs about three to four feet of horizontal distance, because it takes three to four times the pressure. The calculator uses four, the cautious end.

Bends and hose come from the American Concrete Pumping Association's Certified Operator Study Guide. A 90° sweep bend with a one metre radius creates as much pressure as nine feet of straight pipe, and rubber hose is three times as hard to pump through as steel, so ten feet of hose counts as thirty. The same guide gives a rule for the concrete standing in a riser: the static pressure at its base is about 1.1 psi per foot of height, roughly 0.25 bar per metre.

Why the pump rating is the yardstick

A pump's spec sheet gives its maximum pressure on the concrete and the distance it can push horizontally at that pressure. Divide one by the other and you have the pressure it spends per foot or metre of line in the conditions it was rated for. Where the sheet gives ratings for more than one line size, use the one for the line you are running. The 1996 edition of the ACI guide gives typical classes: small trailer pumps apply up to about 750 psi (52 bar) and reach around 1,000 ft horizontally or 250 ft vertically, medium-duty pumps up to about 900 psi (62 bar) and 1,200 ft horizontally or 300 ft vertically. The defaults use the medium-duty figures. Replace them with your pump's own numbers.

Check the factor against those figures and it holds. A 300 ft riser counts as 1,200 ft of horizontal line, which is exactly the medium-duty pump's rated reach.

A ground-level pour, worked through

A 5 in line runs 130 ft from a trailer pump to a slab, with four 90° bends and 10 ft of hose on the end. The equivalent length is 130 + 4 × 9 + 3 × 10 = 196 ft. With a 900 psi pump rated for 1,200 ft, each foot costs 900 ÷ 1,200 = 0.75 psi, so the line needs about 196 × 0.75 = 147 psi. That is 16% of the rating, plenty of margin.

A ten-storey pour, in metric

Now 120 m of 125 mm line, 35 m of it vertical up the core, six bends and 3 m of hose, on a pump rated at 85 bar and 400 m. Equivalent length: 85 m horizontal, plus 35 × 4 = 140 m for the riser, about 16 m for the bends and 9 m for the hose, roughly 250 m in all. At 85 ÷ 400 = 0.2125 bar per metre, that is about 53 bar, or 63% of the pump. The riser holds 35 × 0.249 ≈ 8.7 bar of static head at its base. Because it is taller than 100 ft (30 m), the ACPA guide calls for a concrete thrust block at the bottom.

Reading the result

Up to 80% of the rating shows as within range. Above 80%, up to and including 100%, it is flagged as at or near the limit, because a stiff load, a dry batch or the start of a blockage can push the pressure up quickly and most pumps cannot deliver their maximum pressure and maximum output at the same time. Over 100%, the line is beyond what the pump is rated for: shorten it, cut bends, lose hose, or bring a bigger pump or a boom. The 80% line is our judgement, not a published limit.

Line fill and aggregate size

The line fill is the volume of the bore over the steel line and hose. It is concrete that has to go in before any reaches the pour, and roughly what comes out at washout. The ACPA guide puts it at about half a cubic yard per 100 ft of 5 in line, and the calculator's 0.71 yd³ for 140 ft of 5 in line and hose matches it. Tell the ready-mix supplier, and plan a priming slurry ahead of the first load.

Aggregate size is limited by the bore. ACI 304.2R caps angular coarse aggregate at one third of the smallest inside diameter and rounded aggregate at two fifths, so a 125 mm line takes up to about 42 mm crushed or 50 mm rounded. Froehling & Robertson's notes on pumping concrete repeat that rule and add practical ones: a 12 ft end hose with at least 5 ft of it horizontal, and discharge from no more than 3 ft above the placement.

What this tool does not do

Real line pressure depends on the mix, slump, output rate, pipe wear and temperature, and none of those are modelled. The figure is a planning check that the pump and the line layout suit each other before the day. It does not rate the pipe, clamps or hose for pressure, set out outriggers, or design thrust blocks and line supports. Those belong to the pump operator and, for structural supports, an engineer.

Three layouts need more care than the formula gives them. A reducer, say from a 5 in to a 4 in line, adds resistance that is not counted here, and the ACPA guide names it as the first place to look when a line plugs. A run that descends earns no pressure credit: enter the rise only, and treat the descent as horizontal. ACI 304.2R warns against letting concrete free-fall down a descending line, because it breaks the flow and can knock air out of air-entrained mixes. And a boom pump is specified by its boom's reach, so use the calculator for any line run beyond the boom, not for the boom itself.

Using this calculator with other BuildMetricLab tools

The ready-mix truck calculator plans the deliveries the pump will take, and the slump calculator covers the consistency test on arrival. All BuildMetricLab tools run in your browser with no sign-up, and the formula is on the page so the maths can be checked.