Grundfos SCALA is the best-selling all-in-one booster line for homes and light-commercial buildings — a self-priming pump, motor, tank, check valve and control in one enclosure, with no separate pressure switch or external tank to plumb. SCALA2 is a variable-speed system that holds constant pressure at every tap and runs at just 44 dB(A); SCALA1 is a fixed-speed, twin-capable booster with Bluetooth and an external input for float and irrigation control. Both self-prime from up to 26 ft, use 1 in NPT ports, and are certified to NSF/ANSI 61 and 372 for drinking water. Watermain Supply sells the U.S. 60 Hz range in 115 V and 230 V with engineering-led sizing to your fixture count, elevation and inlet pressure. Not sure which model fits? Call 1-888.510.4036 and we will size it for you.
SCALA1 and SCALA2 — all-in-one self-priming boosters that put steady water pressure at every tap. Grundfos’ best-selling home and light-commercial booster line, sized to your fixture count, elevation and inlet pressure.
2 SystemsSCALA1 & SCALA2
26 ftSelf-priming lift
15.8–23.5 GPMNominal flow
Up to 180 ftMax head, 60 Hz
NSF 61 / 372Drinking water
Grundfos is a Danish pump manufacturer and one of the largest in the world. SCALA is its integrated domestic and light-commercial booster platform: a multistage pump, motor, small pressure vessel, non-return valve and electronic control packaged in a single self-priming enclosure. There is no separate pressure switch or external tank to plumb — connect suction and discharge, set the pressure, and the system delivers water on demand.
The line splits into two systems. SCALA1 is a fixed-speed booster with Bluetooth, an external input and electronic twin-pump capability. SCALA2 is a variable-speed unit that holds constant pressure at every tap regardless of inlet fluctuation, at one of the lowest noise levels in its class. Watermain Supply offers the U.S. 60 Hz range with NPT connections and U.S. plugs, backed by engineering-led sizing to your fixture count, elevation and inlet pressure. Compare the two below, or call 1-888.510.4036 and we will size it for you. Genuine Grundfos equipment, factory-new in original packaging — sold and supported by Watermain Supply, an independent industrial supplier.
The SCALA Line
Two all-in-one platforms on the same self-priming, integrated concept — one fixed-speed and twin-capable, one variable-speed for constant pressure.
SCALA1
Fixed-speed, twin-capable booster
15.8–23.5 GPMnominal flow
150–180 ftmax head (60 Hz)
2 Models3-45 & 5-55
115 / 230 V1-phase
A self-priming multistage booster that packs pump, water-cooled motor, small vessel, check valve and controls into one composite enclosure. Fixed-speed operation with Bluetooth (Grundfos GO) and an external input for float-switch and irrigation control. Two units pair into an electronic twin booster for standby duty or higher flow. Runs under 55 dB(A), self-primes from 26 ft of lift, 1 in NPT ports.
Available models
SCALA1 3-45 — 15.8 GPM at 82 ft nominal, 150 ft max head
SCALA1 5-55 — 23.5 GPM at 82 ft nominal, 180 ft max head
Max inlet pressure 43.5 psi (3-45) / 29 psi (5-55)
Max system pressure 116 psi, self-priming to 26 ft
Electronic twin, Bluetooth, external input, IP X4D
NSF/ANSI 61, 372, CSA, CE
Best forHomes on city water with low street pressure, tank- and roof-fed systems, shallow wells, irrigation and water transfer, and installs that may need a standby or higher-flow twin.
A fully integrated variable-speed booster. An integrated pressure sensor and inverter adjust motor speed continuously to hold a constant set point across the whole home, with soft starts and steady flow even as inlet pressure swings. Aluminum-and-composite build, integrated diaphragm tank, one of the quietest boosters in its class at under 44 dB(A). Self-priming to 26 ft, 1 in NPT ports adjustable by up to 5 degrees.
Key specifications
SCALA2 3-45 — single model, 115 V or 230 V
Default set point 43 psi; maximum set point 51 psi
Max system pressure 145 psi, max inlet 87 psi
P1 550 W, IP X4D outdoor rated, 22 lb
Dry-run, micro-leakage and 30-minute runtime protection
NSF/ANSI 61, 372, cULus, CSA, WRAS
Best forWhole-home constant pressure, city mains with varying pressure, multi-fixture homes, kitchen and bath comfort, and installs where noise matters.
Both are self-priming, all-in-one boosters with the same protection suite. The deciding factor is fixed-speed with electronic twin capability (SCALA1) versus variable-speed constant pressure (SCALA2).
SCALA1 wins on range, irrigation control and redundancy — two units pair into an electronic twin booster that alternates duty and stages the second pump in. SCALA2 wins on comfort and municipal duty — true constant pressure, quieter operation, a higher system-pressure rating and a far higher inlet-pressure ceiling.
Parallel twin set 99743075 — shared manifold, pumps run independently
Connectivity
Bluetooth (Grundfos GO), external input
On-unit display and buttons
Starts and stops
25 per hour max
Speed-controlled; 30-minute max runtime timer
Enclosure
Composite, IP X4D
Aluminum + composite, IP X4D
Ports
1 in NPT
1 in NPT, adjustable up to 5°
Certifications
NSF 61/372, CSA, CE
NSF 61/372, cULus, CSA, WRAS, CE
Quick rule. Choose SCALA2 when the goal is steady pressure at the tap all day, quiet operation, or a strong municipal feed — it takes 87 psi of inlet pressure where a SCALA1 5-55 tops out at 29 psi. Choose SCALA1 when you need more head, irrigation or float control, or a coordinated two-pump system with alternation and staging. SCALA2 can share a manifold with a second unit on its own twin set, but the two pumps are not electronically paired.
Rated Performance
Published 60 Hz figures for the U.S. models, plus the pressure each unit adds across its flow range. Use these to confirm your required flow at the required boost sits within the pump’s range with margin.
Specification
SCALA1 3-45
SCALA1 5-55
SCALA2 3-45
Type
Fixed speed
Fixed speed
Variable speed
Max head, 60 Hz
150 ft (65.0 psi)
180 ft (77.9 psi)
147 ft (63.6 psi)
Nominal duty point
15.8 GPM at 82 ft
23.5 GPM at 82 ft
Holds the set point (see curve)
End of plotted curve
21.5 GPM at 47.9 ft
31.2 GPM at 14.9 ft
20.7 GPM at 29.8 ft
Best operating range
11-16 GPM
13-21 GPM
9-16 GPM
Start / set pressure
31.9 psi start
40.6 psi start
43 psi default, 51 psi max set
Max inlet pressure
43.5 psi
29 psi
87 psi
Max system pressure
116 psi
116 psi
145 psi
Motor
0.80 HP (P2)
1.10 HP (P2)
3/4 HP (P1 550 W)
Weight
26.4 lb
30.8 lb
22 lb
Pressure added across the flow range
Every figure below is the pressure the pump adds on top of whatever arrives at its inlet — never the discharge pressure and never the set point. Zero flow is a ceiling, not a working point.
Flow — GPM
0
4.4
8.8
13.2
17.6
22.0
26.4
End of curve
SCALA1 3-45 — psi
64.9
61.6
55.4
46.0
33.9
—
—
20.7 at 21.5 GPM
SCALA1 3-45 — ft
149.9
142.3
127.9
106.2
78.3
—
—
47.9 at 21.5 GPM
SCALA1 5-55 — psi
79.0
75.8
70.5
62.9
52.9
40.5
25.6
6.5 at 31.2 GPM
SCALA1 5-55 — ft
182.5
175.1
162.8
145.2
122.2
93.6
59.2
14.9 at 31.2 GPM
SCALA2 — psi
62.0
58.7
51.0
37.8
22.9
—
—
12.9 at 20.7 GPM
SCALA2 — ft
143.1
135.6
117.7
87.3
52.8
—
—
29.8 at 20.7 GPM
Boost in psi equals head in feet multiplied by 0.433. Figures are read from the published 60 Hz curves in the Grundfos SCALA data booklet 99735562 (07.2026) — curves TM075369 and TM075368 for SCALA1, TM1040350 for SCALA2 — and rounded down where the reading is uncertain. Nothing is extrapolated past the drawn range. The SCALA2 row is the full-speed curve; the seven traces below it on the same chart are the same pump held at lower pressure settings. Grundfos’ printed table gives maximum head as 150 ft (3-45), 180 ft (5-55) and 147 ft (SCALA2); the plotted curves read 150, 182 and 143 ft at zero flow, and the table above prints the curve. Best operating ranges are derived by us from the published head and input-power curves — wire-to-water efficiency peaks near 31 percent on the 3-45, 34 percent on the 5-55 and 39 percent on the SCALA2 — and are not stated by Grundfos. Request the manufacturer submittal for any duty point you need to certify.
Sizing & Best Practices
How we size a SCALA, and what to check before you install one. Send us your numbers and we will run this for you.
Run the numbers yourself
Two calculators do the arithmetic below. The booster sizing calculator turns fixture count, floors and inlet pressure into the flow and boost you actually need, then checks a chosen pump against them. The pressure tank sizing calculator sizes the vessel — needed on any external-tank installation, and needed for the thermal expansion tank at a storage water heater whether or not the booster has one built in.
Required boost equals the pressure you want at the highest fixture, plus 0.433 psi for every foot of elevation from the pump to that fixture, plus friction loss in the piping, minus the pressure already available at the pump inlet. A two-story home wanting 50 psi upstairs, with the pump in the garage 20 ft below and 25 psi at the meter, needs roughly 50 + (20 × 0.433) + friction − 25 ≈ 34 psi of boost plus pipe losses. Read that figure across the pressure-added table above: 34 psi lands a 3-45 near 17 GPM and a 5-55 near 20 GPM.
2. Estimate peak flow honestly
Size flow to simultaneous demand, not the sum of every fixture. For homes, a water-supply-fixture-unit method (IPC Table 604.3 / Hunter’s curve) converts fixture counts into a realistic peak GPM; for light commercial, the IAPMO Water Demand Calculator is more accurate. A single bath rarely exceeds 8-10 GPM at once; a large home with several baths running is typically 14-22 GPM — squarely in the SCALA band. The booster sizing calculator runs the fixture-unit method for you.
3. Check inlet pressure limits
Confirm your static inlet pressure stays under the model limit — 43.5 psi on the SCALA1 3-45 and only 29 psi on the 5-55. This is the check that rules a model out before any curve matters, and on a strong municipal main it rules out the 5-55 first. SCALA2 takes 87 psi, which is why it suits mains that run high. Where the main exceeds the limit, a pressure-reducing valve upstream protects the pump. On a suction lift, both systems self-prime from up to 26 ft, but longer or higher lifts reduce available flow.
4. Size the tank, even on an all-in-one
Both SCALA systems carry an integrated vessel, so no external pressure tank is required for a normal installation. Two cases still need a tank sized: a system with storage ahead of the pump, and — on any system with a storage water heater — the thermal expansion tank at the heater, which is a code requirement independent of the booster. Size either with the pressure tank sizing calculator.
Sizing rule of thumb. If your required flow at the required boost lands past 70 percent of a model’s maximum head, step up a model — SCALA1 3-45 to 5-55, or SCALA1 to SCALA2 for constant pressure. Leaving headroom keeps the pump inside its best operating range — 11-16 GPM on the 3-45, 13-21 GPM on the 5-55, 9-16 GPM on the SCALA2 — which is where it turns the most electricity into water pressure and runs quietest.
Which SCALA Do You Need?
A selection guide by application. Flow figures assume typical fixture-unit demand; call us with your fixture count and elevation for an engineering-led selection.
Application
Typical demand
Recommended
Notes
1-2 bath home, one story
8-14 GPM at 30-45 psi boost
SCALA2 3-45 or SCALA1 3-45
SCALA2 for quiet constant pressure; SCALA1 3-45 where more head is wanted.
3-4 bath home, two story
14-22 GPM at 40-55 psi boost
SCALA1 5-55
The 5-55 holds 52.9 psi at 17.6 GPM where the SCALA2 set point tops out at 51 psi.
Whole-home constant pressure
Variable, under 51 psi boost
SCALA2 3-45
VFD holds the set point across changing demand at under 44 dB(A).
City main running high
10-20 GPM
SCALA2 3-45
87 psi inlet limit against 29-43.5 psi on SCALA1; 145 psi system rating.
Roof / storage / break tank
10-22 GPM
SCALA1 or SCALA2
Self-priming to 26 ft from an atmospheric tank. Size storage with the tank calculator.
Shallow well (to 26 ft)
10-20 GPM
SCALA1 3-45 or 5-55
Self-priming with dry-run protection; add the 250-micron inlet filter.
Irrigation / water transfer
15-22 GPM
SCALA1 5-55
External input and fixed speed move water A-to-B on demand.
Standby / higher peak flow
To 49 GPM (3-45 pair) or 65 GPM (5-55 pair)
SCALA1 Twin
Two SCALA1 on the twin set alternate duty and stage in. Published twin curves.
Highest head required
Any
SCALA1 5-55
180 ft against 150 ft on the 3-45 and 147 ft on the SCALA2.
What Makes SCALA Different
The engineering shared across the line, and why it matters on an installation.
All-in-one, self-priming
Pump, motor, small vessel and check valve in one enclosure that primes from dry to 26 ft of suction lift — draw from a tank, cistern or shallow well without a separate lift pump or external tank.
Constant pressure (SCALA2)
The inverter varies motor speed to hold your set point as demand changes, instead of cycling against a pressure switch. Steady pressure at the tap, soft start and stop, and no water hammer.
Electronic twin (SCALA1)
Two SCALA1 units pair on the twin set 99725168 and communicate over a cable, alternating duty by runtime or number of starts and staging the second pump in when demand rises — standby redundancy without a custom panel. SCALA2 has its own parallel twin set, 99743075, which shares the manifold but not the control.
Two pumps hold more pressure
Each pump in a twin carries half the water, so each sits higher on its own curve. Grundfos publishes both cases: on the 3-45, 22 GPM is 17.5 psi added from one pump and 46.7 psi from the pair. The shut-off ceiling at zero flow is the one figure that does not rise.
Water-cooled, quiet
Cooling by the pumped liquid eliminates the fan. SCALA2 runs under 44 dB(A) and both units install in a closet or recess with limited air movement — SCALA1 is rated to 131°F ambient, SCALA2 on U.S. 60 Hz supply to 113°F.
Full protection suite
Dry-running protection, anti-cycling and micro-leakage detection, an adjustable maximum-runtime timer, and current- and temperature-dependent motor protection with automatic restart — no external motor protection needed.
Bluetooth & external input (SCALA1)
Configure and monitor over Grundfos GO with Bluetooth built into the pump, and wire an external input for a float switch or irrigation calendar — useful for tank filling and scheduled watering.
Drinking-water certified
Both systems are certified to NSF/ANSI 61 and NSF/ANSI 372 low-lead for potable contact, with CSA electrical listing; SCALA2 adds cULus and WRAS. Both carry IP X4D for outdoor installation.
See SCALA In Action
Two minutes each: how a SCALA2 installs, and how two SCALA1 units become a twin booster. Full installation and service video libraries are on each product page.
We sell booster pumps from every major line, so we can be straight about where SCALA fits. Start in-family: Grundfos CMBE is the step up when a job outgrows SCALA. Below that, most residential VFD boosters compare most directly with SCALA2; SCALA1 is the fixed-speed, twin-capable alternative. All hydraulic figures are single-unit.
Grundfos SCALA vs Grundfos CMBE
Specification
SCALA1
SCALA2
CMBE
Control
Fixed speed
Variable speed
Variable speed
Flow
15.8-23.5 GPM nominal
to 20.7 GPM
to 70 GPM
Max head
150-180 ft
147 ft
to 365 ft
Models
2
1
10 (+3 TWIN systems)
Self-priming
26 ft
26 ft
No — max 3.3 ft lift
Max system pressure
116 psi
145 psi
145 psi
Hydraulics
Composite
Aluminum + composite
Stainless AISI 304
Noise
< 55 dB(A)
< 44 dB(A)
55 dB(A)
Multi-pump
Electronic twin
Parallel twin set
TWIN with cascade control & alternation
Typical use
Home, irrigation, transfer
Whole-home comfort
Whole building, light commercial
CMBE is the Grundfos step up from SCALA: a stainless packaged booster line reaching roughly three times the flow and twice the head, with a true cascade-controlled twin for buildings. The trade: CMBE is not self-priming — Grundfos allows a maximum 1 m (3.3 ft) suction lift including inlet pipe loss — so tank draws and shallow wells stay with SCALA, and SCALA2 is the quieter unit. View the CMBE line →
Grundfos SCALA vs DAB Esybox
Specification
SCALA2
DAB Esybox Mini 3
DAB Esybox
Control
Variable speed
Variable speed
Variable speed
Max flow
to 20.7 GPM
22 GPM
31.7 GPM
Max head
147 ft
183 ft
213 ft
Motor
3/4 HP
1.1 HP
2.1 HP
Voltage
115 / 230 V
115 / 230 V (one unit)
230 V
Max system pressure
145 psi
108 psi
116 psi
Noise
< 44 dB(A)
Quiet
~43 dB(A)
Self-priming
26 ft
26 ft
26 ft
Multi-pump
Parallel twin set
Wireless pairing
Wireless to 4
Certifications
NSF 61/372, cULus, WRAS
NSF 61/372, UL, CSA
NSF 61/372, UL, CSA
Esybox offers more flow and head per unit and wireless multi-pump grouping that SCALA2 cannot match. SCALA2 counters with a higher system-pressure rating and an 87 psi inlet ceiling. For higher flow or a commercial station, step to DAB Esybox or Esybox Max.
Grundfos SCALA vs A.Y. McDonald DuraMAC
Specification
SCALA1
SCALA2
DuraMAC Residential
DuraMAC VS
Control
Fixed speed
Variable speed
Fixed speed
Variable speed
Flow
15.8-23.5 GPM nominal
to 20.7 GPM
20 GPM
6-35 GPM
Boost / head
150-180 ft
147 ft
35-70 psi
25-65 psi
Motor
0.8-1.1 HP (P2)
3/4 HP (P1)
1/2-1 HP
1-2 HP
Max system pressure
116 psi
145 psi
—
120 psi
Construction
Composite
Al + composite
Stainless components
SS 304/316
Self-priming
26 ft
26 ft
Yes
Yes
Certifications
NSF 61/372
NSF 61/372
NSF 61
NSF 61, UL
Origin
Denmark/Serbia
Denmark/Serbia
Made in USA
Made in USA
DuraMAC VS offers more flow and full stainless-steel hydraulics with domestic manufacture; SCALA2 counters with quieter operation, a higher system-pressure rating and NSF 372. SCALA1 and DuraMAC Residential are the fixed-speed options in each line.
Grundfos SCALA vs Goulds Water Technology
Specification
SCALA2
Goulds ResiBoost
Goulds Aquavar
Control
Variable speed
Variable speed (VSD)
Variable speed (e-AB3 / e-AB2)
Max flow
to 20.7 GPM
to 35 GPM
to 80 GPM (e-AB2)
Motor
3/4 HP
0.75-2 HP
0.5-5 HP
Pump / motor
Al + composite
Stainless e-HM
IE5 Smart Motor / e-HM
Self-priming
26 ft
Not self-priming
Not self-priming
Integrated tank
Yes
Yes (packed separate)
Yes (kit)
Install rating
IP X4D outdoor
Indoor
NEMA 1 / NEMA 3R
Certifications
NSF 61/372, cULus, WRAS
NSF 61/372 (Xylem)
NSF 61/372 (Xylem)
Goulds ResiBoost and Aquavar scale to higher flow and horsepower with stainless e-HM hydraulics, and Aquavar reaches commercial duty with an outdoor-rated enclosure. SCALA2 is the more compact, self-priming, plug-and-pump choice for single-residence constant pressure.
Grundfos SCALA vs Davey
Specification
SCALA2
Davey DynaDrive
Davey EvoDrive
Control
Variable speed
Variable speed
Variable speed (PM motor)
Max flow
to 20.7 GPM
12-24 GPM tabulated
28 GPM
Max set pressure
51 psi
87 psi on all three models
up to 95 psi
Max casing pressure
145 psi
116-145 psi
145 psi
Self-priming lift
26 ft
Flooded / limited
13 ft
Construction
Al + composite
304 stainless
304 stainless
Multi-pump
Parallel twin set
Daisy-chain 2 pumps
Duty/standby (2 pumps)
Certifications
NSF 61/372
NSF 61 (WQA)
NSF-oriented
Davey DynaDrive and EvoDrive offer stainless hydraulics, dual-pump modes and a far higher settable pressure — 87 to 95 psi against 51 psi on the SCALA2, which matters on tall buildings. SCALA2 counters with greater self-priming lift (26 ft against 13 ft on EvoDrive) and NSF 372 low-lead certification.
Grundfos SCALA vs Franklin Electric
Specification
SCALA2
FE VersaBoost Pro
FE MH Series
Type
VFD constant pressure
VFD constant pressure
Multi-stage (bare pump)
Max flow
to 20.7 GPM
18-25 GPM
15 / 30 / 45 GPM nominal
Motor
3/4 HP
0.8-1.1 HP
1-2 HP
Self-priming
26 ft
No (submersible-based)
No
Integrated tank / CV
Yes
Yes
No (external drive/tank)
Noise
< 44 dB(A)
45 dB(A)
—
Install rating
IP X4D outdoor
NEMA 3R
Indoor/outdoor motor
Certifications
NSF 61/372, cULus, WRAS
NSF 61/372, UL, CSA
NSF 372, UL, CSA
VersaBoost Pro is the closest Franklin match to SCALA2 — a comparable all-in-one VFD system built on an encapsulated submersible motor, with an outdoor-rated NEMA 3R enclosure, though not self-priming. MH Series is a bare multistage pump for building a custom booster and runs fluid to 225°F, far beyond the SCALA class. For duplex/triplex commercial stations, Franklin’s Inline SpecPAK sits above the SCALA class.
SCALA Accessories
Factory accessories that complete a SCALA installation. Order with the pump so the job arrives together — product pages linked as they publish.
Inlet Filter
250-micron 1 in NPT filter (99725185) that protects the pump from sand and debris on well and tank feeds.
Twin Accessory Set
Base plate, inlet/outlet manifolds with brass isolating valves and fixing screws. SCALA1 set 99725168 includes the communication cable; SCALA2 set 99743075 does not.
Flexible Hose Set
WRAS-approved braided connection hoses for vibration isolation and easy service.
Pump Stand
Expanded-polypropylene stand that supports the pump, cuts vibration and noise, and limits the effect of condensation and minor pipe leakage.
Locking Pin (SCALA2)
Stops the clicking noise under positive inlet pressure; remove to restore self-priming.
Genuine Grundfos spare parts and service kits are available by model; contact us with the pump type and serial for the correct part.
Why Source Grundfos SCALA from Watermain Supply
The Right US Build
SCALA1 and SCALA2 in U.S. 60 Hz configurations, with NPT connections and the plug that matches your service — 115 V NEMA 5-15 or 230 V NEMA 6-15.
Engineering-Led Sizing
We size from fixture count, elevation, inlet pressure and pipe friction against the manufacturer curve — and tell you when a smaller model will do.
Multi-Brand Perspective
We also sell DAB, A.Y. McDonald DuraMAC, Goulds, Davey and Franklin Electric. If SCALA is not the right fit, we will say so and quote the one that is.
Twin & Standby Design
Guidance on SCALA1 twin boosters for standby redundancy or higher peak flow, with the right accessory set and controls.
Account Terms Available
Net-30 terms for qualified contractor, property-management and municipal accounts, handled in-house.
Parts & Aftermarket
Genuine Grundfos accessories and service parts with model cross-reference, so you get the right kit the first time.
Frequently Asked Questions
Common questions from homeowners, plumbers and engineers selecting a Grundfos SCALA booster.
What is the difference between SCALA1 and SCALA2?
SCALA1 is a fixed-speed booster available in two models (3-45 and 5-55), with Bluetooth, an external input for float or irrigation control, and the ability to pair two units into an electronic twin booster with alternation and staging. SCALA2 is a single-model variable-speed unit that holds constant pressure at every tap, runs quieter at under 44 dB(A), and takes up to 87 psi of inlet pressure against 29-43.5 psi on SCALA1. Choose SCALA2 for steady whole-home pressure or a strong main, SCALA1 for more head, irrigation control or twin redundancy.
Do I need a separate pressure tank with a SCALA?
No. Both systems include an integrated vessel and check valve. SCALA2 has a diaphragm tank sized for its VFD control logic, and SCALA1 has a small vessel with anti-cycling logic. An external tank is not required for normal installations — but a thermal expansion tank is still required at any storage water heater, and you can size it with the pressure tank sizing calculator.
Can a SCALA run on both 115 V and 230 V?
Each variant ships for a specific supply: 115 V uses a NEMA 5-15 plug, 230 V a NEMA 6-15 plug. Select the voltage that matches your service when ordering. Both are single-phase, 60 Hz, and neither is field-convertible.
How much boost does a SCALA provide?
Head in feet converts to pressure at 0.433 psi per foot, and every figure is what the pump adds on top of the inlet. Grundfos states a maximum head of 150 ft (about 65 psi) on the SCALA1 3-45 and 180 ft (about 78 psi) on the 5-55. SCALA2 holds an adjustable set point with a 51 psi ceiling, from a curve that reaches 147 ft. Available boost falls as flow rises — see the pressure-added table above and size with margin.
What is the maximum inlet pressure?
It is model-specific and it is the limit that rules a selection out before any curve matters. SCALA1 3-45 takes 43.5 psi and the 5-55 only 29 psi; SCALA2 takes 87 psi. On a strong municipal main, check this figure first and fit a pressure-reducing valve upstream if the main runs above it.
Can a SCALA draw water from a tank or shallow well?
Yes. Both SCALA1 and SCALA2 are self-priming to 26 ft of suction lift, so they can pull from an atmospheric storage tank, cistern or shallow well. We recommend the 250-micron inlet filter on well and tank feeds to protect the pump.
Can I run two SCALA pumps together?
SCALA1 is twin-capable: two units mount on the twin accessory set 99725168, communicate over a cable, and alternate duty by runtime or number of starts, staging the second pump in as demand rises. Two pumps also hold more pressure at the flow the building actually draws — Grundfos publishes both cases, and on the 3-45, 22 GPM is 17.5 psi added from one pump and 46.7 psi from the pair. SCALA2 has its own parallel twin set, 99743075, which supplies the base plate, manifolds and valves so two units can share one installation; the communication cable is SCALA1-only, so each SCALA2 keeps its own set point.
How do I size a SCALA for my house?
Required boost is target pressure at the highest fixture, plus 0.433 psi per foot of elevation, plus friction, minus what already arrives at the inlet. Peak flow comes from a fixture-unit method rather than adding every fixture together. The booster sizing calculator runs both and checks a chosen model against the result, or call 1-888.510.4036 and we will size it with you.
Is SCALA certified for drinking water?
Yes. Both systems are certified to NSF/ANSI 61 for drinking-water system components and NSF/ANSI 372 for low lead content. SCALA1 carries CSA and CE; SCALA2 additionally carries cULus and WRAS.
Can I install a SCALA outdoors?
Both carry an IP X4D rating suitable for outdoor installation; mount on the pump stand to keep ventilation clear of standing water and provide freeze protection in cold climates. Ambient limits are 131°F on SCALA1 and 113°F on the U.S. 60 Hz SCALA2.
Ready to Size Your Booster?
Send us your fixture count, number of floors, inlet pressure and required flow. We will respond with a sized SCALA selection, the accessories you need, and lead time.
Technical data on this page is taken from the Grundfos SCALA Data Booklet 99735562 (07.2026), U.S. 60 Hz, and is subject to change by the manufacturer. Confirm against the current installation manual and pump curve before specifying.
Grundfos, SCALA, SCALA1, SCALA2 and Grundfos GO are trademarks of Grundfos Holding A/S, used here for product identification only. DAB, Esybox, DuraMAC, Goulds, ResiBoost, Aquavar, Davey, DynaDrive, EvoDrive, Franklin Electric, VersaBoost and SpecPAK are trademarks of their respective owners, used here for product identification only.
Watermain Supply is a DBA of E4 Industrial LLC, an independent industrial supplier based in Houston, Texas.
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