How often should I check the SCALA2 tank pre-charge?

Grundfos recommends checking the tank pre-charge once a year to maintain correct pressure and prevent issues such as noise, pressure fluctuations, increased risk of failures, and higher energy consumption.

Grundfos SCALA2: Pressure Tank Pre-charge | Official Guide 2026

Official Grundfos Guide 2026

Grundfos SCALA2: Optimal Performance and Efficiency with Pressure Tank Pre-charge

How to adjust the integrated pressure tank pre-charge in 3 simple steps, when to do it, and the recommended pressure table from Grundfos.

🔧 3 simple steps 📅 Annual check recommended 📊 Official pressure table 🎓 Free Ecademy course

The Grundfos SCALA2 features an integrated pressure tank that eliminates the need for an external tank, simplifying installation. But for the system to perform at its best, the tank pre-charge must be correctly adjusted during installation and checked once a year. In this guide, you'll find the official 3-step procedure, the Grundfos-recommended pressure table, and everything you need to ensure perfect water pressure, low noise, and minimal energy consumption.

Why Pre-charge Is Critical for SCALA2 Performance
When to Adjust and Check Pre-charge
Official Grundfos Video: Pre-charge in 3 Steps
How to Pre-charge the Pressure Tank Step by Step
Optimal Pre-charge Pressure Table (bar and psi)
How to Install the SCALA2 Pump Correctly
Free Grundfos Ecademy Training — Course 40: SCALA2
Frequently Asked Questions About SCALA2 Pre-charge

1Why Pre-charge Is Critical for SCALA2 Performance

The Grundfos SCALA2 is a domestic water booster pump with an integrated pressure tank. Unlike other booster pumps, it incorporates the tank directly into the pump body, greatly simplifying installation. But all pressure systems with air expansion tanks require adequate pre-charge pressure to operate optimally.

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What happens if pre-charge is incorrect?

If adequate pre-charge pressure is not maintained in the SCALA2's integrated tank, serious issues can arise that affect comfort and the pump's lifespan.

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Symptoms of Incorrect Pre-charge

Noisy pump operation
Pressure fluctuations and oscillations
Pump starts and stops continuously (short-cycling)
Increased risk of damage to internal components
Significantly higher energy consumption
Reduced lifespan of tank and membrane

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Benefits of Correct Pre-charge

Constant and stable water pressure
Quiet operation
Fewer motor start-ups
Optimal energy consumption
Maximum lifespan for all components
Perfect comfort at all household taps

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The 70% Rule: Grundfos' Key Formula

Grundfos establishes a clear and simple rule for calculating the correct pre-charge pressure of the SCALA2's integrated tank:

Pre-charge Pressure = 70% of Set Point Example: Set point 3.0 bar → Pre-charge = 2.1 bar (30 psi)
Pre-charge must never exceed 70% of the set point

📋 Factory values: The SCALA2 is supplied with a default pre-charge pressure of 1.8 bar (26 psi) for transport regulations, and a default set point of 3 bar (44 psi) — the optimal discharge pressure for most homes. The correct pre-charge pressure must be adjusted to the set point during installation.

2When to Adjust and Check Pre-charge

Grundfos specifies two situations in which the SCALA2 tank pre-charge pressure should be adjusted or verified:

During initial installation: The SCALA2 arrives from the factory with 1.8 bar pre-charge for transport regulations. It must be adjusted to 70% of the set point configured during commissioning.
Once a year: Grundfos recommends an annual check to ensure pressure hasn't dropped due to natural air loss over time.

⚠️ Default set point = 3 bar: If the pump's set point hasn't been changed, the correct pre-charge is 2.1 bar (30 psi). If you've configured a different set point, consult the table in Section 5 to find the corresponding optimal pre-charge.

3Official Grundfos Video: Tank Pre-charge in 3 Steps

Grundfos has published an official video of 3 minutes and 48 seconds showing the complete procedure for pre-charging the integrated pressure tank of the SCALA2. We recommend watching it before performing the process for the first time:

How to Pre-charge the Pressure in the Integrated Pressure Tank of the SCALA2 System

Official Grundfos Video · 3 min 48 sec

✔️ If the video doesn't load, you can access it directly via grundfos.com by searching for "SCALA2 precharge pressure tank".

4How to Pre-charge the Pressure Tank Step by Step

The process of how to pre-charge the SCALA2 pressure tank consists of three steps that can be completed in under 10 minutes with the right tools. You'll need a pressure gauge and a hand pump for inflation.

Stop the system and depressurize it

Stop the SCALA2 by pressing the stop button. To depressurize the system, close the supply pipe and open a tap to release residual system pressure. Alternatively, you can disconnect the pump from the pipes.

⚠️ It is essential that the system is completely depressurized before adjusting the tank pre-charge. If there is pressure in the circuit, the tank measurement will be incorrect.

Adjust the air pressure in the tank

Unscrew the cap of the pressure tank air valve. You can use a screwdriver to loosen it, but generally hand-tightening is sufficient. Pump air until reaching the required pressure: 70% of the set point, never above. Consult the table in Section 5 to find the exact value corresponding to your set point. Replace the air valve cap and tighten it securely so air cannot escape over time.

📋 Practical example: If the set point is 3.0 bar (default value), the correct pre-charge is 2.1 bar (30 psi). If you have a set point of 2.5 bar, the pre-charge should be 1.8 bar (26 psi).

Open the supply valve and restart the SCALA2

Open the supply shut-off valve and restart the SCALA2. The system will resume operation with the newly configured pre-charge pressure. Check for leaks and ensure pressure is stable.

✔️ Once the process is complete, the SCALA2 should operate quietly and provide constant water pressure without noticeable fluctuations.

✔️ Professional tip: Note the date when you performed the check. Grundfos recommends repeating it annually to maintain optimal system performance.

5Optimal Pre-charge Pressure Table (bar and psi)

Grundfos provides the official table for optimal adjustment of the SCALA2 tank pre-charge pressure for each possible set point. Remember: pre-charge must always be 70% of the set point and never above.

Optimal Pre-charge Pressure Adjustment for Tank — SCALA2

Pre-charge = 70% of set point / desired discharge pressure. Source: Official Grundfos.

Set Point bar (psi)	Optimal Tank Pre-charge bar (psi)
5.5 (80)	3.9 (57) *
5.0 (73)	3.5 (51) *
4.5 (65)	3.2 (46) *
4.0 (58)	2.8 (41)
3.5 (51)	2.5 (36)
3.0 (44) ⭐ Default	2.1 (30)
2.5 (36)	1.8 (26)
2.0 (29)	1.4 (20)
1.5 (22)	1.1 (16)

* Ensure that the available inlet supply pressure at your installation is sufficient to reach these higher set points. · ⭐ The 3.0 bar set point is the factory default value, suitable for most homes. · The SCALA2 is supplied with a pre-charge of 1.8 bar (26 psi) for transport regulations: it must be adjusted during installation.

📋 For most homes: The default set point of 3.0 bar (44 psi) is appropriate. This means the tank pre-charge should be 2.1 bar (30 psi). If the SCALA2 was recently installed and pre-charge wasn't adjusted, the factory value (1.8 bar) is likely incorrect for your actual set point.

6How to Install the SCALA2 Pump Correctly

The SCALA2 pump installation follows a structured process. Grundfos recommends reading the quick guide included in the box and consulting the information on the back of the packaging before starting. Here's the complete step-by-step process:

Preparation and Floor Mounting

Mark and drill holes at the chosen location for the pump.
Insert expansion anchors into the holes.
Place the noise-reducing mat (included): although the SCALA2 is already very quiet, the mat further reduces vibrations and noise.
Position the pump on the mat and secure it to the floor with the four screws.
Ensure there is a nearby drain to protect the SCALA2 from water that could damage electrical components.

Hydraulic Connection

Remove the two connectors by unscrewing them by hand.
Mount the two flexible hoses onto each connector and tighten with a wrench.
Reattach the connectors to the pump, again by hand only.
Connect the two flexible hoses to the pipes and tighten with a wrench.
If the water contains particles or solids, install an inlet particle filter at this point.

Pump Priming

Remove the priming plug (you can use a screwdriver to loosen it, but usually hand-tightening is sufficient).
Pour 1.7 liters (0.45 gallons) of water into the priming hole.
Insert and tighten the priming plug, again by hand.

Startup and Pressure Adjustment

Open the shut-off valves and close the bypass valve to allow flow through the pump.
Locate the tap farthest from the pump and open it fully.
Connect the SCALA2 and turn on the switch.
Adjust the pressure by pressing the arrows on the pump display until the farthest tap delivers the desired water pressure.

⚠️ Critical step after installation: Once the pressure (set point) is configured, you must pre-charge the integrated pressure tank to 70% of this value. The SCALA2 arrives from the factory with 1.8 bar pre-charge for transport regulations, but it must be adjusted to the correct value for the chosen set point. Consult the table in Section 5.

✔️ Once installation and tank pre-charge are correctly completed, the SCALA2 provides perfect water pressure, low noise levels, low energy consumption, and maximum comfort for years to come.

7Free Grundfos Ecademy Training — Course 40: SCALA2

Grundfos offers a free 3-module, 15-minute training course on its Grundfos Ecademy platform, specifically dedicated to the SCALA2 pump. The course covers applications, installation, and the concept of perfect water pressure, and is part of the Domestic Pumps training pathway.

Grundfos Ecademy — Course 40: SCALA2 Water Pressure Booster Pump

Discover the applications and advantages of the SCALA2 water pressure booster pump, including the concept of perfect water pressure.

3 Modules ⏱ 15 minutes 📗 Basic 🆓 Free ★★★★★ 5.0 (9 ratings)

Official course content from the Grundfos Ecademy platform. Part of the training pathway — Domestic Pumps:

SCALA2 Features and Advantages A quick analysis of the applications, features, and advantages of the SCALA2. ⏱ 3 min 45 sec
Perfect Water Pressure Discover all the advantages of perfect water pressure and how it can enhance comfort and well-being for household users. ⏱ 3 min 30 sec
How to Install a Grundfos SCALA2 Pump Learn to install the SCALA2 water booster pump as we guide you step by step through a simple process. ⏱ 3 min 48 sec

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Test your knowledge: Upon completing the 3 modules, the course includes an assessment quiz to verify what you've learned and successfully complete the course.

Start the course on Ecademy → grundfos.com

📋 The course is free for all installers registered at grundfos.com/ecademy. It's part of Grundfos' Domestic Pumps training pathway and is ideal for quickly getting up to speed with the SCALA2.

8Frequently Asked Questions About SCALA2 Pre-charge

What pre-charge pressure should the SCALA2 tank have?

The pre-charge pressure should be 70% of the set point or desired discharge pressure, never above. For the default set point of 3.0 bar, the optimal pre-charge is 2.1 bar (30 psi). Consult the table in Section 5 for any other set point.

How often should I check the tank pre-charge?

Grundfos recommends checking the integrated pressure tank pre-charge once a year. All air expansion tanks lose a small amount of pressure over time, and an annual check ensures the system continues to operate optimally.

What is the factory pre-charge pressure for the SCALA2?

The SCALA2 is supplied with a default pre-charge pressure of 1.8 bar (26 psi) for transport regulations, and a default set point of 3 bar (44 psi). The correct pre-charge for the default set point should be 2.1 bar, so it must be adjusted during installation to ensure optimal operation.

What problems does incorrect pre-charge cause in the SCALA2?

Grundfos warns that inadequate pre-charge can cause: noisy operation, pressure fluctuations, short-cycling (the pump starts and stops continuously), increased risk of damage to internal components, and higher energy consumption.

Must the system be depressurized before adjusting pre-charge?

Yes, it is essential. Grundfos specifies that you must stop the SCALA2, close the supply pipe, and open a tap to release all residual system pressure before adjusting the tank pre-charge. If there is pressure in the circuit, the measurement will be incorrect and the adjustment invalid.

Does the SCALA2 need an external pressure tank?

No. The SCALA2 incorporates the pressure tank directly into the pump body, which simplifies installation and eliminates the need for an external tank. This is one of the SCALA2's distinguishing features compared to other booster pumps on the market.

How much water does the SCALA2 need for initial priming?

The SCALA2 requires 1.7 liters (0.45 gallons) of water for initial priming. Remove the priming plug, pour in the water, and replace the plug tightly (by hand is sufficient) before starting the system.

Does Grundfos offer free training on the SCALA2?

Yes. Grundfos offers Course 40 — SCALA2 Water Pressure Booster Pump on Grundfos Ecademy: 3 modules, 15 minutes, basic level, rated 5/5 stars and completely free for registered installers. It's part of the Domestic Pumps training pathway.

Maintaining the SCALA2 pressure tank pre-charge at the correct value — 70% of the set point — is one of the simplest and most important steps to ensure the pump's optimal long-term performance. About 10 minutes of work once a year makes the difference between a system that works perfectly and one that generates noise, pressure fluctuations, and unnecessary energy consumption.

Remember: the SCALA2 arrives from the factory with a pre-charge of 1.8 bar for transport regulations. It must always be adjusted to the correct value during installation and checked annually. For the default set point of 3 bar, the pre-charge should be 2.1 bar (30 psi).

If you want to deepen your knowledge of SCALA2 installation and features, access Course 40 — SCALA2 on Grundfos Ecademy (free, 15 minutes, 3 modules) or consult all official documentation at grundfos.com.

Font: grundfos.com

Grundfos SCALA2: Pressure Tank Precharge | Official Guide 2026