What should the pressure be on a Vaillant ecoTEC?
The pressure on a Vaillant ecoTEC should be at least 1 bar, and around 1.5 bar is ideal. Those are the figures in the ecoTEC plus operating instructions, which describe 1.5 bar as a good standard value and give 2.5 bar as the maximum. The same instructions tell you to top up the heating water once the pressure is lower than 0.8 bar.
Vaillant adds one detail other brands rarely mention: for each metre of height in the heating installation, add 0.1 bar to the minimum. In a tall house, or where the boiler is on the ground floor and radiators run up two or three storeys, your installer may have set the system a little higher than 1 bar for that reason. If they left a note of the fill pressure with the boiler paperwork, use that figure.
The ecoTEC pro operating instructions give a recommended range of 1 to 2 bar and use the same 0.8 bar point to prompt a top-up. For how Vaillant compares with other makes, and what the reading means hot and cold, see our guide to normal boiler pressure.
How the ecoTEC shows the pressure
Most ecoTEC boilers have no dial gauge. The pressure is read by a sensor and shown on the display, and the way it appears depends on the model.
ecoTEC plus
The ecoTEC plus operating instructions list three places to see the pressure:
- As a number at the bottom right of the basic display.
- As a symbol of five stepped bars along the top edge of the display. More bars filled means higher pressure.
- In the menu, under MAIN MENU, then INFORMATION, then Water pressure.
ecoTEC pro
The ecoTEC pro shows the pressure as a bar graph with two dashed lines marking the permitted range. When the pressure moves outside that range, the symbol flashes. The display switches between the fault message and the current pressure if the pressure has fallen too far.
Older ecoTEC models
Some older ecoTEC boilers and some installations also have a separate dial gauge, either on the boiler or near the filling point. If you have both and they disagree noticeably, one of them may be faulty, so ask an engineer to check the real pressure with a test gauge.
Vaillant pressure figures by model
| Model | Where the pressure shows | Recommended | Top up below | Boiler stops |
|---|---|---|---|---|
| ecoTEC plus combi and system | Number at bottom right, five bar symbol, information menu | At least 1 bar, 1.5 bar ideal, 2.5 bar maximum | 0.8 bar | About 0.5 bar, with F.22 |
| ecoTEC pro combi | Bar graph between two dashed lines, flashes when out of range | 1 to 2 bar | 0.8 bar | Below 0.5 bar, with F.22 |
| Older ecoTEC models | Display, and on some installations a dial gauge | Check your user manual | Check your user manual | F.22 or F22 |
The 0.5 bar cut-out figure comes from the ecoTEC plus installation and maintenance instructions and the ecoTEC pro operating instructions. Check the operating instructions for your exact boiler, which Vaillant publishes on its website by model name.
F22 and other signs of low pressure on a Vaillant
When the pressure falls too low, an ecoTEC shows F.22, which Vaillant describes as no or insufficient water in the product, or water pressure too low. The boiler shuts down to protect itself. The ecoTEC plus operating instructions say the F.22 message goes out and the boiler works again on its own once the pressure is back up to the required level. Our Vaillant F22 page covers the code itself.
If the display shows a sensible pressure but the boiler still reports a pressure or circulation problem, the sensor or pump may be at fault rather than the water level. That is covered on our Vaillant F75 page.
Where is the filling loop on a Vaillant?
On a Vaillant ecoTEC combi, the filling loop connects underneath the boiler, between the cold water isolation valve and the heating circuit. The ecoTEC plus installation instructions describe a filling line with a double non-return valve that the installer clips onto the cold water isolation valve with a spring clip. It is a temporary connection: after filling, the double non-return valve is taken off the cold water valve again.
On an ecoTEC system boiler with a separate hot water cylinder, there is no cold mains inside the boiler, so the installer fits a separate filling point on the pipework. Vaillant's instructions simply say to open the filling cock as shown by your installer. It is often under the boiler or near the cylinder in the airing cupboard.
If you cannot see a hose or loop, it may have been stored with the paperwork. Our filling loop guide shows what each type looks like and why it must not stay connected.
How do I repressurise my Vaillant boiler?
To repressurise a Vaillant boiler, connect the filling line, open the valves slowly and fill until the display reads about 1.5 bar, then close and disconnect it. The steps below follow the ecoTEC plus operating instructions for combi models.
- Let the system cool. Turn the heating off and wait until the radiators are cool, so you read a true cold pressure.
- Open all radiator valves. Vaillant lists this as the first step, so water can reach every radiator.
- Connect the filling line. Fit the double non-return valve onto the cold water isolation valve under the boiler and secure it with the spring clip, if it is not already connected.
- Open the valves slowly. Open the isolation valves so water flows into the heating system, and watch the pressure number or bar symbol on the display.
- Stop at the target. Close the valves when the display reads about 1.5 bar, or the figure your installer gave you.
- Disconnect the filling line. Take the double non-return valve off the cold water valve, catching any drips.
- Check again. If a radiator needs bleeding, bleed it and top up again if the pressure falls. Our guide to bleeding a radiator shows how.
On a system boiler, open the filling cock or loop your installer showed you, fill slowly to the same figure, then close it fully.
Fill slowly and watch the display the whole time. The pressure can jump quickly once the loop is fully open, and it is easier to add a little more than to let water back out.
Vaillant boiler pressure too high
A Vaillant boiler pressure above 2.5 bar is too high, because that is the maximum in the ecoTEC plus operating instructions. If you overfilled it, bleeding a radiator brings it down. Check that the filling valves are fully shut, because a valve that still passes water will push the pressure back up.
If the cold reading is fine but the pressure climbs close to 3 bar each time the heating runs, the expansion vessel is the usual suspect. Our guide to boiler pressure that is too high explains the causes and what an engineer will check.
Why the kind of water matters
Vaillant's operating instructions warn you to fill only with suitable heating water, because unsuitable water can damage seals, block components and cause noise. For a normal top-up from the filling loop this is not a problem. It does become one if you top up every week, because each top-up adds fresh mains water and dilutes the inhibitor your installer added. That is another reason to find the cause of a pressure drop rather than living with it. Our guide to a boiler losing pressure shows where to look.
When to call a Gas Safe registered engineer
Book a Gas Safe registered engineer, or contact Vaillant through its website, if:
- The pressure falls below 0.8 bar again soon after you topped it up.
- F.22 comes back even though the display showed a normal pressure after filling.
- The pressure goes above 2.5 bar when the heating runs.
- You cannot find a filling point, or the valves will not turn.
Only use the filling loop and valves outside the boiler case. The pressure sensor, pump and expansion vessel sit inside, next to gas and electrical parts, and only a Gas Safe registered engineer should work on them.
When you call, give the engineer the pressure shown on the display when cold and when hot, any codes you have seen and how often you have topped up.