What fault 1017 means
1017 is the low system pressure code on Worcester's newer Greenstar boilers. It means the sealed heating circuit has lost enough water pressure that the boiler will not run safely, and in most homes the fix is a top-up that takes a few minutes.
Worcester's user instructions for the Greenstar 4000 combi (document 6 720 891 170, 2020) show exactly what you will see: a screen reading "Fault - 1017", a pressure figure such as 0.2 bar, and the message "System pressure too low". The same document says low pressure is indicated when the reading sits between 0 and 0.79 bar in the pressure menu display.
The Greenstar 8000 Life installation and maintenance instructions (document 6720883865) list 1017 in category W of the fault code table as "System pressure too low". The 2019 edition of that manual uses the wording "Water pressure too low". Same code, same meaning.
Which Greenstar boilers show 1017
| Boiler | Worcester document | Wording for 1017 |
|---|---|---|
| Greenstar 4000 GR4700iW 25 C and 30 C | User instructions 6 720 891 170 (2020) | "System pressure too low" |
| Greenstar 8000 Life GR8300iW C | Installation and maintenance 6720883865 (2019) | "Water pressure too low" |
| Greenstar 8000 Life GR8300iW 30 to 50 C | Installation and maintenance 6720883865 (2021) | "System pressure too low", category W |
Older Greenstar i boilers report the same problem differently. If your display shows two characters followed by a number, see our page on Worcester CE 207, which is the older equivalent.
What pressure the 4000 instructions treat as normal
The Greenstar 4000 user instructions separate two readings, and knowing which one you are looking at avoids overfilling.
- Static pressure is measured when the boiler is cold and has not fired. Worcester says this will generally be 0.8 to 1.7 bar.
- Operating pressure is measured while the boiler is firing for heating or hot water, and will generally be 1 to 2 bar.
- The instructions say to recharge the system if the indicator reads less than 0.8 bar.
- The pressure display uses colour zones: red means too low or too high, yellow means low or slightly high, and green means normal.
The basic checks at the back of the same document ask whether the cold pressure is between 1 and 1.5 bar, and Worcester notes that your installer will advise the best operating pressure for your system. If in doubt, aim for the middle of the green zone with the boiler cold.
Clearing 1017: the short version
Top up with the boiler cold, using the filling link, and watch the display while you do it. On the Greenstar 4000, the screen changes to a "System pressure ok" message telling you to stop refilling. Our Worcester boiler pressure guide walks through the filling link step by step for each range, so we will not repeat it here.
If the fault message stays after the pressure is back in range, the 4000 instructions explain the reset: press the up and down arrow keys until Reset is displayed, then confirm, and the boiler starts up again. Our Worcester reset guide covers the other control panels.
If you overfill and the reading goes above 1.7 bar, Worcester's advice is to bleed one radiator until the pressure returns to between 1 and 1.7 bar.
Why the pressure dropped
A sealed system should hold its pressure. If 1017 has appeared, water or air has left the circuit for one of these reasons:
- Bleeding radiators. Letting air out always lowers the pressure, and Worcester tells you to top up if it drops after bleeding. Turn the boiler off before you vent radiators, as the 4000 instructions warn against doing it with the heating on.
- A leak on the pipework or radiator valves. Worcester says constant re-pressurising should be investigated as a sign of a leak, starting with pipework and radiator valves.
- A fault inside the boiler. A pressure relief valve letting water out, an expansion vessel that has lost its charge or an internal leak can all pull the pressure down. Our guide to a boiler losing pressure explains how to spot each one.
- A faulty pressure sensor. If the system is full but 1017 stays, the boiler may be misreading it. The 8000 Life manual tells engineers to check the voltage to the pressure sensor and the signal coming back, then replace the sensor.
When to call a Gas Safe engineer
A single top-up after bleeding radiators is routine. Book a Gas Safe registered engineer if any of these apply:
- you need to top up again within a few weeks with no obvious leak
- the pressure reads normal but 1017 will not clear
- water is dripping from the boiler or the pipe outside the wall
- the pressure keeps rising, which the 4000 instructions say needs urgent action from a heating engineer
Leaks on radiators or exposed pipes away from the boiler can usually be fixed by a plumber. Anything inside the casing is a job for a Gas Safe engineer.
Typical repair costs in the UK
| Job | Typical UK cost |
|---|---|
| Topping up the pressure yourself | Free |
| Engineer call-out and diagnosis | Typically £60 to £150 |
| Pressure sensor replacement | Typically £100 to £220 |
| Expansion vessel recharge | Typically £80 to £150 |
| Pressure relief valve replacement | Typically £100 to £200 |
| Internal leak or pipe joint repair | Typically £100 to £300 |