A pump that never stops means the pressure isn't reaching the stop value or the stop command isn't carried out. Six common causes, from a high F1 and leaks to the bypass valve and the F8 delay, and the order to check.
A pump running non-stop means it starts and then never stops, even when every tap in the building is closed. This problem is different from the pump constantly starting and stopping, and its causes are different too. A pump that runs for hours without a break uses a lot of electricity, and if water also stops reaching it, it burns out within minutes.
When the pump should stop
The controller stops the pump when the line pressure reaches F1. In HYDROSET's factory setting F1 is three bar. So a pump that runs non-stop means one of these two things:
- The pressure never reaches F1.
- The pressure gets there, but the stop command is not carried out, or is carried out late.
Look at the display first
Close every tap and follow the pressure figure on the controller display for a few minutes. If the pump switch is mechanical, do the same with the gauge on the pressure vessel.
| What you see | It means |
|---|---|
| The pressure rises but stops a little below F1 | The pump can't reach F1; cause 1 |
| The pressure stays low or goes up and down | Water is going somewhere; causes 2 and 3 |
| The pressure has reached F1 but the pump is still running | Stop delay; cause 5 |
Cause 1: F1 above what the pump can do
If F1 is set higher than the pressure the pump can build, the pump never stops. The manual has a simple rule: the head on the pump's nameplate must be more than "building height + 20 metres".
Work out the pressure you need with a simple formula too: F1 equals the building height in metres divided by 10, plus 2. For a 10-metre building, that is three floors, an F1 of three bar is enough. If someone has raised F1 for "more pressure", set it back to this figure.
A worn pump may also no longer reach the pressure it did when new. If F1 has been the same for years and the pump has only now started running non-stop, consider pump wear too.
Cause 2: an open tap or a leak
A garden tap not fully closed, a toilet cistern that keeps filling, or a leak under the floor takes water out of the line and keeps the pressure down. Close every tap and look at the meter; if the meter is turning, the leak is after the meter. The full method is in How to measure water pressure in a building.
Cause 3: the bypass valve
If you have a bypass line, check its valve. A bypass valve that looks closed but leaks because it is faulty keeps the pressure from reaching the set value.
Cause 4: the pressure sensor is not reading correctly
The sensor must be fitted after the check valve; if it sits before it, it does not read the real line pressure. There is a green light on the back of the sensor, and it being lit means the sensor is sound. If it is off, the sensor or its cable is faulty and the unit shows fault E6.
Cause 5: stop delay (F8)
Parameter F8 sets how many more seconds the pump runs after the pressure reaches F1. Its range is 0 to 600 seconds and its factory value is 0. If someone has raised it, the pump stays on for up to ten minutes after the pressure is reached and appears to run non-stop.
Cause 6: a mechanical pressure switch
In a mechanical automatic switch, a spring and a diaphragm make and break the contact. If the contacts stick together, or the spring screw has been tightened beyond what the pump can deliver, the pump does not cut out. These switches are not set with a number but with a screw; see the difference between a pump controller and an automatic switch.
When the water is cut as well
A pump that runs non-stop with no water reaching it runs dry and burns out. The HYDROSET controller detects this from a drop in the pump current (E3) or from pressure that fails to build (E4) and stops the pump. A mechanical pressure switch has no such protection. Details in Dry running: causes and prevention.
The order to check
| Order | What to check | Sign |
|---|---|---|
| 1 | Open taps and leaks | The meter turns with the taps closed |
| 2 | Bypass valve | The pressure stays a little below the set value |
| 3 | F1 value | Above height ÷ 10 + 2 |
| 4 | F8 value | The pump stays on after the pressure is reached |
| 5 | Sensor green light | It is off |
| 6 | Pump head | Below building height + 20 metres |
You can also see this behaviour in the pump controller simulator: the pump stops only when the pump room pressure reaches the stop value. The permitted range of every parameter is in the user manual.
