Lately, under certain circumstances our house pump that uses a small pressure tank will not shut off even when the pressure is high enough.

So far it only happens when I use the garden house to play with our dog. I don't use a sprayer, just the hose because the dog has more fun. I fold the hose over and plug the end with my thumb and then release quickly and our dog loves the sudden arc of water that results. After doing this 2 or 3 times, I feel the water pressure is still decent but weaker than normal. I then go check the pump and it is running continuously. I leave it run a few minutes... still running. The first time this happened I unplugged the pump cord and let it sit for ½ hour. When I plugged it in, the pump resumed normal operation.... shutting off after system is sufficiently pressurized.

The same thing happened just now. I also tried closing the valve that is on the output side of the pump.... doesn't help... pump still running. I unplugged for 10 minutes and when plugged back in the pump only made a low volume humming sound. When I briefly opened a nearby valve the pump started but again would not shut off.

I unplugged the pump, opened a nearby valve and kept it open until the pressure in our whole system was released. We have two houses with many bathrooms and kitchens connected to the single house pump so there is a lot of piping. Consequently it takes a while for the pressure to subside. I then closed the valve and restarted the pump.....problem gone!

What's going on?

Is the pressure buildup in the garden hose followed by sudden release damaging the pressure switch that is supposed to turn off the pump?

Very hard to say exactly what is happening, but would say it could well be something connected to the pressure switch.

Are you confident to remove the cover on the switch and replay the sequence that initiates the problem while watching the switching operation - maybe it flutters and when jams "on".

Keep fingers and water away from the exposed switch.

1 hour ago, gamb00ler said:

our house pump that uses a small pressure tank

So It is an EP series pump?

It is controlled by a flow switch. 850 ++Baht on Shoppee The little square box above the label.

When in doubt tap it with the handle of a screwdriver when the pump won't stop. I think the switch is more hi-tech than that but...

Symptoms when this Flow Switch is faulty.

When the flow switch or flow control switch is faulty or damaged, your water pump will exhibit the following symptoms:

• Pump doesn't turn on when tap is opened: The pump doesn't operate when the tap is turned on.

• Pump doesn't shut off when tap is closed: The pump continues to run even after the water tap is turned off.

• Frequent pump on/off: The pump is switching on and off too often, without a consistent rhythm.

• There is an unusual editing sound: a "clicking" sound or other abnormal editing noise.

• Unstable water pressure: Water pressure fluctuates between high and low.

• The pump runs continuously: The pump operates even when no water is being used.

• No water is coming out of the tap: You turn on the tap but no water comes out because the pump isn't working.

• Slow start pump: The pump starts slowly after the tap is opened, with a long delay.

• Flow switch not responding: Water is flowing but it is not being detected.

• Pump stuck running: The pump is on and does not turn off; it runs continuously.

• Water pressure too low: Water flows weakly, no pressure.

• Water pressure is too high: The water sprays out too forcefully and is uncontrollable.

• Leakage: Water is leaking from the flow switch.

One can never be sure but...

If it is a WP series.

See above post about pressure switch.

Edited May 26May 26 by VocalNeal
Fecking about trying to insert an image

Quite common. It may be a clogged pressure sensor tube or pressure switch nipple.

Check the pump manual for how to clean the pressure sensing tube/port. These small passages can get partly blocked by lime, rust, sand, or other debris, which can stop the pressure switch from sensing the real system pressure.

I always keep a spare pump ready. This happened once while I was away, so they simply switched pumps. When I came back, I searched online and cleaned the clogged sensor tube with a needle and some CRC.

Vinegar 7% can also be used if there is lime buildup, or if you do not want CRC smell in the water. Even a small amount of CRC can leave smell and taste for a few days, especially when brushing teeth with the water.

After cleaning the tube, the original pump was as good as new again.

Edited May 26May 26 by Hummin

12 minutes ago, VocalNeal said:

So It is an EP series pump?

No it's a Grundfos setup. It's around 3 years old. Quiet and great pressure.

Edited May 26May 26 by gamb00ler

I would be looking at pressure switch.

Try bumping or hitting the pressure switch, a little bump, see if that fixes it. If it does, may need a new pressure switch.

I notice on my Mitsabishi that sometimes after a lot of use the contacts must get stuck together, a small tap or bump fixes that.

Shouldn't happen, but metals aren't metals anymore.

Putting in a new thermal overload for my contactor and the previous Mitsubishi overload I could torque the screws to recommended torque, but the new overload just nearly stripped the screw heads.

2 hours ago, gamb00ler said:

No it's a Grundfos setup. It's around 3 years old. Quiet and great pressure.

Hit the black box with a screwdriver handle next time it happens.

That may indicate where the problem is.

If you are handy, as before stated take the cover off and have a look.

Would have saved time at the begining if you had stated Name, rank and serial number.😉

Edited May 26May 26 by VocalNeal

You ned to disconnect the electric wires and take the switch out to see the tiny hole where the pressure is measured. It might not be enough to poke a needle in the hole, it can be something behind where the rubber sheet is that push against the spring. In another place I had the whole thing full of lime when I took it apart. I have the same pump, done it. My problem was a blocked check valve, I found it out too late... 15 min work and very simple.

4 hours ago, VocalNeal said:

Hit the black box with a screwdriver handle next time it happens.

I might use the rubber covered handle on one of my hammers. So far I only used my knuckles to rap on the black box. Didn't really get much oomph out of that attempt.

As suggester earlier take the top off and observe the action of the switch. Be very careful not to touch anything inside . Many guys get killed fixing , say. pool pumps.

If you need to remove the switch shut the power off.