Water pump pressure switch (C) Daniel Friedman Dropping water pressure
How to Diagnose & Repair Slowly-Dropping Water Pressure

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Troubleshooting deteriorating water pressure in buildings: this article describes how to diagnose slow water pressure loss and erratic well pump behavior.

When water pressure seems to keep dropping after the well pump has stopped, what's wrong? How do we fix it? How to diagnose and fix erratic well pump or pressure control switch behavior.

Here we discuss tracing a water pressure problem to pressure gauge, pressure switch, pump relay, check valve, foot valve, or building water leaks. We explain how to decide if water pump pressure control switch or water pump replacement is needed.

Step by step diagnostic procedure for falling water pressure trouble.

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Diagnose slow pressure or loss of water pressure in a building after the well pump has cycled off

Causes of bad water pressureCommon causes and repairs for erratic well pump or pressure switch behavior

This article discusses water pressure that falls slowly when it should be more steady - diagnosis & cure.

Short cycling of a well pump (see WATER PUMP SHORT CYCLING) is also a type of "intermittent lost water pressure" except that water pressure fluctuates between stronger & weaker rapidly, perhaps every few seconds. Short cycling has several different causes, including a partly-clogged sensor on the pressure switch (blocked by debris, water pressure is slow to enter the pump control, and slow to leave it).

A similar problem can happen at a pressure gauge, making the gauge slow to register an increase and then to bleed down, showing a pressure drop more slowly than the actual water pressure drop.

Meaning of a Slow Responding Well Pump Pressure Switch

A slow response of a well water pump pressure switch (WATER PUMP PRESSURE CONTROL SWITCH)

and/or pump relay control (WATER PUMP RELAY SWITCH) to the actual water pressure suggest a blocked pressure switch sensing port - due to debris in the water or hard water. This problem can also cause a delayed-response of the pressure control or gauge to the actual system water pressure.

Note that water pump relay switches are often installed when the well pump is actually down in the well (a submersible pump) while in-building water pumps (1 line or 2-line jet pumps) will not usually require the heavy-duty pump relay control. Instead the in-building pumps are controlled directly by the pressure switch.

Meaning of Building Water Pressure Drop to Zero

A building water pressure drop to zero when the well pump is still able to switch on and restore water pressure (if the gauge is accurate - see WATER PRESSURE GAUGE ACCURACY) suggests a bad foot valve or bad check valve that is letting water pressure drain back into the well.

If building water pressure is lost entirely and does not immediately recover when the pump turns on, see WATER PRESSURE LOSS DIAGNOSIS & REPAIR.

When building water pressure appears to drop after the pump is turned off, some causes include

Photo of a water pressure gauge showing pressure below pump cut-in

Sorting Out the Job of the Pressure Switch vs. the Pump Relay Switch

We were unsure about the "clunk" reported by a reader as an intermittent sound at the pump relay, but a possible explanation would be confusion between what the little WATER PRESSURE CONTROL SWITCH (also referred to as pump control switch or "pumptrol" or "pressure switch") is doing versus what the heavy duty PUMP RELAY SWITCH is doing.

Normally, the water pressure at the pressure sensing switch is what turns the pump on and off, either by directly switching the pump on and off in response to sensing the cut-in or cut-out pressure at the pump or water tank, OR indirectly by turning on and off a heavy-duty pump relay switch that is used to turn higher horsepower and thus higher amperage-drawing (submersible) well pumps on and off.

Photograph of  a modern steel well casing and cap extending properly above grade level and properly capped. You can see from
the gray plastic conduit that electrical wires enter the well, informing you that this well is served by an in-well submersible well pump.Running a high-amp well pump off of a little pressure control switch will often burn up the switch contacts, or the amperage draw may exceed the rating of the pressure switch itself - that's why the relay switch is used.

So the "duty cycle of the pump" cited by our reader doesn't seem to explain this problem, though some other electrical problem in the pump wiring or controls could be causing the pump to cycle on and off while the pressure switch continues to call for pumping - such as a faulty thermal overload switch.

When a water pump is inside the well, it can be tricky to know when the pump is actually on or off, though usually we hear the pump relay clicking, and some relays have a light that indicates that the relay is telling the pump to run.

The pressure switch calls for pumping by switching a relay in the pump relay, that actually turns the pump on and off. So a secondary potential problem would be in the relay itself, but we would look at the pump pressure control switch first.

List of Diagnostic Steps for Slowly-Falling Building Water Pressure

Reader Question about Dropping Water Pressure

I have a residential well that is about 11 years old. I believe the pump itself is a submersible type located at the end of the pipe at the bottom of the casing in the back yard.

In the house, there is a bladder type pressure tank, a control box on the wall, a pressure switch and guage on the water pipe. After that is the water filter and water softener. Then it branches out to the house.

My Well pump is short cycling. Here's what I see:

Looking at the pipes in the basement where the well attaches to the house water system, I watch the water pressure guage. Its at 60 psi.

I open a facet and run some water until the well pump turns on. The pressure guage is about 40 psi when the pump turns on. I stop running water.

The pressure rises to about 55 psi and the well pump turns off. I watch the pressure guage and it slowly drops a few psi while maybe 10 seconds have passed.

The slow water pressure drop problem and its diagnosis are discussed in this article

The pump turns back on and pumps up to about 58 psi and turns off

I watch the pressure guage and it slowly drops a few psi while about 10 more seconds pass. The pump turns back on and pumps up to 60 psi and now I hear a solid "clunk" noise in the well control (relay) box on the wall and the pump turns off.

This time, there is no drop in pressure and the pump does not turn back on unless I use more water.

I found this information about the "foot valve" and "well pump pressure" that may help explain the cause but what is the "clunk" noise and why doesn't the clunk happen every time the pump cycles?

Does the clunk only happen when the foot valve is engaged?

Or is the well pump unable to produce 60 psi every time and has its own shut-off at the pump itself?

Well piping foot valve leaks:

In some cases a defective foot valve in the well can cause water to drain back out of the building system into the well, dropping pressure in the water tank and causing the pump to run mysteriously.

The "foot valve" is an anti-siphon device intended to hold water in the pipe that rises up inside the well after the pump has shut off. If the foot valve is damaged you'll need a plumber to pull the well line and replace the valve.

The foot valve itself is an inexpensive part but pulling the well line can be costly. On the author's well the foot valve lasts typically about 20 years.

Well pump pressure:

Exceeding well pump pressure capability: If you set the cut out (stop pumping) pressure higher than the water pump is capable of reaching, the pump will just keep running indefinitely until it burns up or blows a fuse or trips a circuit breaker or overheats.

General Tips for Diagnosing Water Pressure Problems

Causes of bad water pressure Carson Dunlop AssociatesThis sketch, courtesy of Carson Dunlop, shows five factors that affect the water pressure and flow in a building. What the sketch has not included are water pressure, quantity, or flow problems that originate at the well, well pump, or water pressure tank. Here is our comprehensive guide to diagnosing bad water pressure.

If you have no water pressure at all, see No Water Pressure and see the other water pressure diagnostic articles listed just below.

If your water pressure is intermittent, starts and stops, or varies in pressure,
see WATER PRESSURE INTERMITTENT LOSS and see the other water pressure diagnostic articles listed just below.

If there is some water pressure but the pressure and/or flow are poor? See the diagnostic articles listed just below.

Water supply piping problem? See Bad water pressure Clogged Pipes


Keep in mind that if water is running elsewhere in the building (another shower, sink, dishwasher, clothes washer, garden hose, etc) then the water pressure you will observe at your location will usually be reduced.

If you have good cold water pressure but not enough hot water pressure or hot water quantity,

If you have good water pressure at some fixtures but not at others, you probably have a clog in building piping (such as due to mineral deposits, rust, or even excessive solder in new work), or mineral and debris clogged strainers at faucets and shower heads (check these first). Also


How to Diagnose Poor Well Water or Pump Water Pressure

For our complete water pressure and pump, well, and piping problems diagnostic article list,



The following articles pertain if you have a private well, pump, and tank system for your building or if your incoming community water supply pressure and flow are just too low to start with:

  1. Water Tank Problems? See WATER PRESSURE TANK REPAIRS. Examples of water tank problems include poor water pressure or the well pump rapidly turning on and off (short cycling).
  2. Water pump problems? Examples of water pump problems include poor water pressure or no water pressure at all. See
  3. Water piping or well piping problems? If your water pump keeps losing prime, a shallow well jet pump well line could have a bad foot valve
    (in the well WELL PIPING FOOT VALVES) or there may be a bad check valve on well piping at or near the water tank or near the above-ground water pump

    (CHECK VALVES, WATER SUPPLY) and so be losing prime. A leak in the well line piping itself can also lead to loss of prime.
  4. Well Problems? Do you run out of water or after running water for some interval water pressure and flow are poor? Well problem diagnosis starts
    Before assuming that there is no water in the well, check to see if the water pump is working properly, including loss of pump prime

    a bad or leaky well piping foot valve
  5. Bad water pump or water tank pressure regulator control? 
    See WATER PRESSURE REDUCER / REGULATOR (not usually installed on private well and pump systems, often present on municipal water supply systems that use an in-building local water pump and pressure tank to boost pressure). Water pump pressure regulator switch diagnosis and repair steps include these:
    • How to Adjust Water Pump Pressure: The detailed, step by step procedure for inspecting and adjusting the water pressure control switch is discussed in detail
    • Diagnosing Water Pump Short Cycling on and off: If your water pump is clicking on and off too often or quite rapidly
      see SHORT CYCLING.
    • Diagnosing Water Pressure Drops without explanation when the pump stops,
      see WATER PRESSURE FALLS SLOWLY, ERRATIC PUMP: bad pressure control switch, building water running or leak, bad pressure gauge, bad check valve, bad foot valve.
    • Diagnosing & Repairing Lost Air in the Water Tank: The problem of lost air in the water pressure tank along with how to correct that condition are discussed beginning
    • Diagnosing & Repairing a Water Pressure Control or Water Pump Control Switch: We discuss diagnosing and repairing a water pressure control switch that sticks "on" or "off" or simply won't operate,
      at water pump Pressure Switch Repairs.
  6. Bad Hot Water Pressure? 
    See HOT WATER IMPROVEMENT especially if the building cold water pressure is acceptable but hot water pressure and flow are poor. Accumulated debris in a water heater, and debris from a corroded or disintegrating hot water tank dip tube or hot water tank sacrificial anode can also block the hot water outlet opening, resulting in low hot water pressure in a building.
  7. Bad cold or hot water pressure and flow just at certain plumbing fixtures? See our discussion of
    Poor water pressure just at certain plumbing fixtures just above.
  8. Problems with water treatment equipment can cause loss of water pressure or no water flow: a clogged water filter, or a malfunction in water disinfection or other water treatment equipment can cause a reduction in water pressure or even a complete stop in water flow in a building.
    See WATER FILTERS, HOME USE for details about clogged filters, and

    see WATER TREATMENT EQUIPMENT CHOICES for our complete list of types of water treatment equipment.


Continue reading at WATER PRESSURE FALLS BRIEFLY THEN STOPS - after the pump turns off pressure falls a few psi, or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.

Or see BOYLE's LAW where we explain P1V1 = P2V2 at constant temperature

Or see WATER PRESSURE INTERMITTENT LOSS - occasional loss of water pressure

Or see WATER PRESSURE FALLS SLOWLY FAQs - questions & answers posted originally in this article

Or see WATER PRESSURE COMES & GOES - water pressure is lost, then returns

Or see these common sources of slow dropping in water pressure and loss of well prime:



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WATER PRESSURE FALLS SLOWLY, ERRATIC PUMP at - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.


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