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Schematic of a submersible pump deep well system (C) Carson Dunlop Associates How Does a Submersible Well Pump System Work?

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This article describes the sequence of operating steps in a submersible well pump water system.

The process of diagnosis and the costs of the repair are explained. Consumer advice on saving money on water supply repair costs includes a review of the parts and labor costs of a typical well pump and pressure tank replacement case.

Carson Dunlop's sketch at page top shows the components of a submersible well pump water supply system.



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How a Submersible Well Pump Water System Works - Sequence of Operating Steps

Photograph of a drilled well casing

What happens when you turn on the water at a faucet in a building whose water is supplied by a submersible well pump?

The following steps describe normal operating of a building well pump and water supply system. Other cases in which the well pump controls are not working properly, there is a problem with the controls, pressure tank, pump, or well itself are discussed
at WATER PRESSURE REPAIR GUIDE & COSTS
and
at WELL WATER PRESSURE DIAGNOSIS. Our sketch (left) shows a cutaway view of a submersible well pump.

[Click to enlarge any image]

  1. Turn on building water at a plumbing fixture: open a sink valve, tub valve, or flush a toilet.
  2. Water runs out of the supply faucet, into the fixture, down the drain
  3. Water pressure and flow are being supplied to the building from a water pressure tank. If we didn't use a pressure tank, because water is not very compressible, the second water was turned on, water pressure in the system would drop below the pump cut-on pressure, the pump would turn on, and probably bring water pressure up to the cut-off pressure quickly, causing short cycling and burning up pump controls or a pump motor.

    See WATER TANKS HOW THEY WORK.

    Note: The illustration at above left is adapted from an original drawing by Trisha A.D. Nelson, A.C.E., Inc., is a consulting engineering firm in Atlanta, GA. Website: www.aceforensics.com
  4. Pressure in the water pressure tank and in the building piping system drops down to the well pump cut-in pressure. Typically this is 20 or 30 psi on a residential water system. On a submersible well pump system the cut-in pressure may be as much as 40 psi.
  5. The well pump pressure control switch senses the pressure drop, closes an internal electrical relay switch to turn on the submersible well pump.
    See WATER PUMP PRESSURE CONTROL SWITCH.

OR

Submersible well pump (C) Daniel Friedman

  1. A separate pump relay switch turns on the submersible well pump as follows: the well pump pressure control switch senses the pressure drop, closes its internal electrical relay switch to in turn send power to a heavier-duty pump relay switch (usually mounted on a wall near the pressure tank and other water controls). The pump relay switch actually turns on the well pump.

    In the submersible well pump photo above you can see extra pump relay switch boxes at the left of the red arrow. The arrow itself points to a submersible well pump that has been removed from the well and left in the utility space that houses a water pressure tank and control that are partly visible in the right side of the photo.

    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.
    See WATER PUMP RELAY SWITCH.
  2. The well pump motor runs, drawing water back into the building from the well by "sucking" water up from a shallow depth (a one-line jet pump can't draw water from much below 25 feet)
  3. Water is forced into the building water pressure tank and simultaneously into the building piping and on to the plumbing fixtures.
  4. If the pump sends water into the building faster than water is flowing out of the open faucet or plumbing fixture, the pump will "get ahead" of the water flow, successfully pressurizing the water tank, causing the pressure switch to turn off the pump (see step 10 below).

    OR
  5. If the pump cannot send water into the building faster than water is flowing out of the open faucet or plumbing fixture, the well pump will run continuously and water will flow out of the open faucet or plumbing fixture at a rate limited basically by the pump's water delivery flow rate in gallons per minute. You'll also find this condition if a building water supply pipe bursts.

    We say "basically" because the well piping and building piping and faucets themselves offer some back-pressure against the pump's flow rate. In this case, the well pump will continue to run until the building faucets or plumbing fixtures are turned off. At that point ...
  6. The well pump pressure control switch senses that water pressure has increased to the cut-out point, opening its switch and turning off electrical power to the well pump. The well pump has re-pressurized the building water tank and piping up to the cut-out or cut-off water pressure.

    Cut-out pressures are typically set to 40 psi or 50 psi. If you set the cut-out pressure too high the pump may never reach it and will run continuously, or you may find frequent plumbing leaks, or even an unsafe condition, risking bursting a pipe or water pressure tank. Many submersible well pumps are capable of pumping to high enough pressure to damage the plumbing system or burst a water tank. That's why water pressure tanks need a pressure relief valve installed.
  7. The foot valve closes (at the bottom of the well piping) and/or a check valve located in the building on or close to the well pump closes, preventing water and pressure from flowing backwards down into the well, losing building water pressure and possibly losing pump prime

    . However because the submersible pump is inside the well at the bottom of the well piping, loss of prime is not a problem directly - that is, the submersible pump, because it is under water, will have no trouble re-starting. But still a bad check valve or foot valve means you may lose building pressure between well pump cycles.
    See WELL PIPING FOOT VALVES
    and
    see WELL PIPING CHECK VALVES.

Where is the Well Pump?

Photograph of a drilled well casing

Take a look at our well casing photograph at above left. See that small gray conduit rising at the left side of the well casing? The conduit carries electrical wires into the well. That's one way to recognize that a submersible pump is installed.

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.

How to Diagnose Poor Submersible Pump Water Pressure

For our complete water pressure and pump, well, and piping problems diagnostic article list,
see WATER PRESSURE REPAIR GUIDE & COSTS
and
see WATER PRESSURE LOSS DIAGNOSIS & REPAIR.

Separately we also provide
a WATER PRESSURE PROBLEM DIAGNOSIS TABLE. 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
    at WELLS CISTERNS & SPRINGS.

    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
    (WATER PUMP PRIMING PROCEDURE)
    and a bad or leaky well piping foot valve
    (WELL PIPING FOOT VALVES).
  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
      at ADJUST PUMP PRESSURE CONTROL.
    • 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
      at SIGNS OF AIR LOSS.
    • 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 at JUST SOME FIXTURESust 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.

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Continue reading at WATER PUMP, SUBMERSIBLE or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.

Or see SUBMERSIBLE PUMP TORQUE PROBLEMS & SOLUTIONS

Or see SUBMERSIBLE PUMP DIAGNOSTIC FAQs for diagnostic questions & answers

Or see DIAGNOSTIC TABLE for WATER PUMPS

Or see WATER PRESSURE PROBLEM DIAGNOSIS TABLE

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PUMP, SUBMERSIBLE OPERATION at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

INDEX to RELATED ARTICLES: ARTICLE INDEX to WATER SUPPLY, PUMPS TANKS WELLS

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