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This article describes How to diagnose & repair water pump intermittent cycling - the water pump comes on when no water is being run in the building. Intermittent water pump cycling which is discussed in this article means that the water pump comes on for no apparent reason. Short cycling of a water pump means that the water pump turns on and off too rapidly or too frequently when water is being run in the building.

See What Causes "Water Pump Short Cycling" and Water Tank Repairs: Diagnose "Water Pump Short Cycling". Loss of water pressure means that the pressure with which water enters a plumbing fixture has become too slow, or is sometimes too slow or weak in water flow rate, or water flow may stop entirely. See Water Pump Problems? How to Diagnose & Repair Poor or No Water Pressure. The illustration at page top is courtesy of Carson Dunlop, Inc. in Toronto.

What is Intermittent Water Pump Cycling, What Causes It, and How is it Corrected?

Intermittent water pump cycling which we explain here means that the water pump comes on for no apparent reason - that is, you are unaware of any water running in the building. (When water is running in a building served by a private well and water tank and pump system it is normal for the water pump to cycle on and off to deliver water to the building.)

Here are the more likely causes of the water pump coming on at odd times when you're not (aware of) running any water. You may want to investigate these possible causes roughly in the order they are listed below.

1. Running Toilets: A toilet somewhere in the building is running - this can be VERY hard to spot - unless you are meticulous. I've tried wiping the toilet bowl interior to make it dry and then feeling it later for wetness above the water line, or watching the water in the toilet bowl for ripples, or placing a little septic dye or food coloring in the toilet tank to see if it appears in the bowl below, or, simplest, simply turning off all toilets at their supply valve to see if the pump cycling goes away. A leaky flush valve or a leaky fill valve in a toilet causes this problem.
2. Leaky Plumbing Fixtures: A plumbing fixture such as a sink, tub, shower, or clothes washer is leaking slowly - dripping into the fixture (where you can see it) or worse, dripping into a hidden building cavity such as a wall or ceiling cavity (where water stains eventually show up below) or into a floor or crawl space (where you may not see the leak).
3. Leaking Water Tanks: An air leak at the water pressure tank, above the water line in the tank, (or a water leak from the water pressure tank) can cause the tank to slowly lose air and the water pump to cycle on. This is possible with both traditional steel water tanks and with modern captive-air bladder type tanks (water is in a separate bladder inside the tank). Older water tanks which have an air volume control (which rarely work) are designed to automagically add air to the water tank as needed, so if the AVC is working and if there is a little air leak on the tank somewhere (often you can spot a rusty pinhole leak), this condition could continue for a while before being diagnosed.
4. Leaky check valve or foot valve: A check valve at the pump or a foot valve in the well at the bottom of the water pipe could be failing and leaking, sending water backwards from the pressure tank, through the water pump, and back into the well. This can eventually lead to loss of prime and loss of all water supply as is discussed at our website.
5. Leaks in well piping: A water leak in the well piping between the building and the well or even inside the well could also cause a back-flow of water from building to well and lead to pump cycling on and off.
6. Defective Pressure Control Switch: A defective pump pressure control might, in theory cause this intermittent cycling but in more than 30 years of practice I've not found this to occur.

To Fix Water Pump Intermittent Cycling

To correct the problem of water pumps coming on when there is no apparent reason, we need to find which of the causes listed above is occurring. Remember that on occasion more than one fault could be present. Each of the possible causes listed above is also discussed as a diagnosis and repair topic at this website. Use the links at page left or the "Search Box" on any of our web pages to look for further advice.

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PLUMBING TOPICS
APPLIANCE EFFICIENCY RATINGS
OIL TANKS
SEPTIC SYSTEMS
WATER PRESSURE REGULATOR ADJUST
WATER PRESSURE REPAIR GUIDE & COSTS
WATER PRESSURE LOSS DIAGNOSIS GUIDE
WATER PRESSURE & FLOW MEASUREMENT
  WATER PUMP PRESSURE CONTROL ADJUSTMENT
  WATER PUMP PRESSURE CONTROL REPAIR
  WATER PRESSURE REGULATOR ADJUST
WATER PUMPS & WELL TANKS
WATER PUMP CONTROLS & SWITCHES
PUMP TYPES & LIFE EXPECTANCY
WATER PUMP & TANK SAFETY
WATER SHUTOFF VALVE LOCATION, USE
WATER SOURCE ALTERNATIVES
WATER SUPPLY & DRAIN PIPING
WATER TANK TYPES: WATER, OIL, EXPANSION, ALL
WATER TANK LIFE EXPECTANCY
WATER TANK REPAIRS
  CONTROLS & SWITCHES on WATER TANKS
  INTERMITTENT CYCLING WATER PUMPS
  WATER PUMP SHORT CYCLING
  SHORT CYCLING DETECTION
  SHORT CYCLING CAUSES
WATER TANK AIR, HOW TO ADD
  WATER TANK AIR LOSS SIGNS
  WATER TANK AIR VOLUME CONTROLS
  WATER TANK AIR ADD AT AIR VALVE
  WATER TANK AIR ADD BY DRAINING
  WATER TANK AIR HOW MUCH TO ADD
  WATER TANK AIR HOW OFTEN TO ADD
WATER TANK REPLACEMENT
WATER TANK BLADDER PRESSURE ADJUSTMENT
WATER TANK PRESSURE CALCULATIONS
WATER TANK PRESSURE GAUGE
WATER TANK SIZE & VOLUME
WATER TANKS HOW THEY WORK
WATER TESTING
WELLS CISTERNS & SPRINGS

Other articles that might be helpful in diagnosing this intermittent water pump cycling include (read them in this order):

• Water Storage & Pressure Tanks - How They Work
• How a Bad Water Tank Causes Loss of Water Pressure or No Water
• What Causes "Water Pump Short Cycling" - a water pump turning on and off too rapidly
• Water Tank Repairs: Diagnose "Water Pump Short Cycling" & Restore Air in a Building Water Tank
• Signs of Air Loss from a Home Water Tank
• How to Diagnose & Repair a Bad Water Pressure Regulator
• Water Pump Problems? How to Diagnose & Repair Poor or No Water Pressure

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