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WATER PUMPS, TANKS, TESTS, WELLS, REPAIRS
WATER CONTAMINANT LEVELS
WATER HAMMER NOISE DIAGNOSE & CURE
WATER ODORS, CAUSE CURE
WATER PUMP REPAIR GUIDE
WATER PRESSURE LOSS DIAGNOSIS & REPAIR
WATER PUMP SHORT CYCLING
WATER SOFTENERS & CONDITIONERS
WATER TANK REPAIR PROCEDURES
WATER TANK: USES, TROUBLESHOOTING
WATER TESTS, CONTAMINANTS, TREATMENT
WATER TREATMENT EQUIPMENT CHOICES
WELLS CISTERNS & SPRINGS
WELL FLOW RATE
WELL WATER PRESSURE DIAGNOSIS
WELL YIELD IMPROVEMENT
WINTERIZE A BUILDING
Short cycling water pumps: well pump turns on and off rapidly or too often: this article defines short cycling or rapid cycling well pumps and the various causes and cures for that problem. We explain why rapid on-off switching of the water pump can be harmful and how it also affects building water pressure. We explain that often sort cycling indicates the need for air in a water pressure tank. In companion articles we explain several ways to add air to a building water pressure tank, and how to detect and correct air and water leaks in a building water supply system where a private well is the water source. We also discuss how to adjust the building water pressure by setting the cut-in and cut-out pressure on the pump pressure control switch.
Green links show where you are. © Copyright 2013 InspectAPedia.com, All Rights Reserved. Author Daniel Friedman.
What is water pump short cycling? - short cycling of the water pressure tank and why can it be harmful?
Several alternative procedures for adding air to a water pressure tank are described below along with advice about what to do when things go wrong, such as finding air and water leaks. The illustration at page top is courtesy of Carson Dunlop, Inc. in Toronto.
Short cycling of a water pump which is defined here at SHORT CYCLING WATER PUMP means that the water pump or "well pump" turns on and off too rapidly or too frequently when water is being run in the building. If this is the problem with your water pump, SHORT CYCLING CAUSES describes the most common causes of this problem. We also provide a complete SHORT CYCLING DIAGNOSIS TABLE that lists all possible causes of well pump rapid cycling on and off. If you are not sure what "water pump short cycling" means or how it is recognized, read SHORT CYCLING WATER PUMP.
Intermittent water pump cycling which is discussed at Intermittent Water Pump Cycling When No Water is Running means that the water pump comes on for no apparent reason.
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 PRESSURE LOSS DIAGNOSIS & REPAIR
The "water storage tank" is doing more than storing water. Its air charge acts like a spring to smooth the delivery of water in the building. If the building water supply pump is "short cycling" - coming on and off rapidly, you may need to add air to the water pressure tank. This step is important to protect your private pump and well from damage due to short-cycling due to loss of air in the pressure tank. Short cycling of the pump motor can burn up the pump relay control.
The minimum that a building owner or occupant needs to know is that short cycling is an on-off cycle of the water pump in a house with a private water pump and water supply well system. The "short cycling" water pump is turning on and off rapidly, perhaps every 10 to 20 seconds or even more frequently. Water pump short cycling can damage the pump or controls. Repair is needed at one or more of: the water pressure tank, water pump pressure control switch, water pump, water filter, or the well or building water supply piping. If you are not interested in tackling this easy repair yourself, call a plumber.
The sketch shown at the top of This article shows the components of a typical residential water well, water pump, water pressure tank, and water pump control system. Below we include other drawings and photographs of wells, water tanks, and their associated valves and controls. At some properties the well pump may be inside rather than in the well as in this drawing, and on your tank the water pressure gauge may be mounted on a special air volume control fitting on the back of the water tank itself rather than as shown in this sketch. Sometimes people think this water tank is to "store" water for use in the building. That's rarely the case. Usually water is "stored" by being present in the well and in the ground around the well.
If a pump-operated water supply system is turning on and off rapidly (every few seconds) it would be smart to turn off the water or turn off electric power to the water pump and call a plumber promptly.
If your water pump comes on at odd times but is not short-cycling, see INTERMITTENT CYCLING WATER PUMPS.
Normally the "pump on" cycle is 30 seconds to 90 seconds or longer, depending on water tank size, and the "pump off" cycle is the same or longer.
What is Water Pump or Water Tank "Short Cycling" - rapid on and off water pump
Short cycling of the water pump means that the water pump keeps turning on and off rapidly whenever you're running water at one or more fixtures in the building. The pump on-off cycle may be perhaps every few seconds, or perhaps every 10-20 seconds. This is a problem, which we diagnose, discuss, and for which we offer repair procedures below. The minimum that a building owner or occupant needs to know is that short cycling can damage the pump or controls, and that action is needed.
These short cycling problems happen with both in-building jet pumps and with in-well submersible pumps. It's trickier to notice a short cycling submersible pump since you won't hear the pump motor, but you will hear the pump relay clicking on and off, or you can see the water pressure gauge cycling up and down rapidly.
If you are not interested in tackling this easy repair yourself, call a plumber. If the system is turning on and off rapidly (every few seconds) it would be smart to turn off the water or pump and call a plumber promptly since if you let this problem continue you're likely to damage a pump control or pump motor (expensive).
You can tell if your water pump system is "short cycling if:
If you don't know how to find your pump pressure gauge, pressure controls, switches and controls, see WATER PUMP & TANK CONTROLS & SWITCHES
How to Detect a Short Cycling Water Pump and Tank
We give more description of how to detect short cycling of the water pump at SIGNS OF AIR LOSS
How to Diagnose the Cause of a Well Pump that Keeps Turning On and Off
Watch out: before "fixing" a short-cycling well pump, you'll want to try for an accurate diagnosis of its cause - the right fix is cheaper than a whole collection of wrong fixes.
See SHORT CYCLING CAUSES for an explanation of the most common causes of well pump short cycling
See SHORT CYCLING DIAGNOSIS TABLE for a table that lists the all of the possible causes of well pump short cycling
If it turns out that you want to just try the easy, quick, above-ground "fix" of adding air to the water tank, we describe how to correct water pump short cycling, in great detail and giving several methods, at WATER TANK AIR, HOW TO ADD for conventional water tanks that do not use an internal bladder.
Bladderless water pressure tanks, because the air charge and water are in the same container, can lose their air charge over time (air is absorbed into the water) and may need air added.
At What Goes Wrong with an Internal-Bladder type Water Tank? we discuss the combination of well pump short cycling and a burst water tank bladder and how this condition is identified and repaired. See these detailed articles on bladder-type "captive air" water tank diagnosis and repair:
Question: should I replace my old water tank?
We just had our pump replaced after 18 years. Total cost with tax was $2400. Project was done on emergency basis on a Friday night and we were really stuck. During his visit the plumber/owner suggested we consider a larger pressure tank than our 20 gallon unit, also recently replaced. The system worked well for many years and I don't see the need to purchase another larger tank. Any thoughts? - Wayne Ouellette
Reply: maybe not.
If your water tank is a newer bladder type, even a smaller 20-gallon tank gives the equivalent of a larger old style (non-bladder) tank in the draw-down cycle - the amount of time that you can run the water before the pump has to come on.
As long as your pump is not WATER PUMP SHORT CYCLING (which may shorten pump life), the gain from a larger tank is probably not much. If your tank is an older type with no internal bladder, the reason to go to a newer tank would be reliability and reduced maintenance.
Some Reasons to Consider a New Water Tank
Watch out: before you go to the trouble and expense of replacing a water pressure tank, make sure that you have correctly diagnosed the problem that you are "curing" - you wouldn't want to replace a water tank only to find that you still have the water pressure or quantity problem because another, perhaps less costly, part was at fault.
Frequently Asked Questions (FAQs) about Short Cycling Water Pumps
Question: Drastic water pump short cycling every 3-4 seconds, sometimes pump won't come on at all, loss of house water pressure
Ok so I have a few problems here. First off my pump is short cycling drastically as in I flush my toilet and within 3-4 seconds I hear the pump kick on. Second, when it kicks on it only stays on for a few seconds before turning off then it only stays off for a couple more seconds before turning back on. And recently about once a day or once every couple days the pump wont come on at all and I have to go down and tap the pressure control switch housing for it to come on. By the time I realize that, we have pretty much lost all pressure in the house due to normal use.
I haven't quite nailed down any tying reasons or times when this happens like my wife doing laundry or something along those lines. When the pump is working we have plenty of pressure, almost too much (water sprays out hard and makes a mess when doing dishes - "lol"). I have looked through this site and have found a bunch of useful information but am overwhelmed and don't have a clue where to start. Any guidance in this matter would be greatly appreciated. - Mark
Reply: Your pump is sort cycling and may be overheating, going off then back on under control of a built-in thermal overload switch
You are describing a classic well pump short cycling problem. Eventually that condition can actually damage the well pump, resulting in less water pressure and flow than previously. You should be able to obtain satisfactory water pressure with the factory settings of your pressure control switch, typically 20/40 or 30/50 cut-in/cut-out.
I suspect that the reason you sometimes lose all water pressure under these conditions is that the rapid on-off cycling of the water pump is contributing to an overheating pump motor. Many electric motors include an internal thermal overload switch. When the motor is too hot, the switch turns off the motor. Later when the motor cools down on its own, the thermal reset switch resets and the pump will run again.
The rapid on-off short cycling well pump may also have led to burning on the contacts of the pressure control switch. That's why sometimes you have to tap the switch to get the pump to run. There could be other pressure control switch problems such as clogging of its pressure sensor due to debris in the water line.
Question: Short cycling well pump, bad pressure settings or bad check valve?
I think my check valve is bad, letting air back to well. Our well pump runs for 3 seconds shuts off for 3 seconds. It does this over and over. I am thinking pressure settings on bladder tank might not be right? - Tim.
Reply: Check for a bad snifter valve and/or a water-logged pressure tank
Before trying to change the pressure settings at the pressure control switch, you should check for a water-logged water pressure tank or another cause of well pump short cycling.
Take a look at the article SHORT CYCLING WATER PUMP - usually the first thing to check is loss of air in the pressure tank; it's true that a bad foot valve or check valve that causes water to bleed back into the well (and thus the tank pressure to drop) can cause the well pump to cycle more often, but that alone wouldn't get us to cycling every 3 seconds. That's more likely a lost air charge or a clog that is not letting the pump get water into the pressure tank;
Also, if your well uses a submersible pump and a water tank that does NOT use an internal bladder, your system may include a snifter valve that is supposed to be letting air into the well piping - as a means of keeping the air charge in the water tank. If the snifter valve has failed (as they can by debris clogging) that could explain a waterlogged pressure tank and a short cycling well pump.
Comment: Draining the water tank, adding air, and adjusting the pressure control switch solved the short cycling water pump problem
Problem: Pump cycling every few minutes for months....Your question and answers solved my bladder type pressure tank cycling problem. I drained the tank and added air to 28 psi (was below 20 psi). I filled/pressurized tank and adjusted limits to 30 (low) and 50 (high). And WOW, now it takes 5 toilet flushings before pump kicks on. I tested the pressure tank psi after pump clicked off and my gauge read 53 psi. So my problem was low air in the pressure tank and limits out of adjustment. Thanks for your instructions that anyone can follow and it saved me lots of money for a plumber.
Bob: Thanks for the nice note; we work hard to make our information useful and unbiased; I'm thrilled it worked for you; we continue to welcome questions or suggestions for our content as together we're smarter than working alone.
Question: My water pressure drops too quickly and reaches cut-out again too quickly
I have a submersible pump and a bladder pressure tank. I have the cut in at 30 and the cut out at 50. My well seem to a lot. If I watch the gauge when pressure hits 30 the pump turns on until it hits 50, but it take only a few seconds for the pump to drop back down to 30, this is with just running a faucet. Should it be cycling that fast? - Robert 7/7/2011
Reply: probably your water pressure tank is waterlogged
Question: possible failed water pressure tank internal bladder
Indeed from reports here tank bladders do fail on occasion; in some water tank designs the bladder can be replaced without replacing the entire tank assembly.
Yes I have read in numerous places that they can fail. This one is 11 years old, have one on order and hope it solves the problem. - Robert Lee
Question: well sort cycles but the tank pressure reads 50 psi
My well has been short cycling recently so I checked the tank pressure. It reads 50 psi. Wondering what is the cause. Could it still be waterlogged tank? - Chris 11/18/2011
indeed in a waterlogged tank the pressure will still go up to the cutoff point - but you'll see a very short drawdown time from when you turn on water in the building to when the pump has to turn back on - that's "short cycling" as we describe above.
Question: well pump loses pressure too quickly when water is taken from the system - drops in 10 seconds
My well pump seems to lose pressure (cut in?) too quickly when water is drawn from the well system. When the water is turned on the pressure drops from 60 PSI to 40 PSI within 10 seconds. Once the system reaches 40 PSI the switch is activated & pressure is restored within a minute of the water being turned off. I believe that I have a tank with a bladder (it an Amtrol tank) & I've tested the pressure of the tank when the well system is active (it reads 38 PSI). I've also tested the pressure after cutting the power to the system & draining the tank (0 PSI). I'm not sure why my tanks loses pressure so quickly & i'm afraid the well motor will burn out soon if this is not corrected. Is this an issue involving the thank bladder? Any advice? - Anon 3/5/2012
Question: when I attach a nozzle or sprinkler to garden hose the well pump no longer runs continuously
My shallow water pump runs just fine with a hose attached with no increased back pressure, but if I attach a nozzle or a sprinkler to the end of the hose, the pump will run for 30 seconds and then shut off. It cycles like that continuously. I have tried increasing and decreasing the air pressure in the bladder to different levels and it does not seem to correct the problem. How do I know the correct air pressure? It is not written anywhere on the pump or the valve. Any other suggestions? - Dr. Louis Gotthelf 9/26/2012
Question: water pump turns on and off a lot, and water temperature in the shower then fluctuates
I have a water pump that seems to turn off and on a lot when we run water, especially in the shower. When the pump turns on, our water temperatures fluctuate. We thought it was the water heater so we replaced that. Water temperatures appear better but the fluctuation is still there. We do have a leaking water hose connection outside of our home but just drips. Could that explain the water pump running a lot? Since replacing our water heater we also lost some of our water pressure on the hot water, cold water is fine. Can you explain what could be causing the temperatures to fluctuate when the water pump turns on? Our water source is spring fed if that helps at all. Thanks! - Jennifer Beckler 10/3/2012
Questions & answers or comments about diagnosing and repairing a short-cycling well pump: how to fix a well pump that keeps turning on and off too frequently
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