Constant running vs. frequent cycling
These get described the same way by homeowners and mean different things, so it is worth separating them before anything else:
| What you're hearing | Likely means |
|---|---|
| Cycles more often than usual - runs for a normal-length burst, shuts off, runs again a few minutes later, repeating through the day | Usually normal wet-season behavior. More water is arriving at the basin, so the pump works more often. Not itself a problem. |
| Runs continuously - motor stays on for extended periods without shutting off | Either genuinely more water arriving than the pump can keep up with, or the pump is running without actually moving water (a stuck switch, an air-locked or blocked discharge line). Worth investigating rather than waiting out. |
| Short-cycles - turns on and off every few seconds, repeatedly | A mechanical problem: a float switch set wrong, a failed check valve letting water flow back into the basin, or an undersized basin for the water volume arriving. This is the pattern most likely to burn out a motor. |
When it is actually normal
A sump pump's whole job is to turn on when water reaches a set level and shut off once it has removed it, and in a Seattle-area winter that can mean dozens of cycles a day without anything being wrong. Signs this is ordinary wet-season operation rather than a problem:
- Cycling tracks recent rain - more frequent during and right after storms, less frequent during dry stretches.
- Each cycle runs for a normal duration and clearly shuts off between cycles, rather than staying on continuously.
- The water level in the basin visibly drops each time the pump runs.
- No unusual noise, vibration, or smell of a hot motor.
When it is a warning sign
Several patterns point toward an actual problem rather than a hard-working pump:
- The motor never shuts off, or shuts off only for seconds before restarting.
- Short-cycling - on and off every few seconds in a repeating pattern.
- Running but the water level is not dropping - the pump is on but not actually discharging water, which points at a clogged or frozen discharge line, a stuck check valve, or a failed impeller.
- A grinding, rattling, or humming-without-moving-water sound - possible impeller damage or a jam.
- The pump is noticeably hot to the touch or smells of hot electronics after running.
- Water is still rising in the basin despite the pump running, which means the water arriving has genuinely outpaced what the pump and its discharge line can move.
Any of these justifies looking closer rather than assuming the pump will sort itself out once the rain lets up.
Why Seattle-area pumps work harder in winter
Two regional facts explain why a sump pump here sees real winter demand even when nothing is wrong with it. NOAA's 1991–2020 normals for Seattle-Tacoma International Airport put 75 percent of the year's 39.34 inches of rain in October through March, spread over about 93 days a year with a tenth of an inch or more, so the water arrives as a long, steady supply rather than a few big storms. And much of the area sits on glacial till, the dense layer known locally as hardpan: Seattle's landslide study says water perches on top of it and normally dries up in spring or summer and returns in winter, and USGS found shallow wells in the till of southwest King County holding water in winter and nearly dry by late summer. Water that reaches a foundation on that ground lingers rather than soaking away. Put those together and a working pump earning its keep through a Seattle-area winter is unremarkable, and one that sits idle from June to October is normal too. The question this page is actually answering is when that normal winter workload has tipped into something the pump, the switch, or the system feeding it cannot keep up with.
What happens if you ignore it
A pump that is failing rather than just busy does not usually announce it cleanly - it tends to get slowly worse across a wet season and then fail outright during the storm that needed it most. Left unaddressed:
- Motor burnout. Continuous running and short-cycling are both harder on a motor than its designed duty cycle, and a motor that fails mid-storm means no pump at all when the water is highest.
- Flooding of the crawl space if the pump stops working entirely during sustained rain, which brings the standing-water consequences covered in standing water in a crawl space - wood decay, mold, and insulation damage - on a faster timeline than a slow drainage problem would.
- A higher repair bill than if it had been caught early. A pump replacement is a contained, predictable cost. A pump that failed during a storm and let the crawl space flood adds moisture-related cleanup and repair on top of it.
What you can check yourself
These checks are reasonable for most homeowners and take a few minutes:
- Watch a full cycle: does the pump clearly turn on, run, and shut off, or does it run continuously?
- Check whether the water level in the basin actually drops while the pump runs.
- Look at the discharge line outside the house - is water actually coming out where it should, or does the line look frozen, kinked, or blocked? Inside Seattle, the stormwater code allows uncontaminated water from crawl space pumps into the drainage system, but not into a sanitary sewer without Seattle Public Utilities' approval.
- Listen for grinding or a motor that sounds like it is working hard without moving water.
- If there is a battery backup, check that the battery itself is not the source of a false-running signal. Sealed AGM backup batteries are generally built for a 4-to-5-year service life, per the manufacturer's own specification for a common backup system - a battery well past that age is a reasonable thing to have checked on its own.
The best time for most of this is before the wet season rather than in the middle of it. The seasonal crawl space maintenance checklist builds a bucket test into its September-to-October pre-rain check — pour water into the basin and confirm the pump starts, discharges and shuts off — and a mid-winter check that the pump is cycling and the discharge is not frozen or backing up.
What this does not include: opening the pump housing, working on the electrical connection, or modifying the discharge line. Anyone you pay for that work has to be registered with the Washington Department of Labor & Industries (how to check), and a new circuit or receptacle for a pump needs an electrical permit, from the city in Seattle and several other cities here and from L&I elsewhere.
When to call a professional
Any of the warning signs above are worth a professional look, especially short-cycling or a motor that runs continuously without the water level dropping - both can damage the pump further the longer they continue. A contractor can also answer the question a homeowner usually cannot from the surface: whether the pump itself is the problem, or whether the drainage system feeding it is undersized for how much water actually reaches your house each winter. Those have different fixes at different prices, and a quote that assumes one without checking is a guess.
One local wrinkle is worth raising if you are in Seattle. The city identifies peat settlement-prone areas and says peat-rich soils settle when the groundwater table is lowered, which is what a pump that never stops is doing. If your property is in one, ask the contractor and the city's permit desk about it before adding pumping capacity.
Fixing it
Where the pump itself is the problem - failed motor, worn switch, damaged impeller - a sump pump replacement runs $1,600 to $3,125 on this site's modeled Seattle-metro range, before sales tax, with a battery backup pushing that toward the higher end. See the sump pump cost guide for the full breakdown of what is and is not included at each price point.
Where the actual issue is that too much water is reaching the basin for any pump to comfortably keep up with - the pump is working correctly but constantly - the fix is upstream: crawl space drainage that collects water at the foundation and manages it before it reaches the basin, running $4,025 to $7,175.
If you are not sure whether your pump needs replacing or your drainage needs upgrading, a free in-home inspection settles it before you spend on either - what that visit covers is worth reading first. You get a written, no-obligation quote; check that it says which problem it is pricing - the pump, or the volume of water reaching it - and, for a replacement, whether a battery backup is included, since that is what moves the price toward the top of the range.
Sources
Rainfall figures are NOAA's 1991–2020 normals for Seattle-Tacoma International Airport, as published in this site's climate and housing dataset. The perched-water pattern is Seattle's landslide study and USGS's southwest King County groundwater report; the discharge and peat points are the City of Seattle's. Equipment service-life and battery figures are the cited manufacturer and inspection-industry sources, not measurements of any specific pump - actual life depends heavily on how often a given pump is called on.
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International Association of Certified Home Inspectors (InterNACHI), InterNACHI's Standard Estimated Life Expectancy Chart for Homes Explanatory summary, not the governing text Checked
The two equipment service lives the ownership-cost model turns on: a dehumidifier at 8 years and a sump pump at 7 years. This is the chart the home-inspection trade actually works from, which is why it is cited — an inspector reading a service life into a report is most often reading this one.
Note: An industry guideline chart, not a measurement. It states its own figures are determined from research and testing under regular recommended maintenance and normal wear, and should be used as guidelines only rather than relied on as guarantees. It publishes no sample, no method and no confidence interval, and it is not specific to the Seattle area.
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Zoeller Pump Company, AGM Maintenance Free Battery — product specification Checked
That the sealed AGM battery for the Aquanot 507 and 508 backup systems is designed to deliver a useful life of 4 to 5 years — the figure behind the ownership model treating a backup pump’s battery as a recurring cost rather than a one-off purchase.
Note: A manufacturer’s design life for one battery type on one backup system. Actual life depends on how often the backup is called on, which in a Seattle-area crawl space is a function of the wet season and of the primary pump’s condition.
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NOAA National Centers for Environmental Information, U.S. Climate Normals (1991–2020) — Annual/Seasonal and Monthly (normals-annualseasonal-1991-2020, normals-monthly-1991-2020) Open dataset Checked
Every precipitation figure in the Seattle-metro climate and housing dataset: annual and monthly precipitation normals, the October–March total summed from the monthly normals, the average number of days per year at or above 0.10, 0.50 and 1.00 inches, and the completeness flag and years of record NCEI publishes alongside each value, for the eight stations within 15 miles of a served city with at least 20 years of record (Snoqualmie Falls, Landsburg, Monroe, Tacoma #1, Seattle-Tacoma International Airport, Seattle Sand Point, Renton Municipal Airport and Everett Snohomish County Airport). Pulled through the NCEI data access service on 2026-11-10.
Note: A normal is a 30-year statistic for one instrument at one point, not a value for the surrounding city. NCEI publishes a completeness flag with every value and this site republishes it, because a station with 20 years of record and one with 29 are not equally strong evidence. Seattle Boeing Field has 19 years behind its annual normal and is not published.
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Seattle Public Utilities (prepared by Shannon & Wilson), Seattle Landslide Study, Volume 1 Checked
That Vashon till, known locally as “hardpan”, is very dense and relatively impervious, so water soaking down through the deposits above it normally perches on top of it; that the contact between recessional outwash and till is normally less than 10 feet deep and the water perched there normally dries up in spring or summer and returns in winter; that the boundary where groundwater perches on the Lawton Clay is commonly termed “The Contact”; and that the study’s database holds 1,326 landslides reported through June 1999, records going back to 1890, about 84 percent with some human influence, landsliding in only about 1 percent of the city, and the highest densities in Southwest Magnolia, Southwest Queen Anne, Madrona, Interlaken and Alki.
Note: The PDF prints no date; 2000 is the year Seattle Public Utilities gives for it. A 2003 update added about 110 landslides; this site quotes the original figures.
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U.S. Geological Survey, Hydrogeology and quality of ground water in southwest King County, Washington (Water-Resources Investigations Report 92-4098) Checked
That across the southwest King County study area, which the report describes as including south Seattle, Renton, Kent, Auburn, Des Moines and Federal Way, till (“hardpan”) lies at the land surface over most of the area except the major valleys and averages about 60 feet thick; that many shallow wells in the till held water in winter but were nearly dry by late summer; and that the till plains have poorly drained stream courses and closed depressions holding lakes, wetlands and peat bogs.
Note: A regional groundwater study. It describes the till plains, not any city’s boundary or any lot.
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City of Seattle, Stormwater Code, Seattle Municipal Code Title 22, Subtitle VIII (July 2026 compilation; SMC 22.802.020 and 22.802.030) Checked
Where pumped crawl space water may go inside Seattle: SMC 22.802.020.B prohibits any discharge to a public or private drainage system that is not entirely stormwater, except as SMC 22.802.030 allows; SMC 22.802.030.B lists as permissible, unless the Director of Seattle Public Utilities finds a water quality problem, uncontaminated pumped groundwater, uncontaminated water from crawl space pumps, approved footing drains and other subsurface drains, and foundation drains; and SMC 22.802.030.C lets the Director approve drainage water to a sanitary sewer only case by case.
Note: The city’s own compilation, which it labels unofficial; the Seattle Municipal Code is the official text. These are City of Seattle rules. Every other city in the area has its own stormwater code, which this site has not read.
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Seattle Department of Construction and Inspections, Tip 325, Peat Settlement-Prone Areas Explanatory summary, not the governing text Checked
That peat-rich soils settle when they are loaded by structures or fill, or when the groundwater table is lowered.
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Washington State Department of Labor & Industries, Register as a Contractor Checked
That Washington requires every construction contractor to register with L&I and to be bonded and insured; that there are two classifications, general and specialty, with 63 specialties; that a specialty contractor works only in the registered specialty and cannot hire subcontractors; that plumbing, electrical, elevator, mobile home installation, boiler and asbestos work carry further education, examination and licensing requirements; the bond amounts ($30,000 general, $15,000 specialty); the liability insurance L&I asks for ($200,000 public liability and $50,000 property damage, or $250,000 combined single limit); that the bond and insurance must carry the exact business name; and that L&I suspends a registration when a bond or insurance policy lapses or a judgment goes unsatisfied.
Note: L&I’s page for contractors. The statute states the insurance minimums differently (RCW 18.27.050); this site gives both.
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Seattle Department of Construction and Inspections, Electrical Permit Checked
That in Seattle an electrical permit is needed whenever wiring is installed, altered, extended or connected to equipment, which covers a new receptacle or circuit for a sump pump or dehumidifier; that a professional applying needs a Washington electrical contractor’s license and a Seattle business license; and that owners may do their own electrical work on a property they own and occupy.
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Washington State Department of Labor and Industries, Electrical Permits, Fees and Inspections Checked
That electrical work in Washington requires a permit and inspection, with few exceptions (chapter 296-46B-901 WAC); that the permit is bought by the electrical contractor or by the property owner doing the work; and that L&I permits and inspects everywhere except the cities that run their own electrical program and Tacoma Power’s service area.
Note: Read 2026-11-10 for the regulatory dossier. Which jurisdiction permits a given address is confirmed with the Department of Revenue lookup L&I links.
Sources last checked between and ; the date beside each one is when it was last opened. Where a figure comes from a document that is revised on a schedule, the edition or version is named above so you can confirm it against the current one yourself.