A sump pump is an incredibly useful item to have in your basement: Unsophisticated but essential. It’s basically motorized pump in a bucket, buried below the floor of your basement or crawlspace; as the groundwater seeps up, it collects in the bucket, the pump activates, shoots it back outside, and your basement stays dry.
Sump pumps are designed to run intermittently on an as-needed basis, cycling on only when there’s enough water in the bucket. Though they will run constantly if your basement floods, in non-flood conditions, these “cycles” should be steady—if your sump is cycling on and off every few minutes (or even every few seconds) for a long period of time, especially when there doesn’t seem to be a reason for it, that’s a problem known as “short cycling.” Short cycling will wear out your pump, and most likely indicates a problem with your sump system. Here’s what to do if your sump pump short cycles or never stops running even though there doesn’t seem to be an issue with rising water.
Check the water levels
The first thing you should do is check the water levels in your sump bucket. Sump pumps are designed to trigger when the water level becomes a threat. But groundwater levels can change—one reason your sump will start cycling, for example, could be heavy rainfall that has raised the water table. Because water is sitting higher under your house, more of it seeps into the bucket, and your pump dutifully pumps it out.
If your sump is short cycling, head down to the basement. If the sump bucket is covered, uncover it. Disconnect the pump from its power source (typically this involves unplugging it from a nearby outlet) and observe what happens. If the water rises up in the bucket and begins to overflow, plug your pump back in and let it do its job. But if the water rises to a certain point and then stops rising, you might be dealing with groundwater levels that are higher than normal, but not flooding. There are several reasons this might be the case:
- Heavy rain. If your area has experienced a lot of rain, the groundwater might simply be high, keeping your sump busy.
- Snow melt. If your area saw a lot of snow that is now melting off, the ground might be saturated.
- Construction or leaks. If a water main is leaking in your area, the water levels under your house might be temporarily or artificially higher.
If the water level is high but doesn’t seem to be rising and you haven’t had any serious precipitation recently, call your local water authority to see if there might be a leak in your neighborhood. Check with your neighbors to see if they’re experiencing the same short cycles or if they have water in their basements. The water company may send a crew out to investigate.
Note: You should probably leave your sump pump on even if it’s short cycling. While short cycling will wear out your pump in the long run, shortening its lifespan, it’s better to deal with short cycling than take any chances with a sudden rise in water levels, even if you think you know what the cause is. A new pump will be a lot cheaper than a flooded house. Once the situation is resolved, your pump should return to normal operations.
If there’s no external situation causing your pump to short cycle, you’ll need to examine the system itself.
Check the float switch
Like a toilet, sump pumps are designed with a “float” that triggers the pump cycle. This is exactly what it sounds like: A plastic ball that floats on top of the water. When the water level in the bucket rises to a certain level, the float rises with it and triggers a switch that cycles the pump. When the float sinks back down as the water is pumped out, the switch disengages.
If your sump never stops cycling, examine the float switch. If it’s tangled in the power cord or debris, that’s an obvious solution to your problem. If it’s stuck in the “on” or “off” position, try loosening it with some WD40. If that doesn’t do the trick, you might need to replace the float switch. Unless you’re experienced with electronics and sump pumps, this is something you might need to call your plumber to take care of.
Examine the check valve
The check valve is a piece of plumbing magic that allows water to flow in only one direction. It will be found on the drain pipe leading up and away from the pump, and it simply prevents the water just pumped out of the pit from draining back into the pit after every cycle. If your check valve isn’t doing its job, your pump becomes Sisyphus, pumping the same water out of the bucket over and over again.
One clue you can look for is to study the sump bucket liner as the pump cycles. The liner should have several holes around the sides where groundwater seeps in. If you can see water flowing from these holes after every cycle, your check valve is probably not the culprit. If the water just seems to magically reappear, you should have your check valve inspected. Replacing a check valve probably involves calling a plumber.
Check the drain line
The pipe that your pump empties into might be clogged, frozen, or otherwise compromised. If the pump can’t push the water out of the house (into the sewer, or out into a properly graded back yard) it will wind up cycling constantly in a futile effort to clear the water. If the temperature is very cold, you might need to thaw out your pump’s drain pipe. Otherwise you might need to call a plumber to have the drain pipe inspected and cleaned out if necessary.
Finally, if your sump pump short cycles endlessly, you might have an over- or under-powered pump or liner. Sump pumps come with varying horsepower and capacity, and your pit and liner are designed to handle a certain volume of water. If your pump is too powerful, it will short cycle because it handles small amounts of water immediately; if it’s too small, it will run constantly because it can’t eliminate all the water present. And if your bucket liner is the wrong size you can face similar problems.
If you’ve looked at everything else and your sump is still short cycling, consult with a plumbing professional about the capacity of your system. If your sump system is old the water and drainage conditions around your property may have changed, requiring a sump update.