Why Does Sump Pump Run When It’s Not Raining?

If you have a sump pump, then you will know it is supposed to work when there is so much rainfall that it seeps underground and could potentially cause flooding to your basement or crawl space.

Whilst it is normal to hear it kick in as the rain gets heavier, it is not normal to hear its familiar sounds when it is sunny and dry.

So, why does a sump pump switch on when it shouldn’t be? In this article we shall look at the reasons why, and how you can prevent it from happening.


Why Does My Sump Pump Run Even Though It Is Not Raining?

If your sump pump is working but there is no rain in sight, then it could mean that there is a problem. However, having said that, although strange, your sump pump might even be working correctly.

To understand whether it is a fault or that your sump pump is doing exactly what it is supposed to, we have put together a list of reasons why it may be working despite no rain. 

Reasons Your Sump Pump Is Running Despite No Rain

Below we have put together a quick list of reasons as to why your sump pump may be working even though there is no rain in sight:

Melting Snow

Whilst a sump pump is known for keeping the rain out, melting snow can also cause it to begin working.

If it has recently been snowing and the temperature has changed to above freezing, then there is a good chance that the snow is now melting.

When this happens, it’ll turn straight into water and move its way underground.

Whilst some of the water will become absorbed by various things such as the soil and plants, you may find that there is too much water.

So instead of it all being taken up by nature, it will reach the sump pump, meaning it will activate to prevent your underground space from flooding. 

Increased Amount Of Water In The Ground

If it hasn’t been snowing, then there is a much more common reason: an increased amount of water underground. Whilst you might think this only happens via rainfall, it isn’t quite true.

This is because you can get an increased amount of water in the ground due to lakes and rivers – or even broken water pipes in the area. 

You might not know this is happening due to it being impossible to even detect the increase of underground water near your home. This means the sump pump will turn on, despite there being no rain.

If you suspect this is happening, and it doesn’t happen too often (so it isn’t a recurring fault), then search online to see if there are any local burst pipes, etc. 

Float Switch Has Broken

How Do I Know How Much Water Is Coming Out Of My Sump Pit

If you find that your sump pump is running, and maybe even still running, then there is a good chance that the float switch has broken. This can happen when it becomes stuck in an ‘up’ position.

When this happens, it means the float switch does easily fall and rise as the water levels change. This means it has no idea when to turn off, so it will constantly run, even when there is no water to remove. 

Usually, you can fix this yourself by changing the switch yourself, or spraying it with some WD-40 to get it moving again. 

If you cannot fix the situation, then it might mean that you will need to buy a brand new valve, or even a pump. 

Drain Has Clogged

If you have clogged drains, then no matter what kind of sump pump you have, the water will struggle to drain.

Just as expected, as time passes, there may be bits of debris and tiny particles which find their way into the drains.

When the water is unable to pass through the drains due to clogging, it will hang around in the basin of the sump pump. This obviously isn’t ideal, because it means it cannot efficiently do its job – if at all!

If this lasts for a while, it may soon start to overheat and keep running. This can cause it to malfunction, and you might even see smoke.

If left, it will soon overflow and cause it to do the exact opposite of what you need the sump pump for – it’ll flood the basement. 

Pump Isn’t Draining

If your pump isn’t draining water away from the pit, then there could be either an electrical or mechanical reason as to why it is doing so, as well as the sump pump running without rain due to this very issue.

To determine if this is what is happening, add some water to the pit area to watch the float switch raise up to ‘on’.

If the pump then starts to run but the water is not going down, then the problem may be the drain system or pump. 

When It’s Raining, How Often Should A Sump Pump Run?

Depending on whether you have a weak pump, or how much rainfall there is, a standard sump pump should be running every 15 to 20 seconds.

If there has been heavy rain, you will find that it runs constantly for a while due to the rising level of water underneath your home. 

Final Thoughts

Your sump pump is a very important part of maintaining your home and preventing floods. Without it, you could end up with some very expensive water damage to deal with.

However, regular maintenance is essential to keeping your sump pump in good condition.

If you find that your sump pump is working even though it isn’t raining, then it could cause an alarm.

Having said that, whilst you might think that your pump is broken, it could just mean that it is doing its job properly.

Hopefully, the points above will help you to determine what the issue is – whether your sump pump is taking up melting snow water, has a clogged rain, or it needs a new valve. 



Bill is a DIY plumber, handyman, and homeowner with more than a decade of experience. He has replaced and repaired sump pumps, backup pumps, float switches, check valves, and many other things around his family home. An engineer and tinkerer at heart, he is always looking to see how things work and taking on new home projects that help him grow his skillsets. He is a husband and father of two boys, has a bachelors degree in Computer Engineer and minor in Mathematics and likes to make homebrew beer in his free time.

      Sump Pump Advisor