How Sump Pumps Work

If you’ve ever been curious as to how a sump pump works, then wonder no longer! We are going to tell you everything you need to know about sump pumps. They’re one of those things in your home you may not have thought a ton about but are actually very important.

Or maybe you just had a small flood and now people are telling you that you should’ve had a sump pump! You just nodded and smiled politely but deep down had no idea what a sump pump is.

Let us tell you.

So, What is a Sump Pump?

We’re glad you asked! Before getting into the nitty-gritty details, let just go over a few basics.

  • A sump pump’s sole job is to keep basements from flooding. More than just keeping them from flooding, it helps to keep the area under the building dry in general.
  • Sump pumps are located in the very lowest part of the basement or in a crawl space. The reason why this will all make sense later.
  • In addition to being in the lowest part of your basement, they are installed in a special ‘sump pit’.
  • A lot of homes across the United States are susceptible to flooding and even a slightly moist basement can actually cause a lot of issues, even if it’s not flooded.
  • They’ve become so popular in recent days that in a lot of areas, they’re actually required to have. Even if this home is new or not necessarily susceptible to flooding.

What Do They Do Exactly?

This is what happens:

  1. Water flows into the sump pit, either through drains or just water flowing in naturally through the soil after heavy rains.
  2. The sensor on the sump pump is triggered and the sump pump is automatically activated.
  3. The pump then begins to take this excess water in the sump pit and pump it away from the house so that it doesn’t flood!
  4. Voila! Your basement is saved from flooding.

The Details

Okay cool, we now have a basic understanding as to how these sump pumps work and what they do exactly. Now let’s get into the details of what exactly is going on.

  • Sump pumps really are not that big. As we mentioned, it’s always in a put and always in the lowest part of your basement or crawlspace. This pit isn’t very large, however.
    • The pit itself is only about two feet deep and 18 inches wide and in general, is surrounded by gravel.
  • The water flows up and away from the house, at least 20 feet away from the foundation actually.

  • The pipe also usually has something called a chuck valve at the end of the pipe. This is a small valve that’s meant to keep water from flowing back into the pipe.
  • We mentioned before but automatic sump pumps are activated by a pressure sensor
    • When it senses that water is exerting more pressure on the sensor than the air is, the pump will activate and start pumping out that water.
    • You can also purchase manual pumps that will only turn on when you run them! This obviously isn’t as convenient as an automatic pump because you may not know exactly when you need to turn it on.
      • The main benefit of a manual pump is that they’re generally cheaper.
    • Automatic pumps are nice because there is usually an option for you to turn it on manually, should the sensor stop working or if you just want to test it.

How Does the Water Actually Get Pumped Out?

Well obviously it gets ‘pumped’ out, but what does that mean exactly? It has a little to do with physics.

The most common pump used is a centrifugal pump. There’s a fan-like device that starts spinning extremely fast and using the centrifugal force created, it pushes all the water towards the side of the pipes which creates a low-pressure area at the center.

Once this area is created, water from the pit then flows into the empty center and the spinning action will then push all the water straight through the pipe and out to the great outdoors! Easy as that.

Sump pumps are super easy to set up as well. They just run on electricity so there’s no special wiring or anything that you have to do. You simply have to plug it into a grounded outlet and you’re good to go!

Since it’s going to be in/near water almost all the time, we also recommend that you use a GFCI outlet. GFCI outlets are meant to be used when something needs to be plugged in around/near water. It just makes it a little bit safer.

Different Types of Sump Pumps

There are actually two different types of sump pumps that you can install! There is one that is much more common/popular than the other, but we thought we’d let you know about both just in case.

So what are they and what are the differences between the two?

Submersible Pump

The submersible sump pump is definitely the most common. It rests in the water and is encased in a waterproof housing. The pump itself is at the bottom and the outlet pipe is of course, near the top.

There is also a grate that covers the bottom of the pump to help keep out any dirt and debris. Once the pump is turned on, water is sucked through the grate, routed through the pipes, and then out of your home.

Yay! Easy as that.

Pedestal Pump

These are slightly less common and have a very interesting design. They look sort of like a really long baseball bat with a fat head at the top.

The pedestal helps to keep the actual pump out of the water, even when the pit is entirely full. A pipe reaches all the way down to the bottom of the pit to get the water out and pump it out from the basement.

Since the motor and the pump are completely out of the water, this is going to make the pump significantly louder than a submersible pump.

However, if you’re looking to save a bit of cash, they are generally much cheaper than a submersible pump.

Different Factors for Choosing a Sump Pump

Manual v. Automatic

We talked about the differences a bit before. There are really only a couple of main differences. A manual pump is going to be slightly less pricey, but overall an automatic pump is going to do a better job and be much more convenient.

If you live in a place where you’ll need it a lot, we recommend the automatic pump.


Horsepower generally ranges between one-quarter and one-third horsepower. Obviously, the more horsepower that a sump pump has, the faster it will pump out the water.

Not everybody will need one with a lot of horsepower so if you don’t need it, don’t waste the money.

Head Pressure

This refers to the height that a pump can raise water. How much head pressure you need will ultimately depend on exactly how deep your basement is.

For example, if the head pressure is only 10 feet, you need to make sure that you don’t place your sump pump deeper than that.

Cord Length

The last thing that you need to consider, which may sound silly, is the cord length. Obviously, you’re going to need to plug your sump pump in. But the thing is, you should plug it directly into an outlet and not an extension cord so it’s going to need to reach.

Do I Even Need a Sump Pump

Good question! It’s always safer to have one installed, especially considering they’re not that expensive. With that being said, if you do live in a super hot/dry area such as the Southwest ( of the United States), you might not need one.

One little note, if your basement does have moisture and no sump pump yet, the first step in dealing with the moisture is to first run a dehumidifier to get all the excess moisture out and then install the sump pump.

Sump pumps greatly help. We have a guide on how to clean a septic tank, take some time to read it here.


There you have it! Everything you need to know about sump pumps. You should be an expert by now.

Go forth and impress your friends with your newfound knowledge.

Justin Howe

Electrician and DIY specialist Justin deleted his own successful tech blog to write expert product reviews and buying guides together with his friend Robert.

Justin Howe

Electrician and DIY specialist Justin deleted his own successful tech blog to write expert product reviews and buying guides together with his friend Robert.