A submersible pump, as its name suggests, is capable of running underwater. This is one of the most versatile pump types on the market and is useful in a whole range of applications.

Like all pumps, there are many different types of submersibles to cope with a variety of applications. Because of the variety of pumps available, it is important that you understand the differences between them and the features you need to look out for when buying a submersible pump.

In this guide, we answer all the questions you have regarding pumps, such as: What is a submersible pump? How does a submersible pump work? And what is the best submersible pump brand?

What is Submersible Pump?

A submersible pump, also known as a sump pump, is a type of centrifugal (impeller operated) pump that can be operated when fully submerged underwater. Hermetically sealed to ensure the inner electrics are protected, a submersible pumps is either air or oil fuelled and can accommodate a range of impellers to tackle liquids and solids of different size and viscosity.

How does a Submersible Pump Work?

As mentioned above, a submersible pump is hermetically sealed to ensure the inner electrics are protected from the water. Useful in a variety of situations where you may want to remove unwanted bodies of water; a submersible pump works using a float switch to detect when water reaches a certain level. When the float switch detects the presence of water the motor within the pump is activated. This sucks the water up and into the pump, before being ejected out of the pump by the impellers.

Step 1 - Float switch detects the presence of water

Step 2 - Float switch operates the pump motor

Step 3 - Impellers draw water into the pump

Step 4 - Impellers force the water out of the pump and away from the home

Watch the video below for a full demonstration of how a submersible pump works.

What is a Submersible Pump Used For?

Submersible pumps can be used in a vast and varied number of applications. It’s one of the core reasons they can seem like such complicated pieces of equipment. Saying that, for the average person, a submersible pump will be used for one of the following three applications.


From efficiently watering the garden to clearing water from ponds and aquariums, the submersible pump is a key component of a thoroughly irrigated and healthy garden or piece of land. They are often implemented into rainwater harvesting systems as they can take the reliance off mains water and help people save money in the long term.

Pumping from wells and boreholes

The submersible pump is ideal for pumping water out of wells and boreholes. Efficient at pumping water up from great depths, the design of a submersible pump allows it to sit in tight or confined spaces and pump water without using too much power.

Draining Unwanted Bodies Water

A submersible pump is suitable for draining flood water and other unwanted bodies of water. Often situated in basements and other areas that experience frequent flooding, the automatic function on an electric submersible pump allows you to clear water without being present.

The Oil Industry

Probably not the main reason you are browsing this guide however, a submersible pump is a key tool in the process of pumping oil from ground deposits to treatment refineries.

Can Submersible Pumps Run Continuously?

Yes, you can run a submersible pump continuously for as long as you require if you have the suitable source of water. Saying that, it is imperative that you do not run a submersible pump dry. Running the majority of submersible pumps dry can cause significant damage to the inner motor and components. That’s why we recommend purchasing a sump pump with a float switch for automatic use.

The Different Types of Submersible Pumps

As mentioned at the beginning of this guide, there are many different types of submersible pumps. The two most common types are 1. Drainage submersible pumps and 2. Wastewater/sewage submersibles. Ultimately, the only difference between the two is the type of water or waste they can pump.

Drainage Submersible Pumps

The most common use for this type of pump is drainage. Manufacturers such as Grundfos and KSB produce this type of pump and they can be used for many different purposes. Most commonly they are used to clear excess water from cellars or basements that are prone to flooding. If you purchase this type of pump then please be aware that you need to pump the water to a safe and suitable location. You can also purchase a ‘lifting station’ which can safely discharge water away from the property and store the water in a tank.

Wastewater/Sewage Submersibles

When you plan to pump wastewater or sewage, you will need to consider purchasing something a little more heavy duty. The Calpeda GXCm 40b is the perfect dirty water pump. Pumps like these are suitable for applications where there are particles in the water, such as when emptying septic tanks or removing wastewater from industrial processes.

Choosing from the Various Submersible Pump Brands

Different brands offer a range of products capable of providing various solutions. Some are capable of tackling high viscosity liquids in short periods of time, while some submersibles are designed to be as efficient as possible over longer periods of time.


Grundfos is the largest pump brand in the UK. Offering a selection of innovative pumping technology, Grundfos is a trusted brand among engineers and offers carefully designed, well constructed pumps, albeit, at prices a little higher than their competitors.

Stuart Turner

Stuart Turner is an internationally recognised pump solutions provider and has an unprecedented reputation for product quality and innovation. Engineered to perfection, Stuart Turner submersibles offer power and reliability.


Offering engineering products for the manufacturing and industrial side of the pumping world, Calpeda is a pioneer in the development of heavy duty products that tackle the regular jobs other pumps can’t handle.


Another heavy duty brand, Lowara have developed one of the finest submersible pump selections on the market. Capable of handling high viscosity liquid and dirty water, Lowara pumps offer a heavy duty solution at a more than reasonable price.


KSB is one of the leading producers of pump technology and develops submersible pumps for both heavy duty and light duty requirements. Founded in Germany, you can expect quality engineering at an affordable price.

The Five Best Submersible Pumps

Submersible pumps can be used in a range of applications across commercial, industrial and domestic settings. From sewage treatment to oil wells, and from draining mine shafts to removing floodwater from a cellar, a submersible pump will make short work of an array of pumping requirements. To help you navigate the complex world of submersible pumps, we’ve suggested our five best submersible pumps, each of which is suitable for a different pumping application.

Grundfos Unilift KP 350-AV-1 Drainage Pump

The Unilift KP 350-AV-1 is the perfect pumping solution for purposes such as cellar drainage and dewatering of pools or liquid storage tanks.

Built to high-quality specifications with long-life stainless steel components and an automated safety cut-off switch, to prevent overheating in case of dry-running, this pump is a hardy tool that has many uses. The presence of a strainer at the base of the pump prevents fibres, particles and other debris from causing the pump to jam. This makes it perfect for dirty water applications.

Search prices on the Grundfos Unilift KP 350-AV-1 Drainage Pump here.

Stuart Turner Supervort Drainage Pump

An excellent choice for general-purpose, low-intensity applications, the Supervort drainage system is best suited for rainwater harvesting or in ponds with large gravity-fed filters.

Pump control is automated through the included adjustable float switch. They are not suitable for sewage-handling, though, making them a good budget choice for domestic consumers.

Search prices on the Stuart Turner Supervort Drainage Pump. 

Calpeda GXC/GXV Sewage Submersible Pumps

For sewage and dirty water applications, the Calpeda GXCm submersible system will get the job done.

The design means it’s suitable for use in liquid containing solids up to a huge 35mm in diameter and it incorporates smooth stainless steel surfaces for easy cleaning.

Available for 240v or 415v outlets and with two-passage impellers or free-flow vortex impellers, their flexibility is unrivalled.

Search prices on the Calpeda GXC Sewage Submersible Pumps here.

Wilo-Drain Emergency Pumping Kit

One of the most common uses of submersibles is to drain floodwater. This emergency flood kit boasts a Wilo-Drain TMW water-cooled 240v drainage pump and a 10-metre hose.

This kit is guaranteed to make the difficult situation of a flooded house much easier to deal with. It includes additional accessories such as a cage basket for filtering debris and leaves.

The kit has many great aspects and it is very affordable, making it a must-have pump, even simply as an emergency stand-by for households in areas with a high risk of flooding.

Search prices on the Wilo Drain Emergency Pumping Kit here.

Calpeda GEO230 Pump Lifting Station

For serious pump users, the Calpeda GEO230 submersible pump lifting station provides a 230-litre capacity tank solution for use with the Calpeda GXVM/GQSM range of drainage pumps.

The automatic collecting and lifting station is suitable for both clean and waste water, depending on the pump used. The stainless steel construction allows for a long service life and makes the device easy to clean.

The advanced technology employed gives a maximum flow of 36m3 per hour. An added advantage of this pumping station is that it is often possible to install alternative pumps to meet specific requirements if necessary.

Search Prices on the Calpeda GEO230 Pump Lifting Station here.

How to Select the Right Submersible Pump

Replacing a submersible pump may seem like a difficult and complicated task, but if you follow the tips below then you should be sorted in no time.

Take a Look at the Old Pump

If you’re replacing a broken submersible pump, then take a look over the old installation. Firstly, the old pump should have a label that details the specification of the pump. This should make it easier to decipher which pump type you need when browsing online. Another component to note down is the size diameter of the discharge pipe. Make sure to check that the pump you’re buying online is the same size and shape.

Choosing the Right Float Switch

A common mistake is buying the wrong type of float switch. There are two types available. They are:

Vertical Switch Pump - this switch activates the pump by moving straight up. Often used in smaller pumps, this float can be used in smaller 10-inch diameter submersible pumps.

Tethered Switch Pump - this switch activates the pump by moving in a diagonal direction upwards. Only available in pumps with a 14 inch (or above) intake, these floats are often used in heavy duty submersible pumps.

Battery Backup System

Submersible pumps are often used in an attempt to protect homes from flooding. If you do intend to leave a submersible pump running during a flood, just remember that electricity may be cut from your home at any time. If this is the case, make sure you purchase a pump with a backup battery system. A backup system simply offers peace of mind. Can you imagine how it would feel to return home after a flooding event to find that your pump ran out of power?

Consider the Pumping Distance

Submersible pumps will come in all different shapes and sizes. One of the key differentiators is the power capability of each pump. Consider how far you want to pump liquid. The further you want to pump the liquid, the more powerful you will want the pump to be.

Consider the Viscosity of the Liquid

In the same vein, consider the viscosity of the liquid you intend to pump. The thicker the liquid, the more difficult it will be to pump. Thin liquids like clean water will be relatively ok with a low power pump. But if you intend to pump dirty water then you will need a pump with a lot more power.

A Few Final Dos & Don’ts of Buying a Submersible Pump

Before buying and using a pump, take a look over these Dos and Don’ts. Most will be common sense, but a few will ensure your pump stays in full working order. On a further note, please take the time to thoroughly read the installation and operation manual provided with each pump.


Check the Pump isn’t Damaged Prior to Use

If you’re buying second hand or renting a submersible pump, please take the time to ensure the pump is not damaged prior to use. Take extra time to ensure cables are not frayed.

Connect to an Appropriate Power Supply

If you intend to use the pump during a flood event, please make sure that you connect to an appropriate power supply. Ensure the power supply is well away from floodwater.

Make a note of the Pump Type before Fitting in Sump

If the pump fails while underwater, you will thank your lucky stars that you noted down the pump type and model.

Make sure the Float Switch can Move Unrestricted

The main cause of submersible pump failure is the pump running dry. This is often caused by a faulty float switch.

Make sure the Pump Filter is Cleaned Regularly

Once a month make sure you take the pump filter apart and give it good clean. This will keep your pump in full working order.


Lower the Pump Down with the Power Cable

If the power cable frays when lowering the pump down then you are guaranteed to break the pump. Electricity and water do not mix. Take the time and care to lower the pump down and secure in place.

Allow Water to Freeze around the Pump

When water freezes it expands. If the water freezes inside of the pump it could damage the inner workings of the pump.

Leave the Top of the Sump Open or Uncovered

A submersible pump is only hermetically sealed if the whole of the pump is correctly closed and covered.

Allow the Pump to Run Dry

The most important thing to not do is let the pump run dry. Submersibles are designed to pump water at all times and must have a suitable water supply. Purchase a submersible with a float switch to ensure automatic cut off.