Best Pumps for Excess Water & Flooding

Key Terms & Concepts

You don't need to know everything about pumps in order to find the right one for your situation. Understanding a handful of terms and concepts is all it should take to make a quality purchase, whatever type of pump you're after.

• Total Dynamic Head (TDH, often just called "head") refers to the distance the pump can move water. Head is calculated by adding the "static head" (vertical distance the water travels from pump intake to the highest point of the discharge pipe), to the "friction loss" water experiences as it travels through the discharge pipe. Friction loss takes into account the length of discharge pipe (including any horizontal "run") and the number and type of directional fittings (like elbows) along the line. Static head + friction loss = total dynamic head.
  • To calculate friction loss, you'll need to know the diameter and length of horizontal pipe you'll be using, as well as the number and type of fittings in the line. You can use one of the many calculators found online, or go old-school and consult our friction loss charts.
  • First, determine the "equivalent length of pipe" from any fittings used in your discharge line. Use the second chart on our friction loss page to find the equivalent length for the type and size of fittings used in the line. Add this to the actual horizontal run of pipe (easily obtained via tape measure, or memory).
  • System capacity is the volume of water that flows into a sump pit - it tells you how much water needs to be pumped out per minute to prevent flooding. Knowing your system's capacity will give you the most accurate idea of the friction loss experienced in your discharge piping. Unfortunately, determining it is (often) an impractical chore: you need to wait for moderately heavy rain. Using a ruler and a stopwatch, you'd measure the height of water collected in the pit in one minute, and derive the system capacity in gallons per minute (in an 18" sump pit, 1" of water = 1 gallon. In a 24" pit, 1" = 2 gallons).
  • The above method will provide you with the best information for the wisest purchase. However, you can ballpark the system capacity: in a home built on sandy soil, assume 14 gpm per 1000 sq. ft.; on clay soil, assume 8 gpm per 1000 sq. ft.
  • Find your flow rate (GPM) and your pipe diameter on our friction loss chart - this will give you the number of feet lost to friction per 100 feet of pipe (your "multiplier"). To calculate the total friction loss, use this formula: Horizontal pipe length + equivalent length of pipe × friction loss multiplier / 100 Add this to the static head for your TDH.
• Calculating the total dynamic head may seem like overkill, but it's important because it will help ensure that you select the best-performing pump for your situation. TDH is the y-axis of a pump's performance curve chart - one of the most important things to look at on the pump's listing or packaging. This chart graphs the performance of the pump across its operable range: the rate of discharge at a given head. Find your total dynamic head on the vertical y-axis, then find the corresponding point on the horizontal x-axis - this tells you how quickly the pump will clear out water in your specific situation. You'll want to select the pump with the highest flow rate at your TDH.
• Many assume that a pump's horsepower rating is the primary concern when choosing between models, but it's actually more of a secondary one - the pump's performance curve will give you a much better idea of what to expect. While it is true that a pump with higher horsepower will pump more water a greater distance, what you should be concerned with is how much/far you need to pump. These (and most other) pumps operate at a fixed-speed, so a pump that has more power than is necessary for the situation will use more energy, cycle more often, and ultimately burn out the motor. The vast majority of residential applications will be satisfied with 1/3 or 1/2 horsepower.
• Float switches and controllers are used to turn pumps on and off, so you don't have to. Automatic pumps (like sump pumps) will have a float switch already built-in - manual/non-automatic pumps can have one added on.
  • There are two types of float switch: tethered and vertical. Tethered switches resemble the float ball found in older toilets, and are in fact tethered to the pump. They require a sump pit at least 14" in diameter, otherwise they may not function properly and could even get stuck. This makes them a better choice for larger pits, where they can keep pump cycling to a minimum, extending the life of the pump.
  • On a vertical switch, the float is connected to a straight, rigid arm. Water in the pit pushes the float up to activate; when the water level falls so too does the float, turning the pump off. These switches are best for narrow or shallow sump pits.
  • Controllers are an electronic variation on the float switch, and allow you to precisely control on and off water levels - this can be helpful with large pits or when it's impractical to drain the entire pit at once. Because they have no moving parts, controller switches are typically more reliable than their mechanical predecessors.
• Check valves are an integral part of pump systems. These are one-way valves that prevent discharge water from flowing back into the pump, which would keep it running and eventually wear it out. Most pumps will ship with a check valve for you to install on the discharge line just above the pump. If yours doesn't, we have several types that will work for you.
• Pumps are typically constructed using cast iron or thermoplastics. The latter are usually less expensive, but are still considered to be fairly durable. Stainless steel pumps are also available, and in addition to the trusted strength of metal, have the added benefit of greater corrosion resistance.
• Don't forget to check the breaker for the circuit the pump will be on. The breaker should note the maximum amperage directly on the handle - make sure that the amperage of the pump (and any other devices on the circuit) does not exceed the breaker rating. If the electrical draw is too great you'll need to upgrade the breaker or find a different pump.

Types of Dewatering Pumps

Sump Pumps

• Sump pumps are the standard for basement protection. These pumps need to be situated in a pit - the sump, or basin - that's set in the lowest point in the ground. When water fills the pit to a certain level (determined by the float switch or controller), the pump activates and moves water out. The pump turns off when the water level falls below a set threshold.
• When should you have a sump pump? If you live in an area that experiences annual heavy rains and have a basement - even an unfinished one - it's one of the simplest things you can do to protect your house and provide peace of mind. Washing machine in the basement? Sump pumps are the best defense against busted supply hoses and sensors that fail to stop the fill cycle. Split-level homes (where family areas are located partially below ground) and houses that sit low atop a high water table are also more susceptible to flooding, and should have a pump system installed.
• Sump pumps need to sit in a basin or pit (the sump) set in the ground, into which excess water will collect. These pits are typically at least 22 inches deep with a diameter of 18-24 inches. A plastic liner or basin is used to provide the pit with structural integrity. An 18" sump pit will suffice for most residential applications, but keep in mind that a smaller pit means more pumping, which will shorten the pump's life. Submersible sump pumps will need a larger pit than pedestal pumps.
• Submersible sump pumps are the most popular type of pump for the home. A sealed housing allows the entire unit to stay submerged in the sump pit, where it has the benefit of being cooled by the water that surrounds it (a big plus when pumping for extended periods). Because they're fully immersed while running, motor noise is significantly reduced as well. Many submersibles require some water to be in the pump at all times for lubrication, so it is important to have the float switch set properly to avoid the pit becoming totally empty.
• Pedestal sump pumps are tall and skinny, with their impeller submerged in the pit and the motor staying dry well above. Their design is perfect for smaller diameter pits. Since the motor doesn't have the benefit of being in water while running, pedestal pumps are noisier than their submersible counterparts, making them a less than ideal choice for finished basements, or areas with poor sound insulation. Being out of the water does typically make them easier to repair, however.
• Where does all the discharge water end up? In days past, a sump discharge could drain into the sewer system, but this is no longer permitted in most areas. Instead, water is usually directed as far away from the structure as possible (at least 10 feet) to an area with good slope and drainage, where it will soak into the ground.
• Some sump pumps can be installed outdoors to prevent landscape flooding - a perfect solution for low-lying areas of the yard that quickly become lakes when rains come, or yards with bad grading that deposit water around the home's foundation. While a sump pump will help with these problems, you might also look into correcting the slope of the yard and/or constructing a French drain to carry water away.

Our Top Submersible Sump Pumps

Little Giant 6-CIA

DuraMAC 5033PVSP

Zoeller M53

Our Top Pedestal Sump Pumps

DuraMAC 5033PVPD

DuraMAC 5050CVPD

Zoeller M82

Backup Pumps

• Investing in a quality sump pump is an important part of owning a home in flood-prone territory. Equally important is investing in a backup for that primary pump. However good the primary pump is, there's always a chance the pump will fail, or the power will go out. Some may be willing to risk water damage and lost possessions in the belief that their highly-rated, long-warrantied unit will always work so long as they have a generator, but this is a strategy we cannot endorse - the cost is simply too high.
• Backup pumps are designed to kick in when the primary pump stops working. They're installed above or next to the primary in the sump pit, and can be battery or water-powered. Some models include the ability to sound alarms when activated, connect to an auto-dialer, or even send alerts to your phone so you know when something is up.
• Water-powered backup pumps are connected to the municipal water supply (they are not for use with wells). They rely on the physics of fluids to create suction using the flow of water through the pump. These pumps typically use 1 gallon of city water (at a minimum pressure of 20-40 psi) for every 2 gallons of sump water pumped out, and are not as powerful as battery pumps. Be aware that some places have prohibited the use of water-powered pumps (often due to water use restrictions), so check with local authorities before buying.
  • In-sump water pumps that live in the pit are often required by code to be accompanied by an RPZ (Reduced Pressure Zone) backflow preventer so your clean water supply can't be tainted with dirty sump water. An RPZ can be pricey, so be sure to factor this into your budget.
  • Above-sump backups are usually installed on the ceiling above the sump pit, removing most of the backflow risk; these will not often require an RPZ but may require a less-expensive vacuum breaker in some areas.
• Battery-powered pumps are typically 12V, and usually use marine or AGM (Absorption Glass Mat) batteries. The battery housing sits outside the pit, and the pump is connected to the primary pump's discharge pipe by way of a tee (though some can be installed independently with their own discharge). Some batteries will require regular maintenance (like adding distilled water) and all will need to be replaced at some point - so you'll need to stay on top of things to ensure protection.

Our Top Backup Pumps

Liberty SumpJet

Little Giant Battery Backup

Zoeller Aquanot

Utility Pumps

• Utility pumps are portable, multi-purpose dewatering pumps. These are the pumps for everyone who doesn't have a basement or other serious flooding concern (though they can be suitable backups), but still wants to be prepared for the occasional drainage issue, random burst pipe, busted washing machine, or freak storm. They're also used in routine applications like draining a water heater or keeping pool covers clear.
• Utility pumps will run off household electricity, batteries, or even gas. They can be submersible, with the intake at the bottom of the unit - or they can be non-submersible, in which case a length of hose or pipe is used for the intake. Most utility pumps are designed to be manually operated, and so do not come with float switches.

Our Top Utility Pumps

Little Giant 5-ASP

DuraMAC 5020PUUP

Zoeller 44

Pumps really are remarkable things - they turn nature on its head by making water run uphill, and can single handedly save a building - but they should never be the only line of defense against water damage.

• Make sure the yard has suitable drainage and slope to prevent water intrusion around the home's foundation.
• Regularly clean and inspect rain gutters to remove another potential source of flooding around the foundation.
• Regularly inspect washing machine supply hoses for wear, and replace with braided stainless steel supplies. Consider installing a flood prevention device that can alert you or even shut off the water in the event of a hose break or machine failure.
• Keep an eye on other water-using appliances like water heaters and dishwashers. Water alarms and flood prevention devices will provide protection and peace of mind, especially those that can automatically shut off water supplies before flooding gets out of hand.