It’s a nightmare every homeowner dreads: The basement flooded, belongings waterlogged. Carpeting and wallboard ruined and waterlogged.
While a comprehensive waterproofing and drainage system has many components, sump pumps are considered the most crucial. Unlike the membranes, drainage sheets, and perforated pipe, which usually last for the life of the structure, sump pumps need to be replaced every few years.
But waiting for failure isn’t an option, as it might inevitably lead to the nightmare described above.
Fortunately, new pump technologies and appropriate installation can ensure that this critical piece of the system is fail-safe and reasonably priced.
All sump pump systems have the same five components, although they vary in size based on the amount of water they are required to handle.
In the United States, separate pieces are fairly consistent. For residential applications, they consist of:
1. A plastic or metal sump liner, either 18 or 24 inches in diameter and 2 to 3 feet deep.
2. A pump, usually 1/3 or 1/2 horsepower and powered by either at 12-volt DC battery or standard 120-volt AC current.
3. A discharge pipe, typically 1 1/2 inch PVC.
4. A check valve to make sure the water in the discharge pipe doesn’t flow backwards again into the sump;
5. A cover to keep vermin, pets, and debris out of the sump.
Pump Size: A properly sized pump is significant. Too small and it won’t be able to keep up with water flowing into the sump. Too large and it creates unnecessary expense. An oversized pump will also “short-cycle,” turning on and off in rapid succession, which leads to premature pump failure. So getting the right pump is an essential first step to ensuring basements stay dry.
“It’s important that your pump can draw water out of the basin (or “sump pit”) faster than water flows into it,” notes Duane Friend, at the University of Illinois Extension Office. “Therefore, the first thing you need to compute is the amount of water that drains into the basin during a high-flow period. During a heavy rain, stick a ruler in the basin and measure how many inches of water flow into the basin in 60 seconds.”
With an 18-inch sump, each inch of deepness equals one gallon. In a 24-inch-diameter basin, each inch is roughly 2 gallons.
In a new construction site, approximate flow rates can be calculated based on rainfall averages, soil type and the size of a home’s footprint.
Once the volume of water that will need to be removed has been calculated, the installer will have to to figure out the “total dynamic head” of the discharge pipe. This is the totting up of the “static head” (the height in feet between the pump and the end of the discharge pipe) and the “friction head.” Friction head is sized based on the length, diameter and material of the discharge pipe, and the number of turns involved. A table to calculate friction head is available on the www.waterproofmag.com website.
Knowing the maximum flow rate figures, the total dynamic head pressure involved, and the budget, the contractor or designer could maybe determine the best pump for the application.
Basin Size: The size of the sump pit is also significant, as it plays a part in how long the pump runs and the time it takes to fill up. If the basin fills too quickly it may be best to install a larger one.
If the basement is already finished, a cheaper option may be to raise the height of the pump switch, basically making the sump deeper. This technique, however, also increases the chances the sump will overflow, so be careful.
Direct-Wired: Almost all sump pumps run on standard 120 volt AC current, but the pump should be supplied with its own line from the breaker box. It must also have a dedicated breaker. In most areas, the power supply must be installed by a licensed electrician unless the installer is also the homeowner. As always, check with community building codes and ordinances.
Pumps are usually hard wired into the electrical system, rather than plugged into a conventional outlet.
Battery-Powered: Sump pumps face their highest loads during thunderstorms, when rainwater pours into the sump pit from the foundation drainage method. Unfortunately, thunderstorms would also disrupt a home’s power supply, making the pump offline at the time it is needed most. That’s why some homes—especially those with finished basements—have a second battery-powered sump pump in case the first pump fails. In a few areas of the country, which the sump pit only fills sporadically, battery-operated pumps are presented as the primary.
The SmartHome sump pump is a next-generation battery-operated sump pump. It is self-testing, self-diagnosing, and will immediately notify the owner by telephone and email if a component stops working.
Setting up a battery-powered secondary pump involves purchasing and installing the following components in parallel with the others:
A 12-volt DC sump pump matching the flow and discharge requirements of the main pump.
A 12-volt DC lead-acid battery. A typical automobile battery is adequate. Some use marine-grade deep cycle batteries that are more costly, but lasts longer.
A “trickle-charge” battery charger to keep the lead acid battery fully charged.
A separate water level sensor, check valve, and other components. The discharge pipes usually connect downstream of the check valves.
“One of the problems with most backup sump systems is they are rarely used so a component failure will not be noticed and the system will fail to operate when needed,” says Friend.
A few battery-powered pump systems hold an integral computer that tests the system occasionally and sounds an alarm if something needs to be replaced—like a “check engine” light on a car.
Regardless, Friend recommends that backup systems be tested monthly. “A good time to test is just after a rain storm,” he says. “Pull the plug on the sump pump so the sump well fills and make sure the backup system activates and empties the well.”
Water-Driven: Recently, a few manufacturers have begun offering sump pumps that use the home’s culinary water supply to power the pump. The pressure in the home’s main water line turns an impellor, which drives the pump. These devices abolish the need for electricity entirely. They do cost more than motor-driven pumps, but because they don’t need a back-up pump, they can be cost-effective.
Regardless of the type of pump installed, plan on also using a simple battery-powered water alarm. The water sensor is attached to the sump liner a few inches below floor level and will sound a shrill alarm if the water level rises that high up.
The discharge pipe should finish as far from the house as possible. Here, it has been routed to a dry well, with perforated pipe and gravel to improve drainage.
Since pedestal pumps sit above floor level, they are usually hidden from sight in finished off basements. This can be a purpose-built enclosure, or by building the sump in a closet or furnace room.
Regardless of the type of power supply, sump pumps are generally divided into two classifications, pedestal and submersible.
Pedestal pumps are mounted on top of the pit, where it is more easily serviced, but also more conspicuous. Submersible pumps sit inside the sump—usually near the bottom—and are completely immersed in the water.
The decision is usually based on whether the basement is remodeled, or will be, as the submersible pump is less obtrusive.
In commercial applications, submersible pumps are generally common, as they funtion on a different principle. Unlike pedestal pumps that “suck” water up from the sump like soda thorugh a straw, submersible pumps “push” water up the pipe.
The discharge pipe should end as far from the house as possible, to prevent the water from getting it’s way back underneath the foundation.
In decades past, the pipe was often connected to the sanitary sewer routine. This practice is now outlawed as it can overwhelm the water treatment facilities. Be aware that if you are retrofitting an older home, codes and ordinances may oblige you to also reroute the discharge line.