Can you count on your sump pump?
A sump pump is one of the
most important (and most
ignored) disaster prevention
devices in a home. When this
simple system fails, the results
can be catastrophic, leading to
thousands of dollars in
damage, daily disruptions
caused by major repair work
and higher insurance premiums
for years to come. So spending
some time and money on
avoiding failure makes a lot of
Some homeowners keep a replacement pump on hand in case their pump dies. That's a good idea (home centers often sell out of
pumps during storms or floods). But having a replacement handy won't help you if you're on vacation during a power outage or if your
pump dies while you're slumbering through a stormy night. That's the beauty of sump pump backup systems: No matter what the reason for the
pump failure, a backup system will save the day. In this article we'll show
you the options.
What causes primary pumps to fail?
The most common reason for pump failure is a power outage, not some problem with
the pump itself. Common events besides power outages can also cut off the supply of
electricity. For example, lightning can trip GFCI outlets, or someone can unplug the
pump and forget to plug it back in.
Assuming the power stays on, sometimes the pump itself fails. Many inexpensive
sump pumps are simply too small to handle the flow from a major downpour or rapid
snowmelt. And because inexpensive pumps are built with less durable materials, they
lose pumping efficiency. So the pump runs more often and burns out early. Or the motor
runs but the pump doesn't eject water.
Float switches are also a frequent cause of pump failure. “Wide angle” tethered float
switches, the kind that free-float around the sump basket, are the biggest troublemakers.
They swirl around the sump basket, making them far more likely to get trapped
against the pump, discharge pipe or power cord. Once trapped, they can't switch on the
pump. Inexpensive switches can also simply wear out or cause motor burnout.
Sizing a Pump
Whether you're buying a replacement
pump or a backup system,
you'll have to determine the pump
capacity. Here's how: Disconnect
your existing pump, pull it out of
the basket, and check the GPH
rating on the label or check the
pump's specifications on the manufacturer's
Web site. Buy a new
pump with at least that much
capacity. If your existing pump
sometimes can't keep up with the
incoming water, select a model
with a higher GPH rating.
Battery backup systems
Manufacturers of battery backup systems usually sell three models:
good, better and best, with “best” costing three times as much as “good”. The “best” units come with a larger battery and
a more sophisticated battery charger. The larger battery gives you a
longer run-time, and the better charger prolongs the life of the battery.
So how long will a battery backup system keep your basement dry?
That depends on how much water is entering your sump basket
(which determines how often the pump will run). Here's an example:
one manufacturer's system comes with a 40-amp/hour battery that's
projected to last up to 53 hours (pumping at the rate of 2,300 GPH
once every five minutes). But, if you have serious water problems such
that the pump runs once a minute, that same battery will last only 12
hours. That's hardly enough battery capacity to get you through an
extended power outage. In that case, buy a system with a larger battery,
or a system with a charger large enough to keep two batteries
If you have minor seepage and rarely experience power outages, you're
probably safe buying a less expensive battery backup system. Then
again, that savings could cost you big-time if just one 100-year
storm knocks out your power and turns a sump trickle into a flood.
Advantages of battery backup systems
- Simple installation—connect to existing discharge pipe or run a separate pipe
- Unlike water-powered systems, battery backup systems work
when there's no water supply
- Battery may run down before power comes back on
- Battery water levels must be checked every few months
- Battery terminals must be cleaned twice a year
- Battery must be replaced every five years (and costs about $100).
Figure A: Battery Backup Pump
If the primary pump fails, the battery-powered pump
takes over and ejects water. A maintainer keeps the
battery at full charge.
A water-powered backup pump uses water pressure to siphon
water out of your sump. Most use 1 gallon of city water for every 2
gallons of sump water they remove. So a pump that's capable of
removing 1,500 GPH will use 750 GPH of city water. And that's created
a lot of controversy. In fact, a few municipalities prohibit their
use due to already severe water shortages. So check with local ordinances
before buying a water-powered sump pump. In an area with
high water costs, the water bill can run as high as $170 a day. But
keep that in perspective. If your power goes out for a couple of days,
you'd happily pay a $300 water bill to avoid a flood.
Water-powered pumps require at least 40 psi and a 3/4-in. feed
line to achieve maximum pumping rates. And they require a separate
drain line and some type of backflow prevention to prevent
cross-contamination with potable water.
Water-powered pumps come in two styles: in-sump and above-sump.
An in-sump pump (one choice is the Liberty No. SJ10 SumpJet pump, available through our affiliation with Amazon.com) is always
immersed in drain water, which raises the risk that drain water could
contaminate the drinking water supply. To prevent that, most local
codes require the installation of an expensive reduced pressure
zone (RPZ) backflow prevention valve. RPZ valves must be
professionally installed and tested annually by a licensed plumber.
That adds an annual cost to the system. So check with your local
building inspection department before you buy an in-sump system.
An above-sump unit mounts well
above the sump, which reduces the
risk of drinking water contamination (one choice
is the Basepump RB750-EZ; sold at Amazon.com).
Therefore, many plumbing
inspectors require only a less expensive
atmospheric vacuum breaker
- No limit to run-time; works as long as you have water pressure
- No battery replacement costs
- No routine maintenance
- If you have a well, this setup won't work during a power outage
- More difficult installation because it requires a new water line,
backflow preventer and new drain line
- Annual fee for RPZ valve testing (if required by local code)
- May be expensive to run in areas with high water costs
Above-sump water-powered backup pump
Figure B: Above-Sump Water-Powered Pump
This pump operates like an in-sump unit, using city water to pump sump water. Both kinds of water powered systems require a separate discharge line.
In-sump water-powered pump backup
Figure C: In-Sump Water Powered Backup
When the primary pump fails, a water-powered pump uses city water pressure to siphon water out of the sump. With an in-sump version, your local inspector may require an RPZ valve to prevent contamination of drinking water.
Generator-powered sump pump
During a power outage, a generator can pay
for itself in a dozen ways. One of those
ways is powering a sump pump. A typical
sump pump draws about 9 amps, so it
won't add much load to the generator. But
a generator isn't a perfect substitute for a
backup system. A battery- or water-powered
system kicks in automatically, whether
you're home or not and no matter what the
failure. A portable generator works only if
you're around to connect it. And a generator
(standby or portable) won't help if your
primary sump pump is kaput.
Pump powered by a portable generator
Figure D: Power Pump With a Portable Generator
Run a heavy-duty
extension cord from
the sump pump to
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Know when your pump is dead
Too often, homeowners don't discover a sump
pump failure until they see the damage. But
there are ways to avoid that:
If you buy a new AC sump pump run by a
controller, it'll have some type of alarm to let
you know if the pump fails or the power goes
out. The same holds true for most new
- Local Alarm. Detects water at the top of
the sump basket using either a probe or a float
and sounds an audible alarm (such
as the BWD-HWA Basement Watchdog Water Sensor and Alarm; available through our affiliation with Amazon.com). Local
alarms are great if someone is
home at the time of the failure.
- Verbal Message Via Landline. Detects water at the
sump and dials a preprogrammed phone
number and plays a recorded message (one
choice is the Control Products WA-700 WaterAlarm Dialer; from Amazon.com). Also
sounds an audible alarm. Must have a landline.
- Text Messaging. Detects water at the
sump and sends a text to three different cell
phones. Search “high water text notification” for companies that provide this service.
How to Buy a Primary Sump Pump
Home centers sell a confusing array of sump
pumps that range from $50 to $250. But don't
despair. We've reviewed all the specs, talked
to the engineers and boiled it down to five
simple buying tips:
1. Horsepower means nothing. It's the pumping
volume in gallons per hour (GPH) that
counts. Check the capacity of your current
pump. If your current pump keeps up with the
flow during the heaviest rainstorms, buy that
capacity again. If not, buy a pump with a higher GPH rating. To find your current
pump's rating, locate its make and model number on the label and find the specs
on the manufacturer's Web site.
2. Check the “head” on the manufacturer's GPH rating. Head is the height that
water has to be lifted from the pump to the horizontal discharge pipe. More height
means harder work for the pump. The GPH rating on most good-quality pumps
includes the head (typically 10 ft.). But some manufacturers rate pump capacity
without head (“3200 GPH at 0 head” for example). That gives an unrealistic—and
misleading—estimate of pump capacity.
3. Spend the money to get a quality sump pump. Look for a caged or vertical
float switch, a motor with a UL and a CSA rating, and a pump made with a stainless
steel, cast aluminum or cast iron impeller and pump body. Avoid pumps made
from epoxy-coated parts.
4. Buy an energy-efficient pump. Once you find a pump with the correct GPH
rating, look for a model that consumes the fewest amps. This isn't about saving
electricity; high-amp pumps run hotter and burn out the float switch faster.
5. If your sump accumulates gravel or sand, buy a “top suction” pump that's “solid
passing” to prevent a stall/burnout caused by trapped gravel. Or raise a “bottom
suction”-style pump on a few bricks to keep it off the bottom of the sump.
While you're at the home center, buy a new male fitting to fit the pump outlet; pipe
primer and cement; a new check valve and rubber couplers