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Water Powered Backup Sump Pumps vs. Battery Backup Sump Pumps

Jun 11, 2015 • By Matthew Stock.

Sump Pump And Battery Backup

Any homeowner who has ever experienced a wet basement knows the value of a sump pump.  The sump pump, typically connected to an interior or exterior drain tile system, takes water that would otherwise seep into the basement and pumps it outside, leaving the basement dry.

Any homeowner who has ever experienced a sump pump or power failure during a major thunderstorm will also know the value of a backup sump pump.  Battery-powered or AC/DC units will take over when a sump pump has a mechanical failure or during a power outage, continuing to move storm water out of the basement.

Lately, some homeowners have begun to consider using a water-powered backup sump pump that promises endless operation without batteries or electrical power.  Let’s compare the two and see which one might be better.

Which Backup Sump Pump is Better, Water-powered or Battery?

A battery backup sump pump is a fairly simple device – a second sump pump that removes water from a sump basin through a discharge pipe to the outdoors.  The basic variety is powered by a powerful, long-life battery that holds a charge for a long time.  When the primary sump pump fails or the power goes out, the backup sump pump kicks on and removes water from the basement.

Dual-power backup sump pumps have a battery system but are also plugged into house current.  If the primary sump pump fails without a power failure, the backup system runs off the home’s AC power.  When a power outage occurs, the backup system runs on battery power.  Dual power systems may also run alternately on a regular basis with the primary sump pump.

A water-powered sump pump uses high pressure municipal water supplied by a dedicated water line and is triggered by a second float switch in the sump basin, positioned higher than that of the primary.  When failure of the primary pump causes the backup to kick on, municipal water begins to flow through a chamber mounted above the sump pit, maybe as high as the ceiling.

Due to the “Venturi effect,” the moving water creates suction that pulls water from the sump pit and discharges it outside along with the fresh water.  When the primary pump resumes operation, the water flow stops.

The appeal of the water-powered backup sump pump lies in the fact that it will operate continuously without an external source of power.  However, it has a few glaring faults.

The typical water-powered backup sump pump measures its output based on a minimum available water pressure rating of 40 pounds per square inch (p.s.i.)   At that pressure rating, these pumps will move between 600 and 800 gallons of sump water per hour at a vertical lift of 10 feet.

Sounds like a lot but:

  • A basic battery backup sump pump will move in excess of 2000 gallons of waste water per hour at a 10-foot lift;
  • A pressure rating of 40 psi for a residence is just about the maximum available in most areas and many homes in Chicago experience as little as 25 psi.   Decreased water pressure will result in decreased pumping capacity; and,
  • The conditions in which a primary sump pump will fail are the same conditions under which a lot of water needs to be pumped out of the home to keep the basement dry.  The water-powered pump may run eternally but, if it can’t pump fast enough to stay ahead of rising water, where’s the advantage?

Here’s another, perhaps more important issue: Water-powered backup sump pumps use a considerable amount of potable water to move waste water from the sump basin — claims range from half to three-quarters of a gallon of fresh water for every gallon of waste water.  Even at the relatively anemic pump capacity of 800 gallons per hour, that’s 600 gallons of fresh water being wasted.

Water is becoming an increasingly valuable and even scarce commodity in the 21st century…just ask any Californian.  It is hard to imagine that this kind of water usage will remain feasible for very long.

Also, all that water has to go somewhere.  In many suburbs, it ends up overwhelming waste water disposal systems and, in Chicago, it is processed along with sanitary sewage at great cost.

In short, a water-powered backup sump pump may have some advantages but they are more than balanced out by their poor performance and wasteful operation.  A battery backup system makes much more sense.

At U.S. Waterproofing, we install the powerful and economical BOSS line of battery backup sump pumps and, combined with our 58 years of basement waterproofing experience, they ensure a dry basement without waste.  Why not ask for our free advice?

Want to know more about the difference between water-powered and battery backup sump pumps? Please post your questions in the Comments box below.

Tags: water-powered backup sump pump, battery backup sump pump

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