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Question DetailsAsked on 6/17/2015

Is a water powered sump pump backup a good idea?

I am trying to insure that my basement does not flood in case we lose power. I want to know if I should get a water powered sump or a battery powered backup or a generator.

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1 Answer


Good and bad features with each.

- Battery backup requires battery replacement every few years, and needs an automatic charging system and low-battery and power-loss alarm to be useful, and needs to have a good surge protection system on it so it does not fail from a lightning hit on the power lines. Also, unless it is powering a totally independent backup sump pump, the battery-to-120V backup systems are no use if the sump pump is what failed, not just the electric power. Tends to be an install-and-forget system, meaning they commonly are not operational when needed - hence the need for low battery and high water and power-loss alarms. Also - operational life is short - typically a few hours only unless you install massive batteries, so unless you configure secondary wiring so you can recharge the battery by jumping from a car, will not be a secure backup in a prolonged power outage. Nor is it secure if your house loses power while you are gone for an extended period of time - during early hours of a workday, away for weekend or on vacation, etc. Moderate cost.

- Generator backup assumes the generator will start when you need it to (Murphy and his laws get involved here commonly), that you will have enough fuel to run it as long as needed, that generator/fuel will not be stolen if a prolonged power outage, and unless a larger one with auto-start system (which commonly fail to do so when needed) means you have to be home to start it - so that degrades the reliability dramatically. If pipeline-supplied natural gas powered, that also degrades the reliability in major disasters that could take out the gas company compressor stations for an extended period of time. Highest cost.

- Water powered system is automatic and genearally totally non-electric (though should still have sump pump power loss alarm so you can check backup is working, and high-water alarm in case it fails), so unless the pressure valve or high water float in the system fails should operate whether or not you are there at the time, and does not run out of power, so probably the most reliable in the long run, assuming you do not get a Chinese cheepo version. Also pretty easily put into a sump alongside the normal sump pump, whereas putting a battery-operated normal sump pump into the same sump with your normal pump can be a problem at times. Downsides - in major emergencies (especially major earthquake, major flood, major fires, major hurricane) water pressure in the public system may fail or drop so low it does not work right. Also, I have seen one house with this system where it turned on in a power outage, but the checkvalve stuck open so instead of pumping out the water in the sump, it dumped several thousand gallons into the sump - rare, but can happen if pump is not designed right so the venturi cannot backflow. Requires decent household pressure (typically around 40 psi) to work well so not viable in really low-pressure areas, and of course useless if you are on a well system powered by public power - which could be your own private well, or a local cooperative or private water system which might not have automatic backup generators. Obviously, in a major earthquake where pipes break a lot its reliability is low, though of course that is a very rare event, and if that large a quake you likely will have bigger problems than a flooded basement to worry about. Larger public "city" water is usually pretty reliable in power outages unless the emergency is such that it cuts out the emergency power to them or drowns them out. This type sump pump is also illegal in some areas because it uses a fair amount of water which might be needed in an emergency situation - I know some areas in California outlaw them for that reason - to conserve water usage if power goes out in major quake or brush fires. Also illegal in some water-restriction areas - commonly illegal as primary sump pump system at least in most areas due to water wastage issue, so check with local building department. Probably lowest cost, or maybe comparable to battery backup depending on how far plumbing has to run to get to it, though could use flex tubing for that.

Answered 4 years ago by LCD

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