I have an exterior sump pit which gets all the water from my downspouts and french drains and pumps it out to a rain tank and overflow into a leeching field.

Because of where the pit is, if the pump were to fail or the power went out during a big storm, the water would overflow into my downstairs.

I've seen plenty of battery back-up sump solutions online, but it's not clear to me if any of them can work in an exterior application. If I get a marine battery and put it inside the provided plastic enclosure, am I good? Is there special equipment for an exterior application?


  • How far from the house is the sump pit? Hoe cold do winters get where you live?
    – mikes
    Commented Mar 7, 2016 at 11:55
  • The unit needs to be listed for a wet location. If you use 12V the battery will be fine but the charger (120v side) needs to be protected.
    – Ed Beal
    Commented Mar 7, 2016 at 14:22
  • The pit is maybe 10 feet from the corner of the house. I live in the SF Bay Area so it's really temperate - freezing or heat are not issues. I've been looking at units with an integrate battery backup that you can get at e.g. Home Depot. Looks like I could use one, but I should put the battery unit inside the house?
    – Judd Antin
    Commented Mar 7, 2016 at 23:22

2 Answers 2


why dont you just use an UPS (uninterruptible power supply)? just locate it inside and run a cord out to your pump. that way your UPS is inside and warm and dry (keeps the electronics happy) and your pump will work one way or the other - you will also get an audible alarm if there is a problem.

  • When I ended up getting a 12V battery backup sump pump last year, a UPS that could power my 9.7A 120V sump pump long enough for it to be practical for a reasonably long power outage was impractically priced in comparison to a battery backup pump. Commented Jun 6, 2016 at 11:19
  • another thought - you can pick up standby backup generators with autostart pretty reasonalby now. this could solve the problem. just dedicate one of the generators circuit legs to the pump excusively. that should give you a days worth of peace of mind. Commented Jun 6, 2016 at 15:22

It depends if the included enclosure can fit anything else & that it's not only water-tight but also drains in case water does try to collect. Extra room is important because you'll need to either tap off of the supply wire to hook-up a trickle charger for the battery.

Also, you might need an inverter for the battery's 12volts or 24volts in order to supply & actually run the 120volt pump. Those 2 essential items might kill the outdoor backup idea altogether & it would be better instituted inside the house at the circuit panel. Which, would then require an automatic switch to pop the battery into action when the power fails.

  • Ok, thanks. It sounds like one way or the other I should put the battery inside the house.
    – Judd Antin
    Commented Mar 7, 2016 at 23:24
  • Don't get bummed out, I like the outside idea. I'm just letting you know what's involved. Outside's perfectly fine, it just needs to be right to save the house & frustration. See what an Electrician says, the whole package shouldn't cost much at all. It's no problem to tap into the pump's power for the trickle charger & the inverter's no big deal. You might just need a bigger enclosure or to bolt-on other smaller ones.
    – Iggy
    Commented Mar 8, 2016 at 0:31

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