Battery-backed sump pumps

[Robert Green]

Anyone have any hands on experience with battery-backed sump pumps?

Home Depot's got on for $128 that looks promising:

There are combo units:

that are an AC pump and a DC pump preconnected via wye and check-valve to a single output port. I'm worried about this design, from what I can see, because I suspect one twig wedged in the float basket will cause it to require maintenance. I am looking for as maintenance-free a solution as possible. Currently using an unknown submersible that came with the house that's failed in sump at the basement stair landing. No room for a pedestal unit. No interest in generator powered AC units.

This one (Wayne):

does 2880 gph (above pump is only 1000 gph, IIRC) and seems to rely on a single 12V pump, switching to battery when AC fails. I assume this is more prone to failure because the entire pumping load is handled by one pump, but the interconnections between the two pumps in the combo model are potential failure points as well. I suppose if I wanted a backup I could simply add an independent AC sump pump.

I'd also like to know if anyone's used the Rigid CPU-1000 - homedepot ID #

100521277 - they generate intolerably long URLs with user ID information imbedded in them - so no URL - no -wait, here's the user manual in PDF:

This unit uses a capacitance switch instead of a float to activate the pump. I assume those are more reliable than floats and that the company does as well since they offer a lifetime warranty on this model. I've had float and switch problems before in sump pumps, so I'd like to eliminate that failure vector. If the capacitance switch is just as vulnerable to a twig jam as a float switch, I'll stick with the float switch. Google groups turned up a lot of good bypass solutions for the float switch like using Waterbug sensors, etc, but if I go capacitance, I'd be far more likely to go with a built in version from the manufacturer.

Any [sane] comments appreciated!

-- Bobby G.

[ransley]

If you have city water forget the battery units and look at water powered,

and Zoeller make units. They outperform battery units in every way.

[Worn Out Retread]

That depends entirely upon where the water lines are and where the sump hole is. My house has the water at one end and the sump at the other.

[AZ Nomad]

Is power failures really such a problem? I can't see a situation where letting water run down the drain to power a waterwheel generator would be acceptable. Nor would I see the typical two hour run time of a battery backed solution as acceptable. You'd need a bank of batteries the size of a storeroom to get enough energy to keep going through a medium power failure. Or the joy of a $200 water bill.

[Pete C.]

The water powered pumps are venturi pumps. The two hour battery time is plenty since sump pumps do not run continuously. Two hours of battery time might equal 24 hours of normal sump pump duty cycle operation. For water powered, it's like 3:1 pumped:consumed ratio so in a 24 hour period you might pump out 300 gal of water and add 100 gal to your water bill.

[Robert Green]

Pete (and others - thanks!) replied:

OP here. I have a number of 12V deep discharge powerchair batteries on site, so I think I am OK for even a week long outage with heavy rain, at least if the pump has sufficient heft and the downpour is neither biblical nor tidal. As you note, it's not as if I will be pumping out the bilge of the sinking Titanic and need continuous pumping.

I've yanked the old pump and am excavating the accumulated muck to mount a new unit. The last one was not codeworthy and new wiring is needed to make it code compliant. A 12VDC unit is not subject to electrical code, something that makes it even more attractive. Waterpowered pumps add more water to a waterlogged situation so I prefer batteries and not getting waste water so close to drinking water, either. During the last hurricane several localities lost water pressure because their pumps failed. It's batteries, fer sure.

Where does one find a replacement 22 by 24" metal grate with a finer wire mesh attached that covers the sump? Was this a custom made cover or are their standard sizes and sources?

This sump serves a 25 by 50 foot basement perimeter pipe and sits outside the basement door at the foot of the concrete stairs leading from the backyard into the basement. There's room for an AC and DC pump easily. However the question of the day is what will happen if the basement floor drain backflows as it did recently? I don't believe the basement floor drain is connected to the moisture reduction system that flows to the stairway landing sump. Last week, about 6" of water entered the basement from the floor and the old pump failed, but more importantly, the stair sump is 2" higher than the floor drain and much of the basement floods before the water reaches the stairway sump.

It sounds like I need to pull the storm drain floor grate and install a check valve to prevent street overflow from entering the basement. Or else I need to dig a separate sump next to the floor drain to immediately catch any "upchucking" from the flooded streets.

-- Bobby G.

[Robert Green]

Also, the cycling of the battery operated pump gives the charger a time to top off the battery a bit before the next cycle.

That's probably a good enough reason to get them pre-strapped and preadjusted.

That's good to know. I'll bet with a small house it might even be good enough for a long while.

I can charge batteries at the neighbor's generator or in the van if it's a long outage.

Adding more water doesn't seem a good solution to flooding.

-- Bobby G.