Lisab, as I understand them, water pressure back-ups don't just utilize pressure, they use lots city water to pull the sump water out by Venturi effect. This effectively mixes the clean and dirty water and leaves to copious amounts of water pouring out, which eventually goes to a storm sewer (of course, it is even worse they dump it right into a sanitary sewer). If it is a very active sump like Rusty's it would take a remarkable amount of city water to pump the sump water up 8 feet, if it could even do it. Doesn't that all that extra water contribute to straining the storm sewers, probably at the worst possible time (when it is already very wet/raining)? If many people use these and storm sewers are overwhelmed, won't flooding be that much worse? And, if enough people use them, won't the water supply be burdened? While the individual paying the water bill should care, I think the municipality should care, too. Rusty, is there any place downhill from your basement where you could drain your sump by gravity to daylight? It seems unlikely with the waterflow you describe, but, it would be the best solution by far if it were possible.

The short answer, I think, is no. Even a small sump pump pulls something like 6 amps (720 watts) so you'd need a pretty large UPS to keep on running for any period of time. From APC's runtime chart a 1500 VA back-up (retail $250) would keep 700 amps running for 5 minutes. Motors have a fairly large in-rush of current on start-up too. I don't know if a UPS is designed to handle that. The pumps sold with battery back-up systems are 12 volts DC, so you couldn't just plug one into a UPS either. It is probably far more cost effective just to buy a automated battery backup sump pump system.

The period it operates from is directly drivein by how large a battery (amp-hours) you care to purchase. It is even possible with the correct setup to parallel batteries for longer operating time. The discharge side of things is simple, the charging side for paralleled batteries is a little harder.

You shouldn't be using a trickle charger. You should be using a "battery maintainer" that senses when the battery actually needs to be charged, does the charging and then shuts off 100% once the battery is at full charge. Your batteries will hopefully have some sort of removable caps. If so, go buy a five dollar hydrometer and a thirty dollar battery load tester. These two devices are essential tools for monitoring the ability of your batteries to do their job when called on. The hydrometer will allow you to extract the same amount of battery fluid from each cell and measure the specific gravity of that mix. That measurement will tell you the state of charge in each cell. A fully charged battery will have almost the same specific gravity at the top end of the scale. If all the cells but one read as being fully charged, then that tells you that the cell is bad and the battery needs to be replaced. If all the cells show a low state of charge despite being on the charger continuously, then the battery is just worn out and must be replaced. The load tester does exactly what it says. Batteries are rated in CCA or Cold Cranking Amps. This test shows the batteries ability to put out a high amount of amps for a specified period of time. Think of it as "reserve capacity". You could put a voltmeter across a battery and it might read 12 volts; leading you to believe that it's OK. But a voltmeter won't tell you how long a battery will deliver 12 volts to a motor that draws ten amps. Amperage is the load and the load tester allows you to test for that. In other words, you could have a battery in your flashlight that will make the bulb shine brightly when it is first turned on but if that light goes out while you are trekking to the outhouse at 3.00 AM, then it has no capacity left. Of course, this is exactly what you are wanting to avoid and those two testing devices PLUS taking the time to learn how to use them properly, will put you in control of your batteries, instead of the other way around.