A lot of people tell me after they find out I’m in the sump pump business… “Boy, I need a battery back up pump, my sump pump runs all the time. In fact it can barely keep up with the water coming in.”
If that is truly the case I ask them “How often do you lose power?” and “For how long?”. If their answer is that they hardly ever lose power, then I recommend just adding a secondary sump pump and setting the float switch higher than the primary pump float switch, connecting the secondary sump pump to a separate electrical circuit, and running a separate discharge line. In addition, each sump pump should have its own check valve. If running a separate discharge line is not an option and you have to “T” or “Y” them together you will only receive 75 to 80% of the combined output. I also recommend that that give the secondary sump pump some “exercise”, in other words, unplug the primary sump pump and let the secondary sump pump get some run time. Do this every 60 to 90 days for a few hours at a time. If their answer is that they lose power all the time then I confirm that yes they probably should have a battery back up pump. But I tell them to keep in mind that most battery back up pumps only put out a fraction of what a 1/3hp, 115v pump puts out in gallons per minute or hour. A battery back up pump also has limitations depending upon the age and quality of the battery.
Every back up system will need maintenance and attention, it is a commitment, and I recommend giving these sump pumps some “exercise” too. You need to make sure the sump pumps will perform when needed. I recommend you use the largest maintenance free battery that you can buy and change it at least every two years. Talk to your plumber installation technician about a yearly check up.