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Backup sump pump

Misc  ✺  Housing
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I installed a Red Lion backup 12v sump pump system, but I don't feel like the kit was well worth the money. I tried rebuilding my own kit - it's a a work in progress, I will update this page with finding later.


In the last few years, weather patterns and power grid disruptions have been increasingly erratic, and I didn't want to lose my sump pump when we lose power. Having no prior knowledge on sump pumps and available options, I've documented here my experience with choosing and installing a backup sump pump.



Our basement has a sump pit that's approximately 2 feet wide, long, and deep, located in the basement crawl space. We already have a primary 115v 1/3HP sump pump, it runs occasionally after rain and has no trouble clearing the water out.


Having experience with electronics but little to no experience with higher wattage electricity, and no preconceived solution, I started researching possible approaches.


At the time I was familiar only with electronics, and I knew little about larger wattage systems, and sump pumps as a whole. I looked around for different kits, and went with a more reputable brand (Red Lion). At the time it was about $370 at Princess Auto, not including the battery.

For the battery, the pump kit recommends a Group 27 90-100 Ah deep-cycle battery. The instruction manual says lead acid or AGM. The best deal I found was at Costco for a 100 Ah RV lead-acid battery for about $180 with a great return policy. Reddit users strongly advise against using lead-acid batteries in enclosed spaces (they release hydrogen, which is explosive), but many other sources say that it's highly unlikely. I wasn't comfortable with highly-unlikely approach, and found a 110 Ah AGM (sealed) group 31 battery at a local battery dealer (Dixon Batteries) for about twice the price.


The kit was fairly easy to install. Instructions were clear, and the most difficult part is building the Wye pipe assembly, which does not come included in the can (another $50 for the piping and check-valve). The manual instructs plugging the primary and secondary pumps on separate circuits without extensions cords, which can be a challenging ask in certain setups.


The setup works great, the 2500 GPH sump pump does a great job clearing the water when the primary pump is unplugged. I tested it with a much smaller 12v battery I had access to, and then plugged in the group 31 battery that took a few days on the trickle charger to be fully charged.

That said, the key elements of the kit are just the sump pump and switch. The sump pump seems like a generic submerged 12v sump pump. The switch is a diaphragm switch, which was problematic for my installation in two ways. The instructions say that it need 6 to 8 inches of water to be triggered, but it didn't go off until it's submerged a full 8 to 10 inches.

Given the depth of my pit, it meant that either I have to lower the trigger point for my primary point to just a very low level, or have the diaphragm switch be submerged in water. Given that the water around here is fairly hard, and the diaphragm depends on a very small hole for the water to seep in, I worry that it can easily get clogged, which means that the backup pump may not trigger at all when the primary pump fails.


The key pieces I would focus on for a backup sump pump system are the battery ($150-400, not included in kit), charger ($25-60), the pump itself ($50-90), and the switch ($0-150). Whether you buy a kit or not, you will need some plumbing connectors (e.g. Wye and back flow valves). The other elements in the kit can be purchased separately, but are not needed: case for battery ($35), buzzer alarm and LED lights.