The first step is to determine what size water powered pump your house's plumbing system will allow. Use the 5 gallon bucket test to figure this out. You want to make sure that the water flow rate in your home is sufficient to support the operation of the water powered pump you choose. Once you establish that, you can always decide to use a pump with a smaller capacity than your home’s water supply will allow, but you must not use a larger one.
Keep in mind: when you buy a water powered pump, you may not necessarily be able to match the capacity of your primary sump pump. As mentioned above, your choice of water powered pump may be dictated to you by your home’s water flow rate. Also, even though your home's primary sump pump might pump at 3,000 GPH (gallons per hour), for example, it may not need to run very long during each cycle to drain your sump. A water powered pump, on the other hand, is designed to sit unused for long stretches of time, and then jump into action when needed, powered by the alternate energy source of your home's water pressure. It is not intended to serve as your primary sump pump. As such, it might take longer to empty your sump pit on each cycle than your main pump does.
Follow the steps in our article on estimating sump pump capacity to determine how much capacity you need. Keep in mind that your home's water supply flow rate might constrain the water powered pump capacity that you are able to install, which might mean that you have to settle for a narrower "safety factor" (a term mentioned in our article) than you normally would prefer.
Once you get a sense for how much capacity your plumbing system will allow, along with your sump pit's volume needs, determine the "head" (also known as "lift") that your discharge piping system imposes on your sump pump (see our article: sump pump head). The greater this lift distance, the more work your pump has to do to pull or push the water out of your house. By determining the specific amount of head for your discharge piping setup, you can then get a sense for the backup pump’s effective volume, once it is installed in your basement.
Finally, armed with the knowledge of your home's plumbing system capabilities and your capacity needs, use the Product Chart and Water Supply Checklist on our water powered sump pump category page to select the right Basepump water powered pump for your home.
This article is intended for informational purposes. Before beginning any construction project at your home, please ensure that you take necessary safety precautions and consult construction professionals whenever necessary.