In order to prevent basement flooding you need to use the right size sump pump. Most sump pumps advertise horse power but this can be confusing. What you really need to know is your sump pump flow (discharge) rate to get the right pump!
Not sure what the flow rate of your sump pump. Not many people know their pumps discharge rate – or how to calculate it! Fortunately all you need to calculate flow rate is a tape measure, a timer and a bucket of water.
Keep reading to learn more about sump pump discharge rates:
How to Measure Flow Rate
Ready to get started measuring your sump pump flow rate. Most instruction manuals have flow rate tables but if you lost the papers follow these step by step instructions.
Start by determining the amount of water entering the pit every minute. Second, measure how high you need to move the water (aka the head height). Once you know all the numbers it is easy to pick the right size pump – remember higher flow rates mean more horse power.
How to Increase Sump Pump Flow Rate
Does your pump look like it is struggling to clear the water in the pit – you might need to increase the flow rate. Your pump probably advertised a maximum flow rate, but that does not mean it is currently operating at peak efficiency.
- Reduce needed lift. The higher your pump has to pump water the harder it has to work and the less water is can clear. Install drainage pipes that are closer to the water source.
- Install a filter. Some basins fill with dirt and other debris. Make sure your pump has a filter – and it get cleaned on a regular basis
- Get a larger pump. Some pumps are too small for their pit. Water table changes, new construction and additional rainfall can all cause your home (or crawl space) to need a pump with more horse power.
Flow Rate Formula
Want to calculate your pump capacity. Use this formula –
Inches of Water x 60 Minutes x 1.5 = Gallons per Hour
Pump Flow Rate Table
| Pit Diameter | Gallons of Water |
|---|---|
| 24" | 2 |
| 30" | 3 |
| 36" | 4 |
| 42" | 6 |
| 48" | 7.5 |
| 60" | 12 |
| 72" | 17.5 |
Zoeller Sump Pump Flow Rate
Zoeller makes some of our favorite pumps on the market. We did the research and put together everything you need to know about their flow and discharge rates! Use the chart below to help decide which pump is right for your home based on water flow.
| Pump | Motor | Max Head | Max Flow Rate |
|---|---|---|---|
| 50 Series | 3/10 HP | 19.25' (5.9 m) | 43 GPM (163 LPM) |
| Model 63 | 3/10 HP | 19.25' (5.9 m) | 43 GPM (163 LPM) |
| Model 72 | 3/10 HP | 18' (5.5 m) | 38 GPM (144 LPM) |
| Model 73 | 1/3 HP | 18' (5.5 m) | 38 GPM (144 LPM) |
| Model 75 | 1/2 HP | 25' (7.6 m) | 50 GPM (189 LPM) |
| Model 76 | 1/2 HP | 25' (7.6 m) | 50 GPM (189 LPM) |
| Model 95 | 1/2 HP | 26' (7.9 m) | 80 GPM (303 LPM) |
| Model 98 | 1/2 HP | 23' (7 m) | 72 GPM (273 LPM) |
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Sump Pump Sizing Calculator and Sizing Guide
How to Size a Sump Pump