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Answering Your Water Pump Questions

Answering Your Water Pump Questions

with RPS Engineer Mike
Water pump for house well system

What size water pump for a 2 story house?

This is a great question! You’ll need a bit more pressure from whatever water system you have to reach the upper floor faucets and bathrooms. Properly setting the PSI of your pressure tank is key here, you’ll want at least a 50 PSI or 60 PSI setting to ensure that the water pressure on the second floor is the same as the first floor. Once a water pump pushes water into a pressure tank, the well pumps job is over and the pressure tank is responsible for delivering pressurized water to faucets within the home. 

You’ll need to size a water pump that can handle pumping into a pressure tank set to at least 50-60PSI. Sizing a water pump for any home primarily depends on the depth of your well and how much water you need to pump during high demand (plus a couple more factors). Read up on our blog about sizing a water pump here.  

Sizing Well Pump by Water Usage

Lets talk about sizing a submersible well pump based on how much water you need to pump during high demand. Our engineers always recommend that if possible, size a pump for the “worst case scenario”, in other words if two people are taking a shower, some is running the washing machine and a faucet is turned on all at the same time, how much water would the require? The more people and appliances you have in the home, the higher the worst case flow that you should expect to calculate for. 


Here’s an example of some estimates of flow rates in gallons per minute of appliances…


Washing machine 3-5 GPM 

Dishwasher 2-4 GPM

Kitchen Faucet 2-3 GPM

Shower 1-3 GPM 

Toilet 2-3 GPM 

Single Lawn Sprinkler Head 3-5 GPM  


Using the previous example as a model calculation with the upper range…


Shower #1 3 GPM + Shower #2 3 GPM + Washing Machine 5 GPM + Faucet 3 GPM 


= 14 GPM total 


As long as your well has a production rate of at least 14GPM, you should choose a water pump that can pump 14GPM.  If your well has low production, our engineers recommend purchasing a larger pressure tank, at least 100 gallons, to provide a buffer between the pump production and the home consumption.

Previous article What to Look for When Buying a Water Pump
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Learn More About Water Pumps

  • Well pump flow rate

    How many GPM is a good well pump?

    Water needs can differ significantly depending on circumstances, and you may need a submersible well pump with a significantly higher or lower flow rate, depending on household size, irrigation needs, and sprinkler use.
    Read now
  • Submersible Well Pump and Pressure Tank

    Can you put in too big of a pressure tank?

    When it comes to sizing a well pressure tank, there really isn’t an upper limit as to how big of a tank you can put in. There are some pros and cons to different size pressure tanks, and they can have an impact on the lifespan of your pump.
    Read now