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Answering Your Water Pump Questions

Answering Your Water Pump Questions

with RPS Engineer Mike

How many sprinklers can a 1.5 HP pump run?

Irrigation is a complex process with lots of moving parts. To think through your system properly, you’ll need to have a reliable source of water, as well as a clear understanding of the volumes you’d be wanting over a 24 hour period. For 1.5 HP pumps, we can run through some specifics that might be helpful for determining a range of sprinklers they would work with.

Image 1: 60/80-RPS Series Pumps

Take our 60RPS15 for example (the yellow line). This is our highest GPM 1.5 HP pump, with about 90 GPM at 0’ of lift and about 55 GPM at 75’ of lift. This is a great pump, the issue is that it might not be a great choice depending on the sprinkler head. Are you looking to run Big Gun 60 PSI sprinklers for large-scale irrigation? If so then the pump won’t be able to build the appropriate amount of pressure (since 60 PSI is equivalent to about 140’ of lift). If on the other hand you’re hoping to run smaller household sprinklers at about 25-30 PSI, that may work well for you. 25 PSI is equivalent to about 60’ of lift, and the pump would do about 60 GPM at that rate assuming no other lift. At 5 GPM per household sprinkler, that’s 12 sprinklers at a time. Even with a higher GPM of 10, which some household sprinklers run at, that’s six sprinklers that can run at a time. That’s not even accounting for the fact that running sprinklers in zones is common practice, so over 24 hours at 1 hour per zone you could be looking at theoretically more than 125 sprinklers at 10 GPM. A bit of overkill for a standard suburban house, but for some of our rural customers that could be a necessity for their landscaping.

Figure 2: 25-RPS Series

 

For higher PSI applications, our 25RPS15 is often a solid choice. At 60 PSI it’s pumping at 28 GPM assuming no other lift. That’s enough pressure and GPM to run a smaller Big Gun Sprinkler, which for a 1.5 HP pump is quite impressive. If you have a set of irrigation sprinklers in zones running one at a time this pump would be able to handle all your irrigation needs.

We have a wide variety of 1.5 HP pumps; these two options are common for irrigation but you may want to look through all our pump curves and see what’s applicable for you. I’ve been assuming there is no lift in these examples, but that’s not normally the case, so a smaller volume high head pump may be necessary for deep wells. Another question to ask yourself: Are you running anything besides sprinklers? If you only have one well running your entire household you may notice a drop in pressure or volume in your house when you’re running sprinklers. That’s why on occasion I’ll suggest pumping to both a storage tank for your irrigation and a pressure tank for your household. Both tanks would have pressure shutoffs (a mechanical float for the storage tank) and trip the same pressure switch; the pump would be wired to only shut off when both tanks are full. Then from the storage tank you could run an EcoSteady Booster Pump that pumps out a set PSI at constant pressure for your irrigation. In this way you’re splitting the load of irrigation between two pumps, and ensuring that your household also has constant pressurized water. This application is really only relevant for folks with larger gardens or landscapes that are looking to use at least a couple hundred gallons per watering session, but it’s a fun idea!

The great thing about pump sizing is there’s always some different numbers floating around, that’s what we specialists are for. If you’re interested in chatting through your irrigation needs, we’ve got that covered as well; just call in and ask for someone who likes talking about gardening and we’ll patch you through! You can call us at (855)-560-5670 or email us at help@ruralpowersystems.com. Let’s figure out how to get a pump and accessories tailored just for you!

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