If you already have a existing pump installed you should design your irrigation system to work with the existing pump, if possible. The Irrigation Design Tutorial will take you through the process of determining how much flow and pressure your existing pump can produce (the pump capacity), then you can design the irrigation system to match those parameters.
There is a correct way to measure the capacity of your existing pump and there are lots of wrong ways to do it. If you use one of the wrong ways, (and they are suggested all over the Internet) really bad things are potentially going to happen. One is that the irrigation system you just spent a pile of money on may not work, it may just dribble water from the sprinklers. The next is your pump may burn out. Third is your pump may surge each time it starts and eventually that will cause massive damage to the irrigation system pipes and valves. You don’t want any of these things to happen! So you need to get this measurement of your pumps capacity right because your whole design depends on it being correct. Remember, “garbage in, garbage out.”
Start by reading through the Measure Your Water Pressure – Country Bumpkin Water page of the Irrigation Design Tutorial to get an idea of what needs to be done. It will guide you through the process of evaluating your existing pump to assure it is sufficient for your proposed irrigation project.
Warning: Designing an irrigation system that uses a pump requires several steps/considerations that are not necessary if you have a city water supply. If you design the sprinkler system wrong it can wreck your pump so it is best to use a sprinkler design tutorial that is written for people using pumps! There is a lot of incorrect information online on irrigation design with pumps, including some on major irrigation company websites.
Please, read the Country Bumpkin page so you know the right way to do it! Yes, we know that’s a silly name for the page, we wanted it to grab your attention because the information is so important.
It won’t hurt to learn a bit more about pumps before you go on to the irrigation design. You might want to check out the following articles that provide background information on pumps:
After looking over those pages just hop over to the Irrigation Design Tutorial for step-by-step instructions on how to design your irrigation when using a pump.
Related how-to pump articles:
Selecting A Pump For A New Irrigation System.
How to Select a New Pump for an Existing Irrigation System.
How to Design a New Irrigation System to Use wit an Existing Pump.
How to Improve the Performance of an Existing Pump.
How to Select a Pump for a Rainbarrel.