Correct sizing of irrigation boost pump from city supply

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cartim

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I am currently designing the landscape and irrigation for the almost 1 acre property we own. From the water meters to the highest part of the lawn about 400 feet away in the back yard is only about 18 inches height.

First to explain this setup. When we moved in, the existing, and very poorly designed irrigation did not work at all and was lacking any pressure. Since we don't want too many valves to water this large yard using the existing low pressure, I paid the city to install a larger 1" meter to replace the 5/8" meter we have. Problem was, they told me before installing, is that the supply from the main is shared with the neighbor on an approx. 125 foot long 1" cpvc line to this meter tapped from the 4" city main, so they could not install a larger 1" meter where the existing meter was because they said there would not be enough for us and the neighbor with that scenario. So what they did is made another tap into the city main down the road. Ran a 1" dedicated flexible pvc or pex line from the main and installed a second 1" sized meter on the other side of our lot. This 1" line being about 75 feet from the 4" city mainline tap. So now we have a 5/8" meter on one side that feeds the house and the 1" meter on the other side that will be dedicated irrigation. So two separate meters. There is zero elevation difference between the main and the meters.

The 5/8" meter supplying the house, measured at the house hose spigot with the highest pressure, with the regulator turned on full, is 60 psi static, and about 10 psi dynamic, flowing at only 8 GPM. The supply line to the house from the 5/8" meter is 1" cpvc then reduces to 3/4" cpvc before entering the slab. I had capped the 1" outlet near the meter for the old sprinkler system.

The new 1" meter pressure and flow, measured at the outlet side of the meter, is also 60 psi static, 25 psi dynamic, and flowing at 11.5 GMP. And as mentioned this is tapped from the 4" city main approx. 75 ft away and ran through a 1" flexible pvc line, either pex or hdpe.

I planned to design the furthest group of turf sprinklers to run on 25 to 30 GPM, so that I could have many less stations for turf along with the several drip irrigation valves that require much less pressure and flow. But with what I have available from both meters will require a boost pump to pull more out of the city main to supply that much flow.

Taking into consideration the available pressure at both meters. I plan on running a 1" pvc line from the 5/8" meter, and a 1.5" line from the new 1" meter to merge at a boost pump to hopefully pull the planned 25 to 30 GPM out of the city main, while leaving enough GPM for both the neighbor and our own house supply. The question. Can I pull that much from the city main (velocity) through both the 1" and 1.5" pvc lines, and through the city supply lines noted about before the meter, with the pump, and still have enough for the house when the turf irrigation zones are running? There are no city limitations here but only the courtesy to the one neighbor while leaving enough available flow for our house as well, even though I will be running the irrigation very early in the AM. So available gpm to our house is less of a concern.

More questions, if this pump scenario will work, does the discharge mainline to the furthest valves need to be 2" minimum? And also any good recommendations for what pump to use for what I am trying to do here? Along with any accessories such as a pressure switch to cut off the pump for the lower pressure (25 psi) drip system, and a pump relay to connect to the irrigation controller. I am looking for a very reliable, complete setup for what is necessary without going super expensive.

Thanks for your time in reading and if I left out any required info after all of this let me know.
 

Valveman

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I would think if you go with bigger lines from the meters, the meters will be the only restriction. The city main pressure should not be effected much no matter how much you draw. Only others on the same meter would be affected. You may not be able to get 30 GPM though one 5/8 meter without loosing a lot of pressure. Check the flow rate for the meter.

However much you can draw without pulling the pressure on the meter to zero, will be all you can get. Figure maybe only 10 PSI feeding the boost pump, so you need a boost pump that can do 25 GPM at 50-60 PSI. The boost pump also needs to have a max pressure of about 80 PSI to work with a 50/70 switch. A Goulds J15S pump and a PK1A control kit would do it. Just set the pump system to work at 50/70 with a Cycle stop Valve giving 60 PSI constant and you can run large zones or small without cycling the pump to death. Put a little pressure reducing valve on the line going to the drip so the drip only get the 15-25 PSI it needs.

Shallow Well Pump with PK1A.png
 
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