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Where does your irrigation system connect to? Is it a exterior house hose faucet or a direct tee connection to your mainline that feeds the house from the street. One will be street pressure (higher) and one will be house pressure (lower). Let us know that first and then we can go from there. Aloha

Thank you very much, Lehua! I'm not sure where the water's from. From the outside, I see some pipes coming out of the ground. I attached two pictures. I think the ones with valves are for the sprinkler, but not sure.

here's another picture of the left part of the first picture

For most systems, capping off some sprinkler heads will make the operating water pressure higher.

The right way to build a system is with a pressure regulator before the valves, but that can add almost $100 of cost so most people skip it.

Without the regulator, pressure will depend on the flow. Most water mains exceed the recommended water pressure for sprinklers. Mine comes in at about 110 PSI. Sprinklers like to run around 40 or 25 PSI.

The reason it usually works is there are so many heads on a zone that the valve restricts the flow and brings the pressure down. When you cap off some heads, the pressure goes up.

Many valves have a flow control option and if yours does, you can adjust it to bring the pressure back down to the optimal level. If your valve does not have flow control, you can implement your own with a gate valve in series with your sprinkler valve.