Sprinkler System Water Pressure - Too Much of a Good Thing

I'm not talking about the pressure of meeting a deadline or taking the last second shot. I'm talking about serious pressure. Measurable, pounds per square inch pressure ... water pressure. Anyone with a nodding acquaintance with irrigation knows that sprinkler systems rely on sufficient water pressure for the heads to pop up and water properly. But what if there's too much of a good thing?

We're Talking PSI

The optimum operating pressure for most residential sprinkler heads is between 30 and 50 pounds per square inch (PSI). With correct water pressure, each head will perform the way they were designed, and the result will be even spray-patterns and efficient use of water. The problem is that the operating pressure of most sprinkler systems is dictated by whatever water pressure exists at the main supply line. This is often well in excess of what the system can handle, sometimes reaching over 100 PSI. Too much water pressure left unattended will result in wasted water and potential damage to the sprinkler pipe, heads, and valves.

Lower PSI, Lower GPM Equals Less Waste and Lower Water Bills

Water will be wasted in two major ways. First, small droplet size produced by high pressure will cause water to drift off-target. In severe cases, it almost looks like fog and you can hear it spitting out of each head. Second, water will come out unevenly and too fast. Individual heads can use as much as three times their designated gallons per minute (GPM). Too many PSI = too many GPM. All this extra water can't be distributed evenly so some areas get way more than they need.

Detailing all the possible damage to your system from high pressure is more complicated (spelled b-o-r-i-n-g). If you're comfortable just knowing it's bad then skip the next paragraph, if not ... read on McDuff!

Size and Quality Matters

Residential sprinkler systems typically use either 1" or 3/4" diameter pipe (or some combination of the two). Each size pipe has restrictions on how much water can safely run through it without causing problems. These are based on the type of pipe (PVC or Poly), the inside diameter and the thickness of the pipe walls (called the schedule, i.e. Schedule 80 pipe). Under high-pressure conditions, more water is forced through each head than designed which increases the total volume of water used in each zone. To accommodate this increased demand, the water traveling through the pipe speeds up. This combo of high pressure and velocity, along with stress they create, will cause inferior pipes and components to fail and decrease the life of even the highest quality materials.

What to do? There are a variety of possible solutions, but here are but a few: choose the correct size and type of pipe, have the correct number of heads with proper nozzles for each zone and install pressure regulation on the main line, valves and/or heads. Depending on the severity of the problem, you may need to use more than one solution.

If you suffer from too much day-to-day stress, self-help books or a cold compress might prove to be your solution. On the other hand, if it’s your sprinkler that’s under too much pressure, proceed directly to a licensed irrigation professional.