Evaporation can cause an irrigation system to waste a significant amount of water.

In Part 2 of our Drought Solutions video series, Bob Franchetto, DBDS Maintenance & Construction, shows you how to quickly minimize evaporation through pressure regulation.


Pressure Regulators That Minimize Water Loss - Video Transcript

Minimize evaporation. How many times do we see this every day? Or better than that, how many times do we see this? We see this every day for sure.

What is your standard operating pressure here in San Diego? What's your static pressure? Ok, so you're 50 or 60? 50 or 60 static pressure?

Yesterday static pressure was 80 sitting at the store and working pressure was about 65. 65 psi on a gear drive rotor is too much. They're 40 to 55, 40 to 60. You know, too much and you get a lot of evaporation.

What's the standard operating pressure for a standard spray nozzle? Little low.

30. 30 psi. So on the same system when we got sprays, at 65 coming in, you're gonna have a ton of the atomization of the water and that's evaporation.

There goes your 20% savings. Let alone this property manager is not real happy with as much moisture as he's got on all of his sidewalks and his building.

rotor evaporating

What to Do When You Have Too Much Pressure

These are opportunities. If we're going to fix this, how would we fix that? This is a gear drive rotor. How would we fix that pressure?

Pressure regulator. So everybody knows we could put a brass pressure regulator on the whole system and knock that pressure down.

So, if we we're gonna change just this one valve that's running right here. How would we change of pressure on just that one valve?

Does everybody know what a PRS dial is? Every manufacturer makes one. This happens to be Rain Bird's. It's a PRS dial.

You take the standard solenoid off your valve. Pull it out. Install this piece. Put your solenoid back on top. So now you've got this assembly that's like that on top of your solenoid. Screw this device in and this is your dial regulator, and I'll send it around.

And now you can dial in whatever pressure you want that system to work at. Not a shovel one came out of the ground.

It's called a PRS dial. A pressure regulating stem, because that's Rain Bird's pressure regulation.

How to Check Pressure

It's got a little Schrader valve on the back side. So you can check to see that that pressure that it actually is reading on that dial is what you're getting.

Better than that, take your pitot tube and go out to this nozzle right here and check what the pressure is. Cause that's where we want the pressure to be. So we may be at 50 psi here at the valve, but now we're at 45 at the nozzle and that's perfect.

And that's what we want. That's how we get the most efficient system. Water going out in proper droplet size and not evaporating. That's how we do it.

This is the little dial device. You can see, mess with the dial, it moves. Real, real simple way, without digging, to change pressure.

Changing Pressure in an Irrigation System

Can you change pressure any other way on a system? How do you make pressure go up on a system? There's only one way. Simple. A pump. You can only make pressure go up with a pump.

There's only one way to make pressure go down. Pressure regulator.

So now I'm gonna get the question of, "Oh no. You can make pressure go down! All you gotta do is cut down on the flow control."

We've got smart guys in here. Cause that always comes up. Every time.

That doesn't change pressure. That changes velocity. How fast the water is going through the valve. That's all that does. Velocity changes will look like pressure reduction, but that's not what it is. Cause your pressure is still the same on the incoming and the outgoing unless you have a PRS dial or some sort of regulator on it.

When you change velocity, that's fine tuning that valve. And is everybody fine tuned every valve out there in the system? Sure we have!

How to Fine Tune a Valve

Does everybody know how to fine tune a valve?

Let's say we're fine tuning this one right here. Simple. No matter what valve it is. If it has a flow control, get in that valve box when the system is running and you crank this flow control down until you see that system start to fail.

As soon as you see it start to fail, back it off about 1 1/2 turns and let it sit.

Your valves will now close at a more even rate. They'll close quicker and there's almost no way for this valve to stick on now.

The majority of the time when a valve sticks on, it's because the diaphragm gets shoved up into the top of that bonnet cavity so far that it creates a small vacuum up there and that assist spring that's in there isn't strong enough to break that vacuum. And the valve sticks on. Controller can be completely turned off, but your valves sticks on.

You fine tune, you tune your valves. Now you're keeping more water on top of the diaphragm. It aids in the closing.

4 Types of Pressure Regulators

Pressure, we just went through all the pressures.
1. Pressures may be reduced with a pressure regulator for the entire system.
2. Pressure may be reduced at the valve using a PRS dial.
3. Pressure may be reduced using a PRS spray body. That's a huge one. We're going to talk more about that.
4. Pressure may be reduced using a pressure regulator built into the control valve.

And minor pressure reductions may be made using the valve's flow control. True or false? False statement. There's a lot of folks that think that's true.

"Oh, I change the pressure. I cranked down on the flow control."

No, you didn't. That pressure is still 45, 55, 65, 75 going through that.

Every valve should be fine tuned. 99% of the valve boxes I go out and jump into, that valve is all the way open and somebody is complaining cause they're having a problem with it.

Turn on the system. Fine tune it down. Start there. Get it to where it works and say ok, let's operate a cycle and let's see what it does.

Traditionally your problems go away and it's usually because you got a stuck on valve and it created vacuum up in the top of that. Traditionally that's the issue.


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