One zone of my sprinkler system comes on at times and not at other times. We have 70 PSI at the meter coming to the house which drops to 20 PSI when the zone comes on. If the heads come up, the pressure rises quickly to 35-40 PSI. If the heasd just gurgle and squirt, then the pressure remains at 20 PSI. We have had the backflow checked as well as the water meter replaced. I don't know where to turn as they come on sometimes and not others. Any ideas what would be causing this?
Sprinkler pressure issues
sprinkler-system
Related Solutions
is something I can do?
This is absolutely something that you can do!
You will want to find he first / main valve box. It's usually the largest one and often rectangular. It's usually adjacent to your house, or to your water meter.
Open the cover, and identify all blowout valves. They are often quarter-turn ball valves. There are four brass blow out valves in this example with little black caps on their connections to keep dirt and bugs out:
Check that each of the blow out valves are solidly closed. It not, close it. You may need a straight blade screw driver.
Then, open the larger flow shut-off valves of which there are two in the picture above. The handle should be parallel with the pipe when it's open for every such valve I've come across. You should hear a brief 'whoosh' of water when you do this, and if you'll stay dry if all of your blow out valves are closed.
Then go to the controller and run each zone one at a time and look at the heads to confirm they're working properly. Adjust the heads if you want (though you could do that any time of year). If any are broken, flag them and call your sprinkler guy to fix (or head to his supply warehouse and buy the parts to do so yourself).
Charging someone to 'turn on' their sprinkler system in the spring is the biggest scam in the book. In my part of the country there's no annual requirement to check backflow on residential, and sprinkler companies don't anyway. I've helped out neighbors by turning their on, and It doesn't take me 3 minutes, in the dark.
Charging someone to 'turn off' their system is likewise also a huge rip-off, unless they're also going to thoroughly blow the system out to prevent freezing damage in applicable climates. Even then if you don't watch them do it they can easily do a partial job to save time, so I have never paid someone to blow my system out.
Biggest advantage to paying for sprinkler 'winterization' I can think of is there's an implied responsibility if they do it wrong and your system is damaged, but good luck proving it if they want to argue about it.
Also you need a very good (high flow rate) compressor to blow your system out, or to rent one made for that purpose.
Water pressure drops come from two sources:
1) A constriction in the line upstream, limiting the maximum inflow you can get.
2) More demand on the line, producing more outflow than the inflow can fully pressurize.
If a sprinkler zone is larger (serves too many heads), or if more zones are active at once, it will demand more water. Dividing the zone could be one solution.
If a sprinkler zone's pipe is kinked or otherwise obstructed, it may not be able to deliver as much water as is needed to fully pressurize the line.
If running the sprinklers reduces pressure at the sink, the point limiting that is going to be upstream of both, and you're probably also seeing pressure drops at the sink when you flush a toilet or run a bath. You can check for restrictions working back toward the source (valves not fully open, for example), but if the shared flow limit is what's coming into the foundation...
Best Answer
Reason
A sprinkler head's pop-up mechanism seals and becomes water tight when fully raised/extended. This only happens after being supplied with sufficient water.
A sprinkler that is not fully extended will allow more water to exit than the same sprinkler that is fully extended. The high water pressure actually creates its own water tight seal, and only allows water to escape through the spray head. Low pressure water will escape from around the pop-up mechanism and the spray head.
The catch-22 is that with too low of pressure, the system can't self seal and build up pressure. It will do what you're seeing and just continue to never seal.
A way to test that I'm correct is to get a small group of people and have one person stand over each sprinkler head and pull it up while the system is showing these symptoms. Fully extending all of the sprinklers manually and holding them there will seal the system and make it start working on it's own. They could all now walk away and the system will continue to work until it is shut off.
After my explanation, it may seem like I'm saying that your problem is low pressure. Your problem is actually low flow. Water pressure only exists because of a restriction to flow. If you cut off the end of your water main after your water meter and let the water freely shoot towards the sky, you'd have 10 gallons per minute of water going everywhere, but your water pressure would actually be at 0 psi. Water pressure doesn't mean much without knowing the amount of flow as well.
It's confusing because your sprinklers seal from both flow and pressure in a way. They seal when the restriction to flow is great enough to raise the heads and make them stay there. If you don't have enough flow, you'll never build up enough pressure to overcome the leaks around the pop-up mechanism for it to self seal.
If we can increase the flow at startup to this zone, it will make the sprinklers seal. Or if we can decrease the number of sprinkler heads on this zone, we can reduce the flow required to make the the sprinklers seal.
Solution
The solution requires you to find out why this one zone is different from the others. Does this zone have more sprinkler heads than the others? Reduce the number of sprinklers on that zone.
Is this zone at the end of a long run of a copper pipe that's too small of diameter, or a galvanized steel pipe that's corroded and restricts flow inside? Install a larger diameter pipe from your main to your valve.
Is your sprinkler solenoid valve only 3/4"? Increasing it to 1" might be all you need to do. The sprinkler solenoid valve is typically the largest bottleneck in the entire system.
Splitting your misbehaving zone into two zones is an option, as that will cut the flow required to self seal in half.
If you can't do anything significant like that, your final option is to replace your sprinklers with low flow sprinklers with the same coverage. You'll need to water for a longer duration, but it'll reduce the flow required to self seal the system at startup.
Conclusion
Anything that will increase flow to this zone and removes bottlenecks, or that reduces the amount of sprinkler heads or the sprinkler head flow will be how you fix this problem.