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How Deep Are Sprinkler Lines? (And Can You Plant Over Them?)

How Deep Are Sprinkler Lines? (And Can You Plant Over Them?)

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Having a sprinkler system in your yard can be an easy and efficient way to keep your plants watered on a regular basis. There are above ground sprinkler systems, but they can be a pain in the rear to deal with primarily when it comes time to mow the lawn.

Planning out the layout of your irrigation system is the first step. When you are confident that the plan will work properly, you can start moving toward the installation. This is where you dig out your trenches and then eventually lay the pipe.

But digging the trench to the proper depth is important. When the trenches aren’t to the requisite depth, it is possible that some routine lawn care could wind up piercing your sprinkler lines.

This will require you to dig up your pipes, replace them, and then dig your trenches deeper.

Before Digging and Some Depth Requirements

No matter how good the plans are, they can go bad in a heartbeat without some preparation. Before you start digging, make sure that you call the local utility companies so that they can come and mark any buried lines; these are your water and gas lines.

It is also a good idea to call your municipality’s building codes department. This can be for either the city that you live in or the county itself.

Each area has different requirements when it comes to laying irrigation pipes that will determine how deep that they have to go.

Generally speaking, most areas will require that you bury your pipes anywhere from 8 to 12 inches below the soil’s surface. This measurement starts at the top of the piping and reaches to the soil’s surface, so the trenches have to be slightly deeper to accommodate this.

So, if you’re using a pipe that has a diameter of two inches and you want to bury it 10 inches underneath the soil, the trench that you dig has to be 12 inches in depth.

The reason that you want to bury them so deep is two-fold. The first is to protect against potential damage from lawn care equipment. Your standard mowers and trimmers aren’t anything to worry about, it is the aeration tools that you have to be aware of.

The real reason for burying sprinkler pipes at that depth is to protect the pipes from freezing. If you live in a warm climate, this isn’t a problem, but in areas where the winters are cold, that depth can provide proper freezing protection.

When cold snaps blow through, the cold generally doesn’t go down that deep, protecting your sprinkler lines.

Digging Your Trenches

Before you start digging, there are a few things to consider. You could do the entire thing by hand using a shovel but that can take a lot of time and even more energy.

While budgets are understandable and important, it may be worth saving the effort by going with a different process.

If you must dig, you can help yourself out by watering the area for an hour at least two days before you plan on digging up the site. This will allow the water to soak deep down into the soil, softening it up for easier shoveling.

For the larger yards out there, you should probably rent a trencher instead of trying to do the entire thing by hand. A trencher can save you a lot of time and even more stress on your body.

Best of all, they can be rented at a local garden or home improvement store relatively inexpensively.

Whatever route that you choose, digging the proper depth is imperative. Anything less and you run the risk of doing damage to them during lawncare or allowing them to freeze during the colder months of the year.

The best way to provide water for your sprinkler system is to connect it to your water line’s existing spigot. If you want to do it in the most traditional, professional way, you could tap into the service line of your main water line.

Whichever way you choose, it will require installing an anti-siphon valve. That valve is meant to prevent lawn chemicals, brackish water, and fertilizers from getting into your main water supply.

When digging the trench, start by making it around 8” to 10” deep and have the sides slope down at a 45-degree angle. When you dig, make sure that you keep your sod on one side and any soil on the other to make the process of filling in the trench as easy as possible.

The reason that you won’t dig the entire depth of the trench with your trencher is that the last couple of inches will need to cover the valve manifold box. Put it in the ground and make sure that you dig a hole that is only slightly larger than the manifest.

When you’ve laid the manifold box into the ground, take one end and attach it to the main water line, tightening the clamps to properly secure it into place. From there, you will need to connect your PVC piping to the open portion of the valve manifold.

Keep laying your piping along the open trench and use T connectors for any pipes that run directly off of the main line. You will want to attach risers at certain points, using 90-degree connectors at each of the intersections.

Also, when you glue these sections, make sure that you use a thin layer of adhesive and apply it smoothly.

With the sprinkler lines in place, you can now begin installing the sprinkler heads. Make sure that you choose ones that will fit best with your landscape as well as the irrigation needs that your lawn has.

It isn’t simply plug and play; you can get the choice wrong if you don’t do your homework.

Before you attach the sprinkler heads, you will need to flush your system completely using water to push any debris out of the system. When you’re satisfied that the line is clean and clear, install your sprinkler heads onto each of the risers of your irrigation system.

Make sure that you make the sprinkler heads level with the soil level and then fill your trenches back in with your sod and dirt piles.

Finally, install the controller. This controls both the frequency and the length of waterings that your irrigation system implements. Just make sure that you follow manufacturer specifications when installing the wires and then connect to the main water line to see if the system is working.

When you’re comfortable that everything is properly in place, you can then tweak your sprinkler heads to get the optimal coverage of your entire yard.

Can You Plant Over Sprinkler Lines?

Because of the aforementioned 12” depth of the sprinkler lines, the question becomes whether you can plant anything over them. Generally speaking, it is a good idea to keep anything that you plant at least 15 feet away from your pipes.

They can be a little bit closer if you go with something that has a deep root system. They will generally bypass the irrigation to find deeper, more lush soil. It is the trees and plants that have shallow root systems that can be the problem.

Shallow root trees can become intertwined with the sprinkler lines, restricting them or even puncturing them. When the sprinkler lines are damaged, you will have to dig them up to repair or replace them. This means a lot of time (and money) spent fixing a problem that could have been avoided.

If you can help it, plant anything at least 15 feet away for peace of mind. But if your space can’t accommodate that distance, go with plants that have a deeper root system to avoid damaging the sprinkler lines.

How Many Sprinkler Heads Can Be Used Per Valve or Zone?

Your irrigation system will only have designation to handle a certain amount of sprinkler heads per zone or valve. If you overload that particular valve, it can bring down the pressure of all the related sprinkler heads in the area or it may prevent them from working completely.

To know how many sprinkler heads you can use per zone, you have to first know your flow rate and water pressure. It is also a good idea to get uniform sprinkler heads.

Each head has its own different water pressure and, thus, consumes water at a different rate. If you have many different sprinkler heads, you will need to know the difference between them.

To check your water pressure, you will need a pressure gauge. Screw it into the faucet that is closest to your water meter and make sure that there isn’t water running anywhere, both inside and outside.

When you’re certain there are no other areas using water, turn on the faucet that has the gauge attached.

The gauge is there to show you what the water pressure is. It is measured in pounds per square inch (PSI). If you don’t have a pressure gauge or don’t want to go and buy one, you can also call your local water company. They should be able to tell you what the water pressure is.

For measuring the flow capacity of your home, you will need a measurable container. You can use something such as a five-gallon bucket if you have one laying around. Like you would with the water pressure, turn off every other faucet on your property.

Turn on the faucet where you have your bucket all the way and keep track of how long it takes to fill the entire container.

So, if it takes 300 seconds to fill a five-gallon container, you would divide that 300 by five to come to the conclusion that it takes 60 seconds to fill a gallon container. That is your water capacity or flow.

A good rule of thumb is that you should have between four and six sprinkler heads for every zone in your irrigation system. Having more than that would make your water pressure in that zone go down and thus reduce the water pressure of each of the sprinkler heads.

Fixing Low Water Pressure

If you have the appropriate amount of heads per zone and you are still getting low pressure, the first step is to shut the water off at the source so that you can troubleshoot the issue. The heads are going to be the first point of investigation.

Start by digging around the sprinkler head in question and unscrew it from the riser. You can disassemble the head by removing the top from the canister and then rinsing away any debris or soil that may be clogging it up.

Take out the screen basket as well and make sure to clean it thoroughly. Finally, adjust the watering range in the head before you reinstall it.

If the head isn’t the problem, it could be a matter with the valve. Make sure to check the backflow device of your sprinkler system; sometimes they can be closed off and will simply need to be opened.

Should the sprinkler head and the valve be in fine working order, there is a chance that you have a leak that is siphoning the water pressure from your irrigation system.

Start by leaving the water on and looking for any apparent leaks. Smaller leaks may be difficult to spot right away but once you find the source of leaking water, you can then move forward. As is the case when you do any work on the irrigation system, cut off the water supply.

Cut out the damaged portion of your sprinkler line. With the water off and the line open, put a clamp on one end of the line, putting a slip coupling over top, and then tighten the clamp.

Do the same thing for the other side and slip your new piece of PVC piping in between the couplings. Secure both and you should have a fully functional new piece of piping that should work for a long time to come.


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