Q. How far should the sprinkler line be from a wooden fence? Im gonna run lines next to a wooden fence all around the perimeter of my backyard. Fence is about 8 feet tall.
A. There are several issues here that come to mind. Most of this applies to walls as well as fences.
If your are using a trencher or [plow to install pipe the machine will likely not get closer than 18 inches to the fence. I would stay even further away, maybe as much as 3 feet. Both of these machines have a tendency to slip from side-to-side or get out of alignment when operated, especially by a inexperienced non-pro. You don’t want the machine to go through the fence.
One issue here is future maintenance should you need to dig up the pipe for a repair. You want enough room that you aren’t whacking the shovel handle (or your shoulders) against the fence if you need to dig. That would mean at least a foot of distance from the fence. Maintenance of the fence is another issue. If you spray water on the fence it will shorten the life of the fence, not to mention leaving ugly water stains on it. It is near impossible to remove water stains from a fence.
Sprinkler Heads and Water Stains on the Fence:
The sprinkler heads should probably be about a foot minimum from the fence. The closer they are, the more water they will get onto the fence. The water will
stain the fence and also shorten the fence life. To keep the water off the fence completely means the sprinklers have to be very far from the fence, typically at a minimum 24″ away for spray type, 36″ for the larger radius rotors. There are variables that impact that distance they need to be away from the fence. Different sprinklers have different amounts of accuracy as to the edge of the water pattern. Impact type rotors often spray a lot of water to the side, outside the normal watered area, thus they need to be very far away. In fact, with impacts I would say that you are not going to keep the fence from getting wet, period (unless you keep the head farther away than the radius of the impact sprinkler!) Also wind plays a huge factor in blowing water onto the fence.
Don’t Plant Lawn Next to a Fence!
When I want to keep a fence dry I plant a minimum 3 foot wide strip along the fence with shrubs and water them with drip irrigation (or use shrubs that don’t require irrigation). That way I can keep sprinkler watered lawn at least 3 feet from the fence so the sprinklers are at least 3 feet away. If the area is windy I go with 5 feet distance.
Generally it is considered bad landscape design to put a lawn next to a fence, unless it is an extremely attractive fence that you want to be a focal point of the landscape! Standard practice is to “buffer” the appearance of the fence with a shrub planter along the base of the fence.