Can Sprinkler Systems Cause Problems With Household Plumbing?

What Happens When Sprinklers Turn On

• It's important to understand how the sprinklers interact with your home's plumbing. When you turn on the sprinklers, water is diverted from the main supply line into the sprinkler manifold. The timer sends a signal to a series of valves inside the manifold, which then diverts water through a series of underground pipes to sprinkler heads on specific zones. Water continues to be diverted from the main line until the last zone has completed its cycle.

Reduced Pressure

• While the sprinklers are on, they are using water pressure from the main water line to operate them. Most sprinklers use about 60 psi of water pressure, which is the normal amount of water pressure for a residential system. But the use of that pressure reduces the overall amount of water pressure that's available to the rest of your system. If you run the shower while the sprinklers are on, you will notice a reduction in the flow of water from the shower head. That's because the system is sharing the limited amount of pressure between the sprinklers and the shower. The same reduction impacts the dishwasher and laundry machine. This is a temporary problem and only continues as long as the sprinklers are running.

Backflow Prevention Problems

• Once water comes in contact with the sprinkler system, it's no longer considered potable. All sprinkler systems are required to have a backflow prevention device installed at the front of the manifold. These devices prevent water from flowing back into the main line once the water has already reached the inside of the sprinkler manifold. If the backflow device on the sprinkler system has failed, it may cause water to run back into your household plumbing. If that happens, water can taste bitter as it has come in contact with PVC cement and other chemicals inside sprinkler pipes. It's important to stop using your water immediately and have a professional check the system, repair the backflow device and flush out the system.

Adjusting Water Pressure to Compensate

• If you must run the shower or other appliances that use water inside the home at the same time as the sprinklers, you can improve the performance of both systems by increasing the amount of water pressure that's released into your main line. The water pressure regulator valve sits on the main water line ahead of where it branches off to the sprinklers. This device has an adjustment valve on top that can be turned clockwise with a screwdriver to increase the amount of pressure that's released from the water utility to your pipes. While most regulators are pre-set at 60 psi, you can safely increase the amount up to 80 psi. This will help improve the function of both the sprinklers and the household plumbing.