If your St. Louis home has an in-ground sprinkler system, there is a device near the point where the irrigation line connects to the house water supply. It is usually a backflow preventer, and its job is to keep water from the irrigation system from flowing back toward your household supply pipes. When it works, nobody notices it. When it starts to fail, the first signs are often wet ground, a hissing vent, or a zone that runs when it should be off.
Find the device first
Backflow preventers come in a few styles. Some sit above ground inside a protective box or on a short section of pipe with shutoff valves and small test ports. Others are mounted higher, with a vent that opens to the air if pressure drops. If you cannot find it, look along the exterior wall near an outdoor spigot, or trace the irrigation supply line back toward where it leaves the house. If you still cannot locate it, ask whoever installed the system or your irrigation service provider.
Do a dry-day walk-around
A dry day is the best time to look, because wet ground is easier to read. Check these things:
- Standing water, soft soil, or mud around the base of the device.
- Staining or crust on fittings, which can point to a slow drip that has been running for some time.
- Valve handles that are intact, move freely, and are not seized in place.
- Mulch, rocks, or landscape edging packed tightly against the enclosure, which can trap moisture and hide early damage.
- Any sprinkler zone that runs on its own, outside its normal schedule.
Watch what the vent does
On some designs, a small amount of discharge from the vent during a watering cycle can be normal. Steady dripping or a constant hiss when the system is idle is a different matter. That usually means water is getting past a seal or check component that should be holding it back. Note when the sound or drip happens, whether a zone is running at the time, and how long it continues. Those details help a technician narrow down the cause quickly.
Plan around St. Louis winters
Freezing temperatures can crack a backflow body that still holds water. Before the first hard freeze, the irrigation lines should be drained or blown out, and the device should be protected according to the manufacturer's instructions and your irrigation provider's guidance. Ask the provider directly whether the backflow device is included in the winterization work. Many homeowners assume it is, and the answer is not always the same across service visits.
Check local testing rules
Local rules can require backflow devices to be tested by a certified tester on a regular schedule, with results filed with the water provider or municipal office. Requirements can vary depending on where your property sits in the St. Louis area, so check with your local water provider or municipal office instead of relying on a neighbor's experience. If you receive a notice about testing, do not ignore it. Keep a copy of every test report with your home records so you can show it at a sale, a permit visit, or the next service call.
When to call a certified tester
Call a certified backflow tester or an irrigation technician if you see steady discharge from the vent while the system is idle, if the device is cracked or leaking, if the ground around it stays soft after a dry spell, or if a zone runs without any scheduled reason. Those are signs that the device needs an inspection and possibly repair or replacement. Do not try to disassemble the device yourself, and do not shut off or bypass it as a workaround, because that removes the protection it provides.
What to do this week
- Locate the backflow device and note its location.
- Walk the area on a dry day and look for the signs listed above.
- Clear mulch and debris away from the enclosure so it can be seen and inspected.
- Check your irrigation controller for any zone that runs outside its schedule.
- Call your irrigation provider or a certified tester if anything looks wrong, and ask about winter protection and local testing requirements.