If you run a sprinkler system in a St. Louis yard, the water coming out of the heads deserves the same questions you would ask about the water in your kitchen: what is in it, and what will it do over time? Lawns and garden beds absorb less than people expect, and anything dissolved in the water tends to stay in the top layer of soil. Here is a plain way to check before you spend a whole season watering with it.
Start With the Source
Many St. Louis homes take irrigation water from the same supply that feeds the kitchen. Some have an outdoor spigot connected ahead of the water softener, and others have an irrigation line added later on a different branch. Find out which one you have, because the answer changes everything. Check whether the house has a softener, and whether the outdoor line was tapped before or after it. If you have a private well, the water may carry different minerals altogether.
Watch for Softened Water
A softener swaps hardness minerals for sodium. That water may suit showers and laundry in many homes, but it is a poor match for a lawn. Over time, salts can build up in the clay soil common across the St. Louis area, and grass and shrubs may struggle to keep up. If your irrigation line sits after the softener, consider moving the connection or using a different outdoor source. Ask yourself whether you have noticed a white crust on the soil that stays visible long after it dries.
Simple Checks You Can Do Yourself
- Look at the spray pattern on the driveway and sidewalk. Rust-colored or brown marks suggest iron in the water.
- Watch for white, chalky residue on sprinkler heads and valves. That usually points to hardness minerals.
- Notice whether patches of lawn turn yellow or thin out even with normal watering.
- Smell and taste the water from the spigot. A rotten egg odor or a strong chemical taste is a reason to send a sample to a lab before you water plants with it.
When to Send a Sample to a Lab
A home test kit gives you a rough picture, but a certified lab gives you results you can act on. For irrigation, ask the lab to look at the items that matter for plants and soil: total dissolved solids, sodium, hardness, iron, and pH. If the water comes from a private well, add bacteria and nitrate to the list. Collect the sample from the outdoor spigot you actually use, not from the kitchen tap, and let the water run briefly before filling the container. Test during the same season you plan to water, since supply conditions can shift the results.
Confirm Backflow Protection
Any sprinkler system connected to the home supply needs a backflow prevention device. Its job is to keep irrigation water, which may carry fertilizer or soil residue, from flowing back into the drinking water. Look for the device on the line near the spigot or in the valve box. Make sure it is not damaged, buried, or wrapped in a way that blocks access for testing. Local rules can apply in St. Louis and nearby communities, so check with your water provider or local building office before you change anything. If the device is missing, do not install a substitute on your own. Ask a licensed plumber to look at it.
Fertilizer and the Sprinkler Line
If you feed your lawn through the sprinkler, mix fertilizer on a dry day and follow the label directions for watering it in. Do not let fertilizer solution drain back toward the spigot or into the line. Keep a short note of which zones receive which products, so you can match any lawn problem to a likely cause.
Decide What to Do Next
- Find out whether your irrigation line comes before or after the softener.
- Run the visual checks and write down what you see on the driveway, the heads, and the turf.
- Collect a sample from the spigot you use and send it to a certified lab for the list above.
- Confirm the backflow device is in place and in good repair.
- Compare the results with the condition of your lawn before you change your watering schedule.
Testing first takes less effort than reworking a lawn after a season of salt buildup or staining. For most St. Louis yards, a little information now gives you a clear answer about what to water with, and what to keep off the grass.