A rain barrel looks simple, but the water in it is a mix of whatever the roof, gutters, and air have left behind. In St. Louis, spring storms wash pollen and dust off roofs, and summer brings leaves, bird droppings, and insects into the gutters. The water can change a lot from one storm to the next, so it helps to know what you are working with before you decide how to use it.
Why Rain Water Is Not the Same as Tap Water
Tap water in St. Louis is treated and tested on a regular schedule by the water provider. Rain water collected at home is not. Nobody checks it unless you do. That does not mean it is unusable, but it does mean the results are your responsibility, and the answers depend on your roof, your gutters, and where the barrel sits.
Start With What the Roof Is Made Of
The material and age of your roof matter more than most people expect. Older asphalt shingles, metal flashing, and painted trim can shed small particles over time. Some older paints contain lead, and some metal parts can release metals into runoff. If your house is older, or the roof or trim has been patched, repainted, or re-coated, treat that as a reason to test for metals before the water goes on food plants.
Look at the gutters too. Leaves, seed pods, and grit collect there and break down into the barrel. A leaf guard or screen at the downspout keeps out most of that debris, but it does not remove everything, and it does not catch fine dust.
Know the Common Test Options
- Basic field kits can show general readings such as acidity and hardness, which help you understand how the water may behave on hard surfaces and in soil.
- Lab testing for bacteria, such as coliform and E. coli, shows whether those organisms are present in your sample. Labs serving the St. Louis area can run these tests and usually provide a sample container and written instructions.
- Metals testing, including lead, is best done by a lab, because field kits rarely give reliable answers for metals at low levels.
How to Collect a Clean Sample
- Use the container the lab provides, or a clean bottle that has never held chemicals, oils, or cleaning products.
- Let the first portion of water run out of the spigot and discard it, so the sample is not stirred up from the bottom of the barrel.
- Fill the container without touching the inside of the cap or letting it touch the ground.
- Label the sample with the date, the source, and whether the barrel was recently refilled or had been standing for a long time.
- Deliver the sample to the lab promptly, following their storage instructions.
Match the Use to the Results
Rain barrel water is most often used for ornamental flowers, shrubs, and lawns. That is a sensible first use once you know the basic readings and have confirmed that your roof is not adding metals. For vegetable gardens, many homeowners keep rain water on the soil rather than on the edible parts of plants, and they wash produce with water from the tap. Let your own test results guide the choice rather than a general rule.
Keep the Barrel in Good Shape
Keep the lid tight and screened so insects and animals stay out. Scrub the inside once a season with plain water and a brush, and avoid soaps or cleaners that could leave residue. Stagnant water in a closed container can develop odor and algae, so use the water steadily through the warmer months rather than letting it sit for long periods.
When to Test Again
Retest after any change: a new roof, a repair near the gutters, nearby construction, or a noticeable shift in color, smell, or sediment. Seasonal patterns in St. Louis, such as spring pollen and late summer storms, can also change what ends up in the barrel, so treat each test as a snapshot rather than a permanent answer.
Keep a Simple Record
Write down what you tested, when, which barrel, and what the water is used for. A short log makes it easy to tell whether a change is new or simply ordinary. If a lab result raises questions, ask them to explain it in plain terms, and avoid judging the water by a single number out of context.