This Is the Worst Time to Do Your Laundry (At Least in Some Cities)

Picture yourself on a rainy day. What will you do, if you don’t feel like venturing out in the bad weather? When it’s dreary outside, I usually hunker down and do household chores — running the dishwasher, catching up on laundry, maybe even taking a long shower and shaving my legs. 

These days, though, I take the opposite approach: I never do chores that require water use when it’s raining outside. That’s because I recently learned that my city, Milwaukee, has a shared sewer system — which means rainwater runoff, domestic sewage, and industrial wastewater collect in the same pipes. 

When it’s raining in a shared-sewer city, naturally there’s more runoff in the pipes. And doing water-intensive chores like laundry creates even more wastewater on top of that — enough to overwhelm the sewers, causing wastewater to overflow directly into waterways (in Milwaukee’s case, Lake Michigan). That’s not just bad for wildlife and natural ecosystems; too much wastewater in local rivers or lakes could also result in contaminated drinking water and potentially make you sick. 

According to Marissa Jablonski, the executive director at the Freshwater Collaborative of Wisconsin, depending on where you live, it may be best for your local waterways if you skip those chores when it’s raining and prioritize them when it’s not. For maximum effect, you can even plan ahead. If you live in an area with a shared sewer system, scope out the week’s weather on your phone and slot out a time for laundry on a dry day rather than rolling the dice and being forced to do it during a storm, when more water will accumulate. 

While laundry uses a lot of water, Jablonski says the same principle applies for other water-related tasks, like doing dishes and showering. If you can stand to wait until the rain stops (ideally, the next day) then do that. You can even stand to skip flushing until the rain stops if it’s raining a lot for a long period of time. And if you live in a snowy climate and spring is coming, you’ll want to put this principle into practice when the snow is melting.

Not my neighbor in Milwaukee? you may be wondering about whether this rule of thumb affects you. According to the Environmental Protection Agency, 860 American cities have shared sewer systems. Those cities include New York, Atlanta, and Philadelphia, plus others primarily in the Great Lakes and Northeast regions. You can check out this map from the EPA to begin to find out if you’re affected, or simply Google your city + ”CSO” to find out.

In general, if you have a septic tank at your home, you don’t have to worry about it — your sewage collects there rather than in a municipal one. If you do live in a place with a combined sewer, you may have a little more work cut out for you — but in the end, your community will be healthier for it.