Beautiful smiling young woman washing the dishes in modern white kitchen.

Is Dawn Dish Soap Safe for My Septic System?


When it comes to cleaning products, there’s nothing more iconic than a bottle of Dawn soap. The bright blue liquid is advertised to be gentle enough to clean baby ducks and strong enough to cut grease. Many people even use it for non-dishwashing purposes, like removing soap scum or fighting weeds.

Needless to say, the popular soap is touted as a mild dish liquid that can do no wrong. But is Dawn safe for your septic system? Let’s look at what you need to know.



Dish soap has an innocent reputation. It’s an ordinary household product, after all! The soap is also sold everywhere and leaves your dishes squeaky clean—what harm could it possibly do?

As it turns out, it can seriously damage your septic system. Like many household items, conventional dish soap is more likely to contain harsh chemicals and non-biodegradable ingredients. This could take a toll on your system’s well-being over time.

Specifically, household products can disrupt the levels of natural bacteria in your tank and drain field. These bacteria break down organic solids and filter wastewater. Without healthy amounts of bacteria, your septic system can’t properly do its job.

Harmful chemicals might also contaminate the groundwater and surrounding soil, which can upset the environmental integrity of your property.

Phosphates are major culprits, but anything that’s petroleum-based or anti-bacterial can pose a problem, too.
There’s also the possibility of septic clogs and backups. If certain ingredients aren’t biodegradable, they can eventually accumulate and clog your septic system.



Dawn produces many cleaning products. For the purpose of this article, we’re going to focus on Dawn’s Ultra Concentrated Dishwashing Liquid. This is the classic blue dish soap labeled as “original,” which most people are familiar with.

And when it comes to your septic system, Dawn may not be the safest choice.

While the soap is free of phosphates, it’s not clear if it’s fully biodegradable. Dawn’s FAQ page states that their products have biodegradable surfactants—but they don’t mention the remaining ingredients.
According to the product’s ingredient list, the soap has:


  • Sodium lauryl sulfate. Sodium lauryl sulfate, a surfactant, is listed as an environmental toxin (and irritant to humans) by the Environmental Working Group (EWG).
  • Sodium laureth sulfate. Sodium laureth sulfate is also used as a surfactant. The EWG lists 1,4-dioxane (an environmental pollutant) as a contamination concern of this ingredient.
  • Methylisothiazolinone. In Dawn, this acts as a preservative. But according to the Environmental Protection Agency (EPA), methylisothiazolinone is “moderately to highly toxic” to marine and freshwater organisms.


Dawn also has a “D” rating on EWG. This is based on factors like “poor ingredient disclosure” and “potential for aquatic toxicity.” Furthermore, back in 2010, it was revealed that Dawn soap was petroleum-based.

Now, the formula may have changed since then. There also isn’t any specific research on how Dawn specifically affects septic systems. However, based on the available information, Dawn may not be the safest choice.



To err on the side of caution, use more natural dish soaps. Look for products that are biodegradable and free of the above ingredients. While you’re at it, avoid antibacterial formulas, which can harm the friendly microbes in your tank.



It’s true that Dawn isn’t as harsh as other soaps. Yet, there are definitely safer choices on the market. Our technicians can provide recommendations at your next septic appointment.

We can also discuss other products that are toxic to your septic system. With our guidance—and regular pumpings—you can keep your system healthy and well.

Paradise Valley Septic offers residential and commercial septic service throughout the Phoenix area. Contact us at (480) 351-1725 to schedule an appointment.


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