Mothballs for Drain Flies: Do They Work?

Mothballs, which contain 1,4-Dichlorobenzene or naphthalene, may eliminate adults flies. However, drain flies lay eggs and feed on the organic buildup in pipes. A less toxic approach would be to remove the breeding ground. This helps ensure total eradication without exposure to harsh chemical vapors.

Understandably, some homeowners like to try out different DIY methods. We outline the best approach to using mothballs to potentially eliminate, or at least slow drain fly activity.

What Are Mothballs?

Mothballs are small balls that contain a mixture of pesticides and deodorant. They are commonly used in clothing storage units and wherever protection from fabric-eating pests needed.

According to the National Pesticide Information Center, mothballs should not be used in open areas of a home. The long-term effect of pesticide and vapor exposure can be harmful.

Children or pets may also be at risk from the exposed chemicals balls. This is just one of the many reasons why we do not explicitly recommend using them to treat drain flies.

How Mothballs Work

Mothballs work by slowly releasing toxic gases that kill moths and other insects. Common ingredients include naphthalene or paradichlorobenzene, which are both highly toxic.

Many websites mistakenly claim that using mothballs to treat house or drainflies is a natural solution. This is not the case.

fumes from pesticides

When used anywhere but airtight containers, toxic fumes are released into the air. In addition to the long-term health risks from repeated exposure, mothballs have an unpleasant smell that can take 3 to 6 months to dissipate. This is the second reason why we do not recommend using them in your bathroom or kitchen.

One of our wise Facebook fans also pointed out that using mothballs or pesticides for purposes other than intended on the label is illegal. Additionally, the EPA reports that it is not uncommon for products containing naphthalene to be illegal. Due diligence is a must.

Treating Drain Flies

The theory on several other websites, is that drain flies (Psychodidae) are related to all other moth types. This makes mothballs effective. While we won’t dive into the inaccuracies related to entomology, the poison on mothballs will likely work a variety of insects. Regardless of family.


If your main concern was to get rid of adult flies, you can place several mothballs under a bowl that covers the drain. This traps the vapors and ensures all adult flies in the vicinity get a lethal dose.

This should cut down on drain fly sightings and activity. If you leave the mothballs long enough, you will hopefully continue to eliminate adults before they lay more eggs and continue the life cycle.

drain fly lifecycle

A better option is to treat the actual source of infestation. Drain flies feed on and lay eggs in the gelatinous buildup in drains and pipes. Removing this buildup is key to preventing ongoing infestations and recurrences.

Get Rid of Drain Flies Without Mothballs

The process of getting rid of drain flies without toxins that permeate your living space is simple.

  1. Identify where the drain flies come from
  2. Use a pipe brush to scrub inside the drain or pipe
  3. Use an enzymatic drain gel to further remove organic buildup
  4. Follow with an insect growth regulator, such as Gentrol, to break the life cycle
  5. Make sure drains remain free of blockages and buildup

The five steps above will save you from having to use toxic mothballs and praying the house won’t stink for months afterwards. If you have ongoing issues and cannot identify the source, check your toilet flange seal, or the sump pit in your basement.


While we promote a DIY approach to treating pest infestations, we also tend to err on the side of health and safety. As such, it is in your best interest to avoid using mothballs in open spaces, especially if you have children or pets. They are highly toxic, and may not solve the real issues in your drain.