We have what I think is a rat, or family of rats, that are coming out of an outdoor drain. The outdoor drain is connected into our interior drain system. They chewed through the drain cover, I replaced it and they came through again.

I am in DC so the city sewer system is connected to the surface rain water system and rats are a known problem.

I am worried that sealing the drain in a more aggressive fashion will result in the rats coming out someplace else and would prefer that not to be in my house. The basement drains and plumbing are all buried in the foundation slab and connect to the main drain stack below the main clean out.

enter image description here

What is the proper solution to handling this?

  • You can try a metal drain cover, hopefully they won't be able to chew through that.
    – Eli Iser
    Aug 22 '18 at 14:59
  • @EliIser wouldn't that just trap them in the drain line and then have them come out someplace else (like the toilet)?
    – StrongBad
    Aug 22 '18 at 15:13
  • 1
    Back up your truck and attach flexible metal duct to your tailpipe with a hose clamp. Direct the exhaust into the drain line (don't worry, exhaust won't enter your home because your indoor drains are equipped with traps to prevent that). Deliver a good dose of exhaust down to the nasty rat family (don't be empathetic, they caused the Black Death plague). They will go somewhere else. Aug 23 '18 at 2:38
  • I came to this question from the weekly newsletter. I regret clicking that link. Aug 23 '18 at 19:31

Your drains likely do not go to sewers, they likely go to storm drains or gutters in the street. So putting Drano is going to put in directly into the environment, where it can harm your kids, your neighbor's kids, your pets and neighbor's pets etc. etc. etc. PLEASE refrain from taking that bad advice...

The rat poison is similar. The reason you don't see the dead rats with that is because it makes them intensely thirsty so they seek out water, then die there. Unfortunately things like raptor birds and other wildlife end up eating the dying or dead rats and get poisoned too.

Get rat traps and bait them with candy bars, preferably ones with peanuts like Snickers bars because they smell stronger. Once you get them all (assuming its a family), get rid of those cheap plastic grates and replace them with metal ones.

  • Code be damned, the outdoor drain is connected to the sewer system. That said, I am not a big fan of poisoning them. That said, it sounds like DC Water and Sewer might be willing to bait the main sewer system.
    – StrongBad
    Aug 23 '18 at 0:08

Kill the rats, then replace the drain with a metal cover.

rat poisonhttps://www.amazon.com/Motomco-Tomcat-Bait-Chunx-Pail/dp/B005BV0DD2

I can't say where the rats live, nor if they are coming or going. I can't think of a great way to keep them out of your internal drain system, and you're right you could end up with a rat in the toilet.

My solution assumes there is a less than infinite quantity of rats. If you put the rat poison down in their activity area, they will eat the poison and die.

As far as how exactly to put the poison down, I'd cut a hole in a whip cream container and put a couple chunks in there. Put the trap near the drain opening. You probably won't see dead rats around, but if you see they're nibbling on the poison, it's working. Leave the hole and keep refilling the poison until they're not eating it anymore, then try sealing it again.

You could get fancy and try to install a removable drain cover, then you could attach some poison to the underside of it, in the actual drain line. They do this with manhole covers.

If the rats are neverending, it's probably time to hire a professional.

  • My thinking is the rats are are living in the sewer system and were simply "escaping" through the drain. Do you think they are living in the yard and going into the drain? If they are living in the drain, how do I kill them?
    – StrongBad
    Aug 22 '18 at 15:22
  • Set snap traps in protective boxes near the drain. Aug 22 '18 at 15:58
  • you could try caustic soda or drano in the drain line, lots of it and heat the line with hot water first.
    – d.george
    Aug 22 '18 at 17:13
  • 1
    With luck, you can kill some neighborhood cats or raptors too. Aug 22 '18 at 23:45

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.