Dear PoPville – More Backyard Drain/Mosquito Troubles

“Dear PoPville,

I’m hoping there are some plumbers or engineers out there, or people who have dealt with this before, who can share their wisdom.

We live in a Petworth rowhouse, and we have a drain in our back yard. It’s fairly close to the back of the house, and the downspout from the roof appears to go into it. I always assumed that it was some kind of french drain – a french drain with problems, since there is always standing water in it. It is naturally a source of mosquitoes. We constantly throw dunks down it, spray it with cutter, etc. Our neighbors all have these drains, though, so it doesn’t make much difference.

Last week, some guys came to clean some debris out of the drain next door. My husband was chatting with them and found out that in fact it is not a french drain. The yard drain connects directly with the main sewage line in the house – the standing water is there to sort of seal off the opening and prevent nastiness from escaping. Knowing this, we want to plug the damn thing and get a rain barrel.

Two questions for the PoP community: if we just throw some gravel down there, and then top it off with cement, is that okay? I don’t want to do serious damage to something in the house. And two: is there any way to get a count of the number of these drains still in existence, as a first step to getting them abated? I think that would virtually eliminate the mosquito problem in many parts of the city. Anyone have any experience with that kind of thing?”

30 Comment

  • For starters you should just buy some screen window screen and wrap the plastic cover with that. It will require frequent cleaning so that the screen does not get clogged with debris, but will keep mosquitoes out. I would DEFINITELY not put gravel in it until you have had a plumber look at it unless you are 100% sure that it is at the end of the drain line. Other drains may feed through this one and clogging this one could cause serious backups into basements among other places

  • call dc water and sewage… they’re good about coming out in a short period of time to assess… have your plumber there as well. we had a similar situation on my street and whatever dc wasa + plumber took care of the whole situation.

  • Whatever you do, don’t just start filling it in with gravel! Good gravy, that could really screw everything up. If it’s a functioning drain I would keep it functioning.

    Unless this drain is exclusively for the gutters, it is likely draining water from around the house as well. If it’s anything like ours, once it plugs up the basement is at much greater risk for flooding.

  • A rain barrel will have the same mosquito problem as an open drain.

  • Not sure how the rain that falls on the concrete and grass will get into the rain barrel? That water needs to drain also.

    • The rain from the downspout (from the roof) goes into the rain barrel. But yes, if the drain is in the lowest spot of the yard blocking it will cause a pool to develop from the lawn/concrete runoff.

  • why cant you just cover the grate with a double layer of screen in the meantime?

  • Throwing anything down that drain is creating the potential for major sewer backups under your house!

    If you want to close it, cover it but do not pour / fill / throw / jam… anything down there!

    also make sure that your yard slopes away from your house before you cover that drain…

  • anon. gardener

    Hi, I’m the OP. Did some googling – found this:
    Nice to know there’s a program that’s attempting to address the bigger issue.

  • Fill it about halfway with Pop Rocks, you can probably buy them in bulk on eBay, then pour a gallon of Diet Coke in and see what happens. 😉

  • anon. gardener

    that actually sounds like a lot of fun. and would probably kill a lot of mosquitos.

  • anon. gardener

    I should also say we’re at the top of a hill and have zero problem with moisture/ flooding. the whole lot and all surrounding lots have excellent drainage.

  • So we have a similar setup with concrete patio and drain, and the dunk tied to a string (other end of string tied to drain cover) seems to help immensely. We get eaten alive out front but not as bad in back.

    We installed a rain barrel for roof runoff and I had to take a class to get this barrel & city rebate– barrel ends up costing $40 (

    From the class I took, I learned that my roof (average row house, ~600sf roof) will overflow a 60 gallon barrel with less than 1 inch of rainfall! That means just one good soaking rain will fill the barrel. So the rain barrel should not be the only answer to roof runoff. RE mosquitoes in the barrel, the one referenced in the link above has openings in the top for water to flow in, and a metal mesh screen across the top. The trainer indicated this was sufficient to keep mosquitoes out, and so far so good.

  • Seems awfully silly to plug anything that is meant to connect your property to the storm drain, even if you have otherwise good drainage on the property.

    I have a similar drain on my property, and I can tell you that the one time it got clogged, I had a flooded basement. It was not good news.

  • anon. gardener

    I don’t really see the point of this drain – I have a yard, with grass, it all slopes away from the house, and I am planning a rain barrel for the down spout and a rain garden at the end of the yard for the over flow… I can’t imagine getting enough rain to flood the basement, though I suppose anything is possible. Frankly, if it rained that much, we’d all be floating away.

    Maybe I’m being blind to something here. All I can really see is standing water and mosquitos. I’m originally from the real south – it blows my mind that someone would actually design a drain to have standing water.

    • Seriously? It’s called a trap. Your sinks all have them, tubs and showers too, washing machine, that’s a yep, and don’t look now, but your toilets are all really just big huge traps, or drains with standing water. This is one of the most basic tenets of modern plumbing and keeps sewer gas at bay.

      • Anon is completely right. It’s a trap. They’ve been used in plumbing for a hundred years so houses don’t fill up with sewer gases. Leave it alone. It’s working fine.

    • oh jeez.

  • You will not be able to replace that drain with a rain barrel. There is much much more water coming off your roof than a rain barrel can contain — in the thousands of gallons.

  • Call 202-612-3400 – DC WASA – they will come out and figure it out, maybe do it for you for free

  • put dragonfly larvae in the water inside the drain. they eat the mosquito larvae.

  • You don’t have a problem except in your imagination. Leave well enough alone. Thinking the drain is a mosquito problem that’s worth screwing up your house’s waste line is not weighing things correctly. Would you rather deal with a minuscule amount of mosquitoes or sewage backing up into your house?

  • it’s called a sludge well and is meant to be cleaned every year or two. the idea is that runoff from drains and yard are directed to the well. heavy sediment falls to the bottom of the well and water rises and exits a line usually on the opposite side. this keeps debris out of the sewers.

  • anon. gardener

    Yes, I’ve come to the realization that as much as I’d like to eliminate the toilet in my back yard, the city infratructure prevents me from doing so. So sad. I’m mulling over a few ideas, and I’m going to see what people do in other cities with combined sewer systems. If I find anything interesting or useful, I’ll share the info.

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