Good water or bad water?
April 21, 2009 7:50 PM   Subscribe

My front yard slopes down from the street to our house and driveway. There's always a wet streak on the driveway where water from the yard is moving over the driveway to lower ground on the other side. I'm looking for a way to determine if the water is rain runoff or maybe is from our septic tank's field lines which are in the front yard. The amount of water increases after rain and slows down during drier times, but never completely stops. I've tried smelling the water and muddy dirt but I can't be sure one way or the other. Is there a cheap but reliable way of finding out what kind of water this is? Thanks.
posted by atm to Home & Garden (12 answers total)
A blacklight might be helpful: there's a lot of things that go into a septic tank that fluoresce under blacklight, while rainwater and dirt probably won't.
posted by AzraelBrown at 8:21 PM on April 21, 2009

you might try dyeing one of the water sources and then waiting.
posted by lapsang at 8:32 PM on April 21, 2009

If it never completely dries out then it's a spring or a man made water source.
posted by fshgrl at 8:41 PM on April 21, 2009

The presence of fecal coliform bacteria would tell you whether it's from the septic tank or not. Here's a DIY kit that should help.
posted by electroboy at 8:43 PM on April 21, 2009

To expand a bit on AzraelBrown's suggestion:

Trace-A-Leak Fluorescent Green Dye Leak Detection Tablets finds outflow leaks fast!
Your Price: $14.95; 100 tablets per bottle

On the trail of a septic or sewage system leak? Tracing outflow through water lines? Examining water flows and currents? Don't begin any work before you've confirmed the problem and pinpointed the leak origin. Simply drop one or more tablets into an opening ahead of the leak. The dye turns water a dense yellow-green color that is detectable over long distances of pipe, in water currents and in the soil of a septic field.

Trace-A-Leak dyes come in three colors: Fluorescent Green, Fluorescent Red and Brilliant Blue. All three dyes are used as a visual detection. The fluorescent green and red dyes can be detected with an ultraviolet light or by a fluorometer while the blue does not have these characteristics.

posted by jamjam at 9:48 PM on April 21, 2009 [2 favorites]

Increasing after rain is probably a red herring, indicating that it's a combination of rainwater and whatever is already leaking -- there's no good reason water should be anywhere if it hasn't rained lately. If you don't have a sprinkler system, it's surely either the septic line or the service line that runs from the water main to your house (both of which are your responsibility if you own it).

You can pay someone to do leak detection, but it'll run you a few hundred dollars, so dying the water sounds like a good DIY bargain. You'll have to spring to fix whatever's leaking regardless of whether it's the septic tank or not, though.
posted by cj_ at 10:42 PM on April 21, 2009

"there's no good reason water should be anywhere if it hasn't rained lately"

There is a common case, particularly in the Northeast US, of sequestered streams crossing yards, house foundations, and driveways. This often results from developers clear-cutting and bulldozing a housing subdivision. Small, natural watercourses will be covered but will still retain their original hydrology. This manifests as perpetually wet and seeping areas.

The dye test ought be done, but there is at least one good reason for natural flowing subsurface water. If the water is clean but annoying, French drains can be constructed to divert the flow. (I didn't know, but am unsurprised that the French drain was invented in soggy Concord, Massachusetts).
posted by fydfyd at 4:23 AM on April 22, 2009

Without knowing the full topography of your property it would be next to impossible for us denizens of the internet to know from whence the water comes. Using a basic assumption that the house is on the high spot then it would be obvious that the water is from the septic tank. Maybe it was even built on a spring? Dunno?

As has been said, testing the water is a damn good idea before you start drinking it. But poop water on the driveway isn't going to kill anyone. If you want to get rid of it, dig a trench on the upstream side of your driveway a foot wide x a foot deep. Put in a drain tile/perforated drain pipe and fill with open graded stone. Voila, water does not flow across your driveway anymore.
posted by JJ86 at 6:15 AM on April 22, 2009

It sounds like the water is probably not related to rainfall since it is continuously flowing (that is, assuming you live somewhere that doesn't get rain every day). My guess would be either a natural groundwater seep/spring or a septic line leak. To rule out the septic tank, the fluorescent dye idea sounds like a good start (although not necessarily definitive). Testing the stream for fecal coliform bacteria would also be useful. Does the grass or vegetation in the path of this runoff look greener or taller than the surrounding vegetation? If so, that's a good indication that the runoff is nutrient-rich and likely from your septic system.

If you determine the water is clean groundwater, a french drain on the side of the driveway is a good solution. But, I have to respectfully disagree with JJ86 that this would also solve the problem of a septic line leak--"poop water" probably won't kill anyone, true, but it is considered untreated sewage and I would guess that your local ordinance requires your septic system to be functional (not leaking). Also, ummm, it's nasty to have sewage running across your driveway.
posted by Jemstar at 7:31 AM on April 22, 2009

I'm going to disagree with both JJ86 and Jemstar for the following reasons:

1. Untreated sewage can kill you, although it's unlikely.
2. Dense clay soils can leach water for a long time if there's some sort of underlying drainage plane, like a sand layer, so it doesn't necessarily mean there's a spring or a septic leak.

Another possibility is that your water service is leaking. Are you on public water?

Also, if you're going to build a french drain, wrap the pipe and stone in a layer of filter fabric, otherwise you'll be digging it up to get the silt out in a few years.
posted by electroboy at 8:17 AM on April 22, 2009

"Poop water" on a driveway can kill you, sure, but it has to be a perfect chain of multiple events that you would most likely win the National Lottery twice before it happened. The chances are that you'd die by slipping on it well before ingesting it after putting your foot in your mouth. Let's be realistic though. The bottom line is the OP has no real information in the post for any of us to determine with any accuracy where the water is coming from. What-if scenarios are fun puzzles to play but they aren't worth losing sleep over or arguing intricate details.

To recap, given the OP has a leaky septic field and nothing else then it needs to be repaired which will fix the problem. Given the OP has a leaky water service and nothing else then it needs to be repaired. Given that the OP has an underground spring in their septic field then he should have it checked for bacteria and then install a wrapped pipe underdrain. Given that the water source is a surface flow from outside the property then a swale should probably be installed to check the flow. In any case, a good first step is to test the water.
posted by JJ86 at 9:40 AM on April 22, 2009

If the tests for fecal coliform come back negative, there's really nothing you have to do, unless you want to spend several hundred dollars to remove a wet spot on your driveway.
posted by electroboy at 11:07 AM on April 22, 2009

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