Is it wise to setup a gray water system when you have a septic tank?

November 4, 2007 7:57 AM

Is it wise to setup a gray water system when you have a septic tank?

We live on 2.5 acres in Colorado. We have a well for our water supply and a septic system for the gray/black water.

I've been researching setting up a gray water system. However, I don't know if this would have a negative effect upon the septic system. And I can't find an answer anywhere via Google.

Is the gray water volume necessary for the correct functioning of the septic system?

posted by TauLepton to home & garden (8 comments total)

I just had my septic drainfield replaced (at great expense) and one of the options the septic contractor mentioned was a separate grey water tank. He said it could potentially double the life of the septic drainfield. I passed due to the additional plumbing expense and disruption inside the house.
posted by deadmessenger at 8:14 AM on November 4, 2007

This page seems to indicate that installing a gray-water system would actually decrease the load on a septic. They seem to say this in a positive manner.

This site declares outright that separating black and gray water would actually help your septic.
YMMV.
posted by Thorzdad at 8:15 AM on November 4, 2007

It could be done, but it depends on the grading of your site: you should speak to a sanitary engineer (not just your contractor) before you do this, definitely money well spent.
posted by DenOfSizer at 8:17 AM on November 4, 2007

Is it wise to set up a gray water system ... I can't find an answer anywhere via Google.

Yes. Wise and good. Your system will work just fine with reduced waste water if it's been designed correctly, which means you're having it done by people who've done it successfully before and it isn't just cobbled together by a plumber new to the idea.

I think you're having trouble finding an answer through Google because it isn't a problem.

As always, though, be very careful about messing with blackwater. If you fall into that quagmire, you might never get out.
posted by pracowity at 8:18 AM on November 4, 2007

Since the recommendations for caring for a septic system recommend reducing water use, esp. graywater, it makes sense. Find the Cooperative Extension Office in your area; they're great with this sort of question.
posted by theora55 at 9:19 AM on November 4, 2007

I would imagine if you're flushing a toilet into the black water system then it's not going to be a problem. RV tanks do it that way just fine, and a bunch of sink and laundry water isn't necessary. Thumbs up on the gray water system -- we are doing that with a house we're building.
posted by rolypolyman at 9:51 AM on November 4, 2007

My family's home has a septic tank for black water and a soakaway/separate system for grey water. The soakaway needs maintenance every few years, the septic tank once in 25 years. Neighbours who don't use this kind of system, and put everything down the one pipe, need to get their septic tanks pumped every year or two. YMMV but this suggests to me that in the case of a septic tank, the less that goes into it, the better.

I believe it's also better not to put anything too nutrient-rich down a grey water system, so no garbage disposal in the kitchen sink, but I have only anecdotal evidence for that (someone's grey water drains persistently smelled bad, they stopped putting so much crap down the sink, the smell went away) and wouldn't know where to find anything else, so, ask someone who knows what they're talking about before doing it. And yay for thinking about this sort of thing.
posted by Lebannen at 9:11 AM on November 4, 2007

Then we're a go. I'm so excited about this idea. We live on the side of a mountain, so gravity-fed is a non-issue.

Now to go sketch out where to put the wetlands (what an odd concept for this area) and pump for watering the garden.

Many thanks to all who answered me. I *heart* mefi.
posted by TauLepton at 9:28 AM on November 4, 2007