# Septic Drain Field



## ekulrenlig (Sep 1, 2008)

I am planning a putting in a vegetable garden in my yard and am wondering if I need to be concerned about my septic drain field? Can I till and work the topsoil above the drain field? How can I determine exactly where my drain field is, what type of system I have, etc.? Also, is it potentially dangerous to grow and eat vegetables grown above a drain field?


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## Daniel Holzman (Mar 10, 2009)

The best way to know where your septic system is would be to review the approved as built plans for the system. If you do not have such plans, the only way to know where the system is and how it is constructed would be to dig up the system, unless it is a raised system, in which case it would be relatively clear the approximate boundaries of the system.

Digging up the system simply means excavating with a hand shovel until you hit the pipes. First you excavate the distribution box, and determine how many lines there are. You then trace the lines until they begin to run straight by excavating the down to the lines with the shovel. If correctly built, the pipes are bedded in sand, and are usually about a foot below grade.

There are special pipe location tools that I have seen used by professionals, consists of an in ground tracer that travels up the pipe, and emits radio waves that can be detected above ground. Pretty cool, but pretty expensive for finding a septic field.

You can certainly till above the field, provided you do not damage the pipes, so you absolutely need to know how deep they are before you start tilling away. As for the danger of growing and eating vegetables above the field, I have been doing it for 20 years, it hasn't killed me yet. But you may want to stay away from deep rooted vegetables. We grow lettuce, tomatoes, squash, cucumbers, asparagus, beans, carrots, strawberries, rhubarb, and the odd melon, so far no problems. If I die from septic system poisoning, I will post and let you know.


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## ekulrenlig (Sep 1, 2008)

Where would I be able to track down the "approved as built plans?"

Excavating with a hand shovel seems kind of hit or miss, and a lot of work.

Approximately how far from the house would the septic tank be located, and how far from there would the distribution box be located?


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## nap (Dec 4, 2007)

> =ekulrenlig;432212]Where would I be able to track down the "approved as built plans?"


if there was a permit pulled, the health department of the building department



> Excavating with a hand shovel seems kind of hit or miss, and a lot of work.


Yep, sure it. I would suggest a 1/4-3/8" steel rod preferably with a t handle welded on it. You can poke the ground once you figure out a general direction of the pipes out of the tank of distribution box.

also, if you use a rod longer than you need to be concerned with depth wise, you can simply use the rod to poke around the area you are considering for the garden so you simply know there is nothing any closer to the surface than the rod. You have to poke a lot though. It isn't that hard to miss a pipe that is less than 4' in diameter.



> Approximately how far from the house would the septic tank be located, and how far from there would the distribution box be located?


I have seen tanks immediately outside of a house and I have seen the 1-200 feet from a house. Not all systems use a distribution box and there is no way to know how far away it is from the tank.

Do you have a crawlspace of basement where you can see where the sewage line leaves the house?

Regardless of this garden, you really should know where your tank is. The do need to be pumped out occasionally.


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## ekulrenlig (Sep 1, 2008)

Hmmm, boy this garden idea is becoming more work than I thought.

Yeah I can see where the sewage line leaves the house in the basement. However, there was an addition built onto that side of the house which outside walls is just about right over where the sewage line leaves the basement.

Isn't there typically a lid or something on the tank, that should be relatively easy to find.


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## Scuba_Dave (Jan 16, 2009)

What about a raised garden ?


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## Daniel Holzman (Mar 10, 2009)

There is almost certainly a manhole cover on the tank, however the tank is often covered with soil, hence the cover can be hard to find, except by poking around. Check with you Board of Health, they may have the plans for the system, assuming it was reviewed and approved by the Board. If the cover is metal, you may be able to find the cover by using a metal detector, however this will fail if the cover is concrete as it sometimes is.


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## ekulrenlig (Sep 1, 2008)

Would there be some kind of evidence, like a small depression or something where the cover would be?

I realize I need to figure out where everything is before I go digging around, and not just make assumptions, but I'd like your opinions on this please. My yard has a 3-4 foot rise in elevation about halfway from the house to the back of my lot, and then dips back down in elevation 5-6 feet to the back of the lot. Wouldn't you think the drain field would be in the back of the lot where the elevation is lower than the house? If that is the case, then at the top of the "hill" any septic lines or the distribution box would be quite a ways beneath the surface, right? I was planning on putting the garden at the top of this hill. I may just end up putting the garden on the side of the yard where I am fairly certain is quite a ways from the septic system.


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## Snav (Aug 20, 2009)

Believe it or not - plans aren't always accurate or useful. I got the plans for this house and lo and behold if it stated we just had a leech field and NOT a tank - but amazingly - we have a tank that's older than the house and I'm having to repair the pipes on it.

Use the skewer/poker idea to find the tank - lots of poking - but it's unlikely that it's REALLY far from the house. Usually they're 10-20 feet away.


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## downunder (Jun 13, 2008)

Unless you are planning on tilling more than 6-8 inches, I wouldn't worry about that point. Field lines are much deeper than that.


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## nap (Dec 4, 2007)

Snav said:


> Believe it or not - plans aren't always accurate or useful. I got the plans for this house and lo and behold if it stated we just had a leech field and NOT a tank - but amazingly - we have a tank that's older than the house and I'm having to repair the pipes on it.
> 
> Use the skewer/poker idea to find the tank - lots of poking - but it's unlikely that it's REALLY far from the house. Usually they're 10-20 feet away.


I would suggest the plans you got were for what ever was put in at the time the permit was pulled. Since it appears the tank was pre-existing, it would not be within the permit and as such, not on the plans associated with the permit.

and yes, they are generally close but I have seen a lot of things and having a tank 100+ feet from the house should not be discounted. I have seen where a new house was built and the old one was used until the new one was finished. The new house was attached to the existing septic system. Since the new house was on the opposite side of the house as the septic system, it was whatever it was from the old house plus the distance the new house was away from that point


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## ekulrenlig (Sep 1, 2008)

Well, I've done a little bit of poking around and I think I have located my septic tank. There is a slight depression where perhaps the manhole cover is. It is maybe 15-20 from my house, and maybe 5 feet from the new addition. What are the approximate shape and dimensions of a typical septic tank? The house was built in 1980 if that helps.


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## AllanJ (Nov 24, 2007)

Typical septic tank dimensions, a rectangle 3 x 6 feet give or take. The most modern tanks have two, or even three covers in a row and in most cases they are all buried with no surface visible manhole cover.

In a properly working septic system there no sewage leaking out in the vicinity of the tank; it's all down at the leach field.


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## ekulrenlig (Sep 1, 2008)

On a side note: How do you know when/if you need to get your tank pumped out?


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## AllanJ (Nov 24, 2007)

Method 1. The contents of the tank consists of 3 things, solid material (at the bottom), liquid (in the middle) and greasy foam (called scum, at the top).
When the solid or the foam gets to too great a percentage of the total depth, whichever comes first, (I don't know the numbers offhand) then the tank really needs to be pumped out.

Method 2. Have it pumped out on a timed basis, for example every 3 years. Each time have the serviceman give you his opinion, whether the tank really needed it versus it was about the right time versus it could have gone another year or two. Use this information to shorten or lengthen the interval between pump outs, but you should be able to settle into a uniform time interval.


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## Daniel Holzman (Mar 10, 2009)

The best way to determine if a tank needs to be pumped is to open the cover, and measure the depth of solids using a wooden probe that you plan to throw away. If the solids are less than 15 percent of the depth of liquid in the tank, no need to pump. If more than 15 percent, time to pump. By the way, there is good evidence that a properly managed system can go upwards of 20 years with no need to pump. Specifically, no garbage grinder, don't toss bulky vegetables down the drain (compost them), use limited amounts of laundry detergent, you may never develop large amounts of solids.


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## Snav (Aug 20, 2009)

You should routinely pump, though, so the tank, baffles and inlet can be checked for fractures and other issues. A system can be relatively low on sludge but still have other issues that need to be addressed.


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