garden over a septic tank?

So there is an area of lawn at my home I want to turn into a garden but it is over the septic tank for the house. The first issue is that if there is any problem with the tank it must be dug up and therefor the garden with it. If there are no problems though I was looking for comments on whether the septic tank would pose health problems, or any other problems to the plants grown above it. Thanks

That is a good question. I also wonder if planting fruit trees, or a garden over a septic drain field would pose any health risks. I think planting over a septic tank, is that the tank will have to be emptied at some point, and the honey-dippers would wind up dragging their vacuum hose over your garden. I imagine it is not the cleanest of hoses. Also, I might speculate that any of the deeper rooting plants would try to get directly into the solid waste of the septic tank. Maybe this would pose a health risk. Anybody else have any ideas on these questions?

The important part of this is mapping the location of your drainfield - that is the area to avoid planting trees with big roots and root crops. You need access to the septic tank, and don't want trees over the top of that either, but I wouldn't worry about things like blueberries, currants, etc as long as you leave access to pumping..

well a septic tanks is different than a drainfield..so I will talk about JUST the tank area here for a bit.

at one time I had a greenhouse over my tank but since have moved it..

one thing I find very very very very very helpful is to THINK about what is down there..first of all put something over each of the tank holes..mine has a fabric over it to keep out sand but then has a thin layer of soil and then one of the tank covers (i have 2) has a bird bath sitting right on top of the hole cover..to mark it..the other has a wooden boardwalk over it..can be easily lifted and removed..steppers would also work, making sure you know what steppers are over the tank..or make a map.

then you can plant around the area..your best bet is a mediterranian style herb garden on the flat..no spiral..as the soil will be thin, dry and hot on the tank itself..I have sage, thyme, violets, sedum, creeping thyme, parsley, lamiums, etc ON the tank itself ..around the birdbath..then in the areas right next to the tank on the sides the soil is very deep and loose and is a good spot for something with a deep root, I have swiss chard, hollyhocks, and other deep rooted plants in those areas..around them I have some other salad greens and some ornamentals like daylillies and siberian iris, in areas that are a little farther away from the tank itself..

the tank here is in the middle of a garden bed..my beds are all mixed between food and ornamental crops and as you get away from the top of the tank and drainfield I even have incorporated things like fruit and ornamental trees and shrubs..I have some dwarf cherry trees behind my house away from the tank, and have lots of honeysuckle, lilac, spirea, barberry, etc.. on the downslopes of backfill as our drainfield is raised 4' above level as is our house all backfilled with very high quality soil..

you can see our drainfield garden in our blog

So from what I'm gathering here is that it is probably ok to grow plants with shallow root systems over the tank area. I was not planning on putting any trees or shrubs there anyways. I will have to do better research to see what plants have deep tap roots and avoid those. I figure if i plant mostly annuals then if a situation with the septic tank arises i wont loose perennial value, i just hope it doesn't happen during the growing season!

the tank itself isn't that large..you can use the tap root plants on either side..but not the back or front as the pipes are there..into the house and out to the drainfield.

herbs are very good over the septic as they can do well on thin soil and shallow soil with dry and heat..that you usually have there..if there is some shade, which we have on ours then you can even use other ground covers like violets..

there is no drainage "around" the septic tank itself..so there is no danger of bad stuff unless there was a spill..just that the soil will be thin on top..unless you have it buried quite deep..

if you make arrangements (like putting a bird bath or large stepper stone) over the lids..then you can plant anything that will use the proper soil depth that is there.

Start composting your humanure and then you can do whatever you want.

if you are talking drainfield rather than the cement tank..then you probably want to use a lawn or some other groundcover over the main drainfield..on ours I have a small circular lawn over the drainfield perse, but I also have fill around the raised 4' high drainfield that gradually slopes it down to the surrounding area..at about a 45 degree angle in most places..some steeper some less steep. I have these fill areas planted to shrubs, non invasive trees, perennials, grape and other vines incl roses and clematis..over arbors..

you can view the drainfield gardens in photos on my blog (see signature) the drainfield is on the north ..behind..part of our house and has become a beautiful garden..but I do keep the top free of plantings other than the lawn, for evaporation so the drainfield works properly

I don't have a septic system yet (I'm still looking for my homestead site) but when I do, I plan to have ordinary grass over the septic tank, mostly so I won't be too upset if/when my tank needs to be dug out.

My drain field will be loaded with dynamic accumulators (comfrey, vetch, etc.) These plants can be composted to provide high nitrogen to my gardens. I want to make use of the waste in my septic system, but I want it to pass through Mother Nature's kitchen one time before I do.

Chris; deep rooted plants will clog your leech pipes, disallowing flow, causing a system backup, resulting in your house becoming a the sewage leech field

I leave the area over my septic tank in grass and white clover. Needless to say it grows more quickly and more lush than the rest of my lawn area. I mow it regularly and feed the clippings to my cattle, hogs, and chickens, who devour them. In 2013 I just might turn some of it into small bag silage.

Eating vegetables grown over you septic tank is OK. Just remember that when they come to drain/clean it. the area will be contaminated for a while.
Eating nut/vegetable grown over your drain-field may not be ok due to the fact that they might be high in "bad" mineral/metal.
Eating vegetables grown over the drain-field is never a good idea due to the risk of do-do water on roots and do-do water splashes went it rain.
And the fact that the soil/water has bacteria/pharmaceuticals/heavy concentration of metals.
Planting nut/fruit trees next to the septic tank is not really a good idea. The roots can grow over 3 times the height of the tree.
So it might damage pipes and or the actual concrete over time. The drain-field is usually located near the tank and the roots might find it.
With roots in the drain-field, you will shorten the lifespan of the drain-field and possible absorb chemicals/metal into your crop.

I would however recommend, planting vines in it and then composting/mulch with the vine leave.
You might even completely kill the vine every few years, just to make sure the roots are in check.

I'd be interested in what people's experience has been with the relative safe distance regarding drain fields and edibles. I know Geoff Lawton has mentioned putting in reed beds as a filter but for some spaces it doesn't seem practical.

I have a relatively small draining area and I agree I wouldn't really want to plant anything over top of it because of the root scenario etc - but what about beside it? I guess it's one of those things that is most likely fine but there's the off chance it could not be fine.

It's just one of the more annoying parts about having a septic system and a smaller acreage because it steals a good chunk of growing space! I've eaten the wild raspberries next to the leaching bed and survived though, but for now I've just been throwing wildflower seeds there. Last year when I got the property I moved some compost into the space beside the leaching bed (which is an area where lawn meets forest) with the intention of growing stuff there and I got tons of volunteer edibles (huge pumpkins, squash, tomatoes etc) but I held off from eating because I just wasn't sure...It was a really productive space so it's kind of a shame.

Has anyone grown edibles NEAR or along side their leaching beds and not had bad experiences?

When I was at West Point I had a vegetable garden over the leech field and chemical analysis showed no issues. The septic system was maintained with Ridex every month and several chemists thought that was the reason everything was doing well with no contamination. Now a days there are even better options including worm farm composting in a dual tank septic system, this was developed by some Aussies. If at any time you think you have a problem, a simple soil sample sent to be tested will answer any doubts or it will show the problems so they can be corrected.

If you use oyster mushroom spawn in your gardens or over the leech field, they will take care of most all pathogens, if any escape the system un-changed.

I have been growing an annual garden over my leach field for 10 years. I am not recommending it, was just the best place for it. If i understand correctly it is a ''wetland system'' 60' x 60' x 2' deep gravel, buried under 2'ish of soil with 4 junction boxes. The junction boxes are never full, only one really ever has any water in it unless we get a lot of rain. In droughts that garden is as dry as any other of the gardens and the plants show it. so i don't think a lot of water sits in the drain fields too long. It is only 2-3 of us using the system so we are not taxing it and the worst chemical that goes in is laundry soap. Don't plant any root crops in there unless it is for green manure and we keep working on the soil so the roots don't need to travel (not that that will stop them). I think you just need to know what your system is and decide if it is worth the possible risk of a pathogen finding its way into your tomato and roots adding too much organic matter to your gravel. Grass can do a fair job of sending roots down as well. I also only use those vegetables for us or our animals. Good Luck

Hi!
So, I have a septic tank and decided to grow wild violets as ground cover. Then I learned that violets are edible and can be used to make syrup and tea. While I get the reasons not to grow vegetables over your tank, what do you guys think about violets as they would be boiled first?

It seems to me if they are boiled it should be for more than a moment, like dropping them into water that's been taken off the stove.  I'm not sure how long something should be boiled to kill all the germs, but that would be worth checking.

Sterlization requires 15 minutes at a pressure of 10 lbs per sq. in.. If you are not using pressure then boil for 30 minutes.

Agreed, sterilization requires specific time/temperature/pressure inputs. But given the human pathogens that might possibly be an issue, would pasteurization be adequate?

To my mind, growing over a septic tank has two issues:

First is the depth and quality of soil you have to work with. The fill used to backfill around the tank will be chosen to protect the tank, period. It is probably garbage from a growing perspective, with just enough topsoil to grow lawn. It will also dry out quickly because of the "concrete hard pan" beneath. Not attractive as a grow space.

Second, ANY plant that has powerful penetrating roots can cause major, enormously expensive damage. Many perennials and essentially all trees are a no-go anywhere on or near a septic tank. And it's not just the tank -- many jurisdictions require a full system upgrade as soon as you touch any component. Yikes.

End of rant. Choose carefully folks.