Locating septic leach field

seapea · Jul 4, 2005

Does anyone know how to locate a leach field? I know around where it is, but want more precise location information because we may be putting up a structure close by. I know the direction the line runs out from the septic tank. I also know it intersects the corner of the leach field at a 135 degree angle.

I suppose I could start trenching with a backhoe around 30 feet away from the septic tank until I hit gravel, and then follow the gravel until I reach the corner of the leach field. However, I was hoping for something less intrusive. Is there any way to detect the presence of the leach field (please, no divining for water suggestions).

Junkman · Jul 5, 2005

Depending on how old your system is, your local health department might have the original plans of file. If that isn't a viable alternative, then try to borrow a metal detector and see if you can locate the distribution box. Usually they have a handle on top made of rebar, so the metal detector will pick it up. You can also look for the area that the weeds or grass appear to be greener in color than the surrounding area, since they are nourished by the water from the system. Also, you might ask the neighbors who the local installer is that was used when it was installed. A little detective work will save you a lot of digging if you approach this with a open mind.

DKinWA · Jul 5, 2005

You can use a smooth metal rod to probe the ground to find the gravel in the drainfield. If the ground is really hard, you can water the day before or drive the rod in with a hammer. I've got a couple that I use made of 3/8" stainless steel rod with handles welded on them. Around here, gravity systems are typically 18-30 inches deep, so they aren't too hard to find. It helps if there's a point on the end of the rod that isn't too sharp but slightly larger in diameter than the rod itself (less friction when pulling the rod out).

It helps if you use some string and paint to lay out a grid and start probing. Our laterals are 36" wide so a grid on 18-24" usually works fine. It's a lot of work, but it's doable.

On edit:
Junkman has some good suggestions and I'd try them first. I outlined what I do as a last resort if I don't come up with anything using his suggestions.

seapea · Jul 5, 2005

I should have mentioned that the leach field 6' or more deep, so there is no way to probe for it, and there are no visible signs of it terms of faster growing vegetation. Also, I doubt a metal detector would work that far deep when trying to locate the distribution box.

There are few reasons it is so deep. First, the house was originally built for a person in a wheelchair, so it is very low to the ground. There are no steps into the house, even from the garage. Rather than grading up to the house, they just kind of dug a hole for it. Makes for a very wet and cramped crawlspace. Also, the house is very long, with a bathroom on one side and the septic tank on the opposite corner. As a result of all this the septic tank if quite far below ground, and the pipe that drains out of the septic tank to the leach field is out 3' to 4' below grade. Add to this a slightly uphill slope to the leach field and about 100' of distance, and I figure the leach field must be at least 6' deep.

I do have the original plans to the house, which do show the leach field and septic tank. However, the builder deviated quite a bit from the plans in terms of how things are positioned. The house was moved, the septic tank ended up much closer to the house, the utilities are on the opposite side of the house than shown in the plans, and the well is about 10' off. Because of all this, I doubt the leach field is exactly as show, although it is in the general area.

I'll contact the county and see if they can help. The house was built in 1976.

Junkman · Jul 5, 2005

I can't imagine a leach field that was approved being 6' below ground. 2 - 3 feet below the surface is the norm. In fact, with the leach field that far below grade, I can't see how there can be any evaporation from the system at all and the water has to be just filtering down into the rest of the aquifer, which isn't a desirable condition. Have you had your well tested for coliform bacteria recently??????

seapea · Jul 5, 2005

( I can't imagine a leach field that was approved being 6' below ground. 2 - 3 feet below the surface is the norm. In fact, with the leach field that far below grade, I can't see how there can be any evaporation from the system at all and the water has to be just filtering down into the rest of the aquifer, which isn't a desirable condition. Have you had your well tested for coliform bacteria recently?????? )

Well, it is what it is. I just called the county and they have records for both leach field installations: the original in 1977 and the 2nd field put in 1992. I'm waiting now for them to be faxed.

I know exactly where the newer field is because it has inspection pipes at the corners (4" capped drain pipes that stick up out of the ground about 18"). I've dropped a tape measure into them. The nearest one hits some muck at a bit over 6' (not counting the 18" sticking up). The ones that are furthest up the grade are closer to 7'. I'm assuming the pipe is at least another foot below them, so that's why I've been saying they are 6' to 8' deep.

As for leaching into the aquifers, wells around here are about 100' deep. Also, I think no matter how deep your leach field is, the presumption is that it leaches into the aquifer. If it didn't, that would imply that the flow of water in the area is up towards the surface, not down towards the aquifer. I don't think upward flow is typical except in very dry regions.

I've never had the tank tested for coliform. I've also never heard of having this done. If it did have coliform, I would assume there is no way to get rid of it. Also, it seems like coliform would readily spread to pretty much ever septic tank in the area via the septic pumping service, unless they sanitize their equipment between each service.

erich · Jul 5, 2005

I'll probably get in trouble for this but here goes. I am not sure what your aversion to divining for water is but as a born again believer I had problems with divining for water schemes also. As a mechanical engineer with a master's degree I had problems with divining for water schemes. As a Second Lieutenant Air Force Civil Engineeering Officer I watched the senior civilian plumber on base accurately locate underground pipes with two bent brazing rods....not steel, not two willow stiks or a willow crotch but two bent brazing rods. I pulled his chain about being so old he was there when the dirt that covered those pipes was made so of course he knew where the pipes were. That's when he handed the rods to me and told me to see for myself. Considering my reservations both scientific and biblical I really did not think it would work. It did. I have used bent rods to locate pipes and electric lines since then. Don't ask me how it works, I don't know and I have had enough science to have a pretty good clue about most things. I thought that it might have something to do with magnetism but considering the brazing rods it couldn't be that. Another weird thing is once you locate the pipe you can use one rod to determine the direction of flow in a pipe. I cannot determine depth but only horizontal alignment. I do believe that divining for treasure or to determine the future is not biblical but I am not convinced that finding pipes or electric lines is witchcraft. It is like the difference between astrology and using the signs in the heavens to plant by. The Lord gave us the signs in the heavens as an aide to time keeping and as a calander, read the Hebrew scriptures (AKA Old Testament). I think at some point there will be a rational explanation for the phenomena. I think that the current flow in electric lines may have something to do with it and the water flow in a pipe over time may have an effect on something in the pipe. I have not tried it on PVC pipe so I can't make any correlations between that and steel or cast iron. If your reasons for not using it are not biblical, don't scoff at it, it works. I don't know if works for all people but it has for me.

Eric

seapea · Jul 5, 2005

( Depending on how old your system is, your local health department might have the original plans of file.)

This worked out. Got the approvals for both plans. The old field wasn't located quite where I thought. I figured the line ran out from the septic tank about 70' before the field started, but it's only about 8'. This is actually good news. Should make it easier to place the barn we are considering building.

RobertN · Jul 5, 2005

County probably sent you "As Built" plans? That is what we got for our house. I guess there's the usual building plan, and then As-Built plans showing where things moved for whatever reasons.

Junkman · Jul 6, 2005

( I've never had the tank tested for coliform. I've also never heard of having this done. If it did have coliform, I would assume there is no way to get rid of it. Also, it seems like coliform would readily spread to pretty much ever septic tank in the area via the septic pumping service, unless they sanitize their equipment between each service. )

I was referring to having your water well tested, not the septic tank. If you don't have coliform bacteria in your septic tank, there is a bigger problem than you realize... /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif