# Septic system questions



## wahoowad (Feb 5, 2010)

Hi folks. I have a drain field as part of my home's septic system (so I'm not on a community/city sewer system). I have a septic tank and pumping tank in my backyard and a pump that pumps uphill to my front yard. My drain field is in my front yard (actually a semi-wooded area that is adjacent to what I consider my yard). You can see long depressions in the ground where my drain runs are located, I assume the ground settled from where these runs were installed about 23 years ago.

I had my septic tank pumped about 5 years ago and the pump replaced (it failed). 

I'm not having any problems, just trying to learn a little bit more. Do the drain field runs need any maintenance? I'm under the impression these are beds of gravel and the waste materials (generally liquid from the overflow tank) are pumped throughout these beds where they dissipate. The ground has settled about 8 to 10 inches along these drain field runs - is it Ok to get some dirt and fill them in to level out that part of the yard?


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## Bobbin (Feb 5, 2010)

The nuts and bolts of the leach field are all below ground, where materials that will faciliate pecolation of waste water were added.  What we see on our leach field (our's is a raised system, too) is just the "skim coat" of soil/loam that allows us to maintain a raised lawn area.  I can't imagine that filling in the depressed areas would compromise the viability of the system.


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## LLigetfa (Feb 5, 2010)

8 to 10 inches is a lot for it to settle.  I would think that the depressions could have a propensity to pool water so I would regrade it to shed water better.  You need a blend of soil that doesn't drain too much.  The water needs to be able to rise through capillary action.  Rather than just fill the depressions with imported soil, I would till it in with what is already there between the fingers.  That will give you a more consistent surface resulting in a more even lawn, assuming you mow the area.  If you don't want to import soil and/or till up the whole area, you could run a plug aerator over the high spots and rake the plugs into the low spots.  Over time the high spots will subside and low spots fill in.

The field was likely made with crushed stone that had paper laid over it and then sand on top of the paper.  The reason for the paper is to keep the sand from filling in the spaces between the stone but if they use sand that is too coarse, it washes down around the stones after the paper disintegrates.


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## Highbeam (Feb 5, 2010)

First thing is that the liquid from your septic tank runs into the drainfield and then down into the ground. It is not meant to come up to the surface. The only thing that you need from the surface is air. The drainfield needs to stay aerobic, plenty of oxygen, to feed the bugs in the field. This is why the maximum bury depth to the top of rock is 24". The depressions above the laterals that you describe are fairly common due to the loose backfill over the trenches settling over time as well as some of the material washing down into the gravel which is not desirable. The best thing that you can do now is to regrade the soil to prevent depressions which will funnel surface water into your drainfield taking even more soil along with it. You must not disturb the gravel or any of the remaining paper/straw/filter fabric/whatever seperating the gravel from the soil above. You would want to remove or destroy the sod layer by tilling and then add and till in a mineral soil that is grey or tan in color as needed to grade the soil level with adequate surface slope to allow water to run past your field. Ideally, you wouldn't even know it's there. The soil you add must not be an organic or clay soil that will retard the passage of oxygen. Course sand is great. 

I have the same problem on my late 60s drainfield made worse by cows walking on it. This spring I'm doing the work described above.


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## semipro (Feb 5, 2010)

I totally agree with the advice offered in prior responses.  I'd also suggest that once you get the field regraded that you maintain a good cover of shallow-rooted vegetation on it such as grass.  The vegetation will help keep the soil active and help to remove excess water.  Remove trees as the roots can invade and clog the drain lines.  Also, try to avoid driving on the area with vehicles as this will prevent further subsidence and soil compaction.


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## LLigetfa (Feb 5, 2010)

Highbeam said:
			
		

> First thing is that the liquid from your septic tank runs into the drainfield and then down into the ground. It is not meant to come up to the surface...


If that were the case, I would be snookered cuz my sand mantle is on top of blue clay.  In fact my field is dug down two feet into the clay and raised three feet above it.  It is designed not to leach to the surface as liquid runoff but rather evaporate up from the surface and through the grass.

Around here a lot of systems are built on bedrock and as such the field won't drain into it either.  Some places are now using large above ground evaporative units with spray nozzles and large foam sponge blocks.


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## LLigetfa (Feb 5, 2010)

Highbeam said:
			
		

> Course sand is great.


When I had my septic field built, the inspector had approved the sand mantle that the licensed contractor used.  I was concerned that the sand was too fine.  We had an overnight rainstorm and there were large puddles of water on the field which I pointed out to the inspector.  His explanation was that the water was supposed to wick up from the bottom and not drain downward.  Sand that is too coarse would drain down and not wick up.  He wanted me to plant grass on it right away so that the vegetation would help draw moisture from the sand mantle.


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## Flatbedford (Feb 5, 2010)

It is also my understanding that the liquid leaves the field through evaporation, not by going down into the soil or bedrock. Maybe give a local septic system guy a call and see what works best for your area.


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## hokiefan (Feb 6, 2010)

If you in va like me most likely you have light sandy soil that will settle like that. I actually planted my garden over my drain field last year[ recycling those nutrients]!!

By the way I'm in southeast va


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## gzecc (Feb 6, 2010)

Hokie, Hope your not going to eat from that garden?


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## Dune (Feb 8, 2010)

The most inportant thing you can do to maintain your leaching feild is to keep fat out of your drains. They fail when fat clogs the sand around the outlets. Pour cooking fat into a can, wipe the pan with paper towels, if you think you spilled grease in the drain, run hot water and detergent down the drain to disperse the grease.

With a commercial grease trap like restaurants are required to have, a septic system would last forever.


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## flyingcow (Feb 11, 2010)

Add onto what Dune said. Also, a pig, or garbage disposal is hard on a septic system. Not good to have one. And i get my tank pumped about every 5yrs or so. If you don't solids will build up and flood the leach field. Or at least thats what should be done up here. i have excellent drainage, but every region is so different in soil composition, some advice may not be applicable in other areas.


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## Highbeam (Feb 11, 2010)

No, the effluent goes down in a standard system. It might go down and then sideways but it goes down first and as it goes down it wets the aerobic soil and the bacteria there provide the secondary treatment. That secondary treatment must occur which is most likely why you, Lligetfa, had to import that sandy soil. In areas of poor soils or high groundwater the imported soil is used to provide that treatment before the effluent hits the groudn water. After the secondary treatment the effluent is "clean" enough to hit the groundwater. Only a small, unavoidable, amount of the effluent wicks up and evaporates. The standard system is designed for more than 300 gallons per day and that isn't going to be evaporating. Gravity is a wonderful thing.

A septic drainfield on bedrock is certainly a challenge. Once the effluent has been properly treated by many of the several new technologies you can actually irrigate with it. You just need to dump it somewhere. 

Don't ask a septic guy, he just follows the designs and plans drawn by an actual engineer. Oh, I'm one of those, a licensed professional engineer. This stuff, poo, is my bread and butter.


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