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Another Septic system question

Old 07-16-2007, 02:01 PM
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Default Another Septic system question

When my house was built they did not put enough top soil over the septic tank (maybe 2-3 inches) so when the weather gets hot, I have a nice and perfect rectangle of dried grass (4'x5') over the tank. No problems with the system, it's just that the concrete tank absorbs the water and the grass dies above it. I can't add more top soil because it will raise the grade and will be too noticeable.

The only solution which comes to mind is to dig up the soil and coat the top of the concrete tank with one of those basement waterproofing finishes. I figure this will stop the concrete from absorbing the moisture


Any suggestions?
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Old 07-16-2007, 02:11 PM
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Default Re: Another Septic system question

Mine does the same thing. I always thought that there wasn't enough dirt to support a good root system for the grass so when it gets hot and dry the grass doesn't stand a chance. Never thought that the tank was absorbing the water. Does this mean that the liquids in the tank are also leaking out through the sides and bottom before and/or after the bacteria digests it?

I pay attention to these septic threads because I had a total system failure 1 year after I bought this $hit box on the lake.
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Old 07-16-2007, 02:16 PM
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Before I went to the trouble to clean it and paint it I would try a plastic barrier of some sort. BUT....... I don't think that is your problem. Basically speaking, the shallower root zone in that spot is limiting the amount of water that can be stored, thereby causing the turf to wilt. The only thing that I think will help is more frequent irrigation in that area. If you could give it a little shot of water on the hottest days, you'll see some recovery.

Next summer, keep it wet before it has a chance to bake. It's much easier to keep living grass alive than it is to bring it back from the dead.
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Old 07-16-2007, 02:20 PM
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Default Re: Another Septic system question

I don't know much about septic systems but I believe the walls of the tank are thick enough so that there is zero leaching out. But they will absorb moisture like a sponge... If I keep one of the irrigation system sprinkler heads on this spot the problem will go away so that strikes down the theory of not having enough soil for the roots... I need to find a permanent solution to stop the concrete from absorbing all the moisture. Also, I talked to my septic guys and they said it's a common problem and has nothing to do with the health of your septic system.
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Old 07-16-2007, 02:39 PM
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Is it possible that your waste is of a particulary acute stinkage and that is killing the grass?

I think I made up a word....hey, that feels good...kinda like Webster over here...just kidding firefly....
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Old 07-16-2007, 02:42 PM
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Default Re: Another Septic system question

I'm cornfused... The septic tanks around here have holes in the sides and no bottom...
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Old 07-16-2007, 02:57 PM
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Joe,
Don't waste your time. There is not enough soil to hold moisture. Picture it as a piece of ledge under your lawn. It heats up and cooks the roots of the lawn.

If you really can't raise the grade you can try and add some clay under the loam but my guess is that it too will be a loosing battle.

I'm sure there is a way to raise the grade over the tank with maybe a fancy hump covered with flowers or ground cover.

Rob
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Old 07-16-2007, 03:00 PM
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I am by no means an expert but I believe the tank fills and is then drained into the leach field. Regardless, the top does not have holes in it and is absorbing the moisture from my lawn and drying it out, leaving a yellow 4'x5' rectangle.

Onejacker, we don't use the toilets in the house - everyone who visits the house uses the tropicana piss can and throws it in the woods j/k
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Old 07-16-2007, 03:04 PM
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Our tanks have 4 sides and a bottom and then there is a concrete slab used for a lid. As the waste breaks down into an effleunt, it exits out the output into a distribution box such that each leg of the drain field gets an equal distribution of $hitty liquid.

I still don't think the tank is robbing the soil of water. Like OriginalSin, the root system of this patch of grass is not large enough to store water in its roots to weather drought like the grass that is not covering the tank. I think that if you waterproof the lid that you will still have the same problem with the grass.

When you say the walls on the tank will absorb water but are too thick to let it leach out, what do mean? Can water/liquid only flow through concrete in 1 direction or are you saying the tank walls are thicker than the lid?
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Old 07-16-2007, 03:05 PM
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Thanks Rob. We have a fairly large flower bed around the house and the roses have crept over the border and onto the lawn in that vicinity. I guess now might be a good time to make the beds larger (mulch over the septic tank) and allow the roses to do their thing.

The ledge explanation explains what's going on over on the back perimeter of my lawn. It just never grows back there and it's in the sun all day. I've suspected ledge all along... They blasted the $hite out of everything to get the house in on top of the hill and pretty much everything up here is ledge.
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Old 07-16-2007, 03:07 PM
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Hardlivin- I have no clue what it looks like and was making (up) assumptions. I don't know how a septic system works and don't know what one looks like other than there is a tank and a leach field. Probably just as you described.
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Old 07-16-2007, 03:12 PM
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The concrete tank isn't absorbing water, at least not enough to kill grass, you just don't have enough dirt on top to support the root structure of the grass and the shallowness allows the moisture to evaporate from the soil. Very common over septic tanks. Add a few inches of topsoil and seed or sod over it. Coating the tank would be a waste of time.

Quick lesson on how a septic system works. The tank retains solids, liquid flows out into the leachfield/drain field/absorption lines etc. and permeates out into the soil. Soil texture determines how fast water will permeate through soil, so a heavier clay soil will require much more leachfield than a sandy soil. Oxygen is present in soil, so an aerobic bacteria builds up in the soil to break down the wastewater. You should pump your tank out periodically to keep solids from building up so much in the tank that they start going out into the leachfield. This will cause the leachfield to malfunction, although a leachfield will "die" sooner or later.
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Old 07-16-2007, 03:16 PM
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Man, I wouldn't worry about it. How long would it take a material amount of water to pass through a concrete lid and go into a septic tank anyway? Unless your tank is damaged or the lid doesn't completely cover the tank you're in good shape. I would think that double or triple flush that is required on the new low flow toilets is doing you more damage than water leaking through concrete.

I would be more worried about my leach field if the ground is all ledge (if ledge is rock).
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Old 07-16-2007, 03:37 PM
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Hardlivin- I wasn't worried about water getting into the system via the top/cover, I was worried about my grass dying above it and wanted to prevent this from happening.

Pug- great write up on how they work. Knock on wood but mine seems to be working pretty good these days. It's a 4 bedroom system and only 2 of us live in the house so it does not get heavy use. I just hope it lasts for many years!
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Old 07-16-2007, 03:44 PM
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Default Re: Another Septic system question

FireFly - 7/16/2007 3:37 PM

Pug- great write up on how they work. Knock on wood but mine seems to be working pretty good these days. It's a 4 bedroom system and only 2 of us live in the house so it does not get heavy use. I just hope it lasts for many years!
The two most common signs that your system is malfunctioning are:

1. Excessive moisture or standing/stinking water in the area of the leachfield. This means that the soil can't absorb any more water either because you're using too much or rain is saturating the ground.

2. Slow flushing/Standing water around the tank. This usually means that the pipe heading out to the leachfield is clogged and all the water is stacking up in the tank. It will usually surface around the tank and cause slow flushes. It may back up into the house, but rarely.
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Old 07-16-2007, 03:46 PM
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Oh, not the way I read it. I've got the same problem but as long as I irrigate it is not noticeable. Post up if you come up with solution.
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Old 07-17-2007, 10:28 AM
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FireFly - 7/16/2007 2:20 P
If I keep one of the irrigation system sprinkler heads on this spot the problem will go away so that strikes down the theory of not having enough soil for the roots... I need to find a permanent solution to stop the concrete from absorbing all the moisture.
It's not about the amount of soil for the roots, it's all about how much water that soil can hold.

Imagine all of the pore space between the particles of sand/silt/clay in the soil over the tank. Now imagine that collective amount of pore space as a bucket that you store irrigation water in. There is a limited amount of soil in the area in question, which limits the amount of capillary pore space (aka macro-pores), which limits the amount of water that the soil in question is capable of storing for your grass to use.

Make sense? It should. I have a degree in Agronomy from NCSU that required countless hours of Soil Science. Soil Science is all about soil composition, nutrient holding capacity (aka Cation Exchange Capacity), and soil hydrology (which is what explains why your grass is dying).


Mis-Rest had a great idea, btw. If you can till a clay into the existing soil, you will greatly increase the water holding capacity if that soil. I think you'll find that this will go a long way to solving your problem.


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Old 07-17-2007, 12:28 PM
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Another solution for you would be a granular wetting agent.

At some point in the past a soil scientist figured out that the surfactants used in laundry detergents to reduce surface tension in water could be used in the agricultural industry to make irrigation water more efficient. The reasearch of this topic led to the development of several different types of products ranging from penetrants that flush water through the soil to omni-directional products that increase water holding capacity of soil.

Find out where your local golf course superintendents buy their products for their courses. Ask the salesman behind the counter what he has available in a granular wetting agent. Follow the directions on the bag and apply the product to the area in question. This will have a similar effect to the recomendation above about tilling in clay, but this can be done over the top of the existing turf instead of having to remove the turf and till, re-sodding or re-seeding afterwards.
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Old 07-17-2007, 04:05 PM
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Default Re: Another Septic system question

Afishinado - 7/16/2007 2:42 PM I'm cornfused... The septic tanks around here have holes in the sides and no bottom...
I had to do a little research, but I just learned I have a cesspool not a septic tank
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Old 07-17-2007, 04:19 PM
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Here in La. where the water table is only a couple feet below ground level, a filter bed, or cesspool won't work. The ground is very close to saturated all the time year round.

We use a sewer treatment plant, on a smaller scale but pretty much the same design as a municipal treatment system. Solid removal, aeration, and sanitizing.

As much as I hate to admit it pugg man is right. The concrete tank is not absorbing water. The soil is thin over the tank so the sun dries it out. That's why irrigation helps.

Not bragging but I have a level II waste water treatment and collection certification. I am licensed to work in a treatment plant in a town with 10,000 people or less. My wife calls it a degree in "Turd Chopping". I get no respect.
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