Septic Systems

[pushkins]

Septic systems are pretty basic in their design and functionality.
The tank holds the liquid and solids allowing the bacteria to eat away at the waste until it is more liquid than solid. The liquid passes out through the leach field pipes and is allowed to soak into the ground.
The soils permeability factor will dictate how fast the "soaking" process takes and usually how long the leach field needs to be.

The biggest reasons for septic failure are tree's/gardens roots etc..., disturbance of the leach field (a truck driving over the pipes and crushing them) and possibly the biggest reason, none biodegradable objects in the tank.

Many septic systems are put on mounds especially where virgin soil is less than ideal for permeability reasons, they build a mound install the tank and then backfill the entire area including trenches with good permeable soil and rock (in the trenches), this allows the leach fields to absorb the waste water into the new soil and help the transition to the original ground.

Systems like this that I've seen fail (only a few) usually come on mounds build over very heavy clay soil and extreme conditions that flood the leach lines , the water cannot soak into the ground fast enough and eventually the water builds up between the new soil and the clay original soil and this is the easiest way out for the water.

So in short contact your health department, get the OK to put in a new system and the area they are allowing it to be installed, then contract with a reputable septic company.

[MomOfToo]

Thank you for responding! The seller's have gotten a few quotes and of course are going with the lowest but they are pretty well known around here. In this state (CT) the health dept has to approve of the area before any work is done. They do the perc testing along with the septic company. All the septic companies that came in to give a quote all say that this area is the best area because it is the driest and has been untouched as well. I am just glad they have to dish out the money for it and not me! I just have to keep my kids toys out the the toilet

[canoebuilder]

yea keep the toys out and as also a good thing is to use T-Paper that does not contain any cotton.
Depending on the size of the tank you've got and the size of your family you also have to have the tank pumped regularly.
I have a 1000 gal. tank for a 3 bedroom house but now there are only 2 living at home and my septic tank pumper told me that I can have it pumped every 5 years but I go only 4 years.
If the solids in the tank can get down into the leaching bed it will cause it to fail.
The only thing going into the bed should be fluids.
Find out from the installer, what his recomendations are for, your size family and tank for a pumping schedual.
Gerry

[MomOfToo]

I was told every 2 years. We are a family of 4, but one is still in diapers lol! We are having them put in a bigger tank (1250) because eventually we want to expand to a 4 bedroom. I have no problem of pumping it every year if I can prolong the life of it. I use Scott tissue now. My uncle who is a drain cleaner always told me to use that kind of toilet paper because its breaks down faster and I mentioned that to the septic inspector and he told me that is fine. I just have to get my son used to throwing those flushable wipes into the garbage can versus the toilet, those don't break down that well even though they say "flushable." Thank you all so much for all the advice. I grew up with sewer/city water. Now I have to deal with well, septic and oil! Ugh-thats what I get for moving to the country I guess!

[LazyPup]

Most local codes determine the size of the septic tank by the number of bedrooms in a house. While most people might think that a bit strange, there really is a good justification for that policy. Consider the facts. Prior to World War II about 40% of all homes in America did not even have indoor plumbing, and of those that did, they generally had one common bathroom for the whole house, regardless of how many bedrooms were present and to this day it is not uncommon in the low priced starter home market to have two, three or even four bedrooms but only one common bathroom. On the other hand, when we consider contemporary custom homes it is common to have a separate bathroom for each bedroom plus an additional bathroom in the basement or perhaps off a mudroom at the rear entrance and perhaps another ½ bath or two. As you can readily see from this, counting the bathrooms does not provide an adequate picture of how many people live in the house or what the average daily effluent discharge might be.

Statistically speaking, when we consider all forms of water usage, cooking, dishwashing, bathing and laundry it has been determined that we produce an average of 200gal of effluent for each adult in the household per day.

The codes are then based upon a statistical maximum occupancy of two adults per bedroom. In order to insure that the tank will have sufficient time for the bacterial digestive process to work the septic tank is then sized to be able to contain a 3day discharge. Example; a one bedroom house would have 2 adults which produce 200gal/day each for a total of 400gal/day. A three day holding capacity would then be 3days x 400gal/day =1200gal.

The size of the leach field is then determined by the absorption rate of the soil at the point of installation. In most regions they still rely upon the “Soil Percolation Test” or commonly the “Perk Test” to determine the size of the leach field. Basically a Perk test is done by auguring three test holes 6 to 12” in diameter and about 3’ deep. The holes are filled with water and they time how long it takes for the water to be absorbed into the soil. From the perk test they then consult a table in the code to determine how many feet of leach field pipe will be required to support the system.

In many regions they no longer use the “Perk test” but rather they are using a “Morphological Soil Analysis”. To perform a Morphological Soil Analysis they use a backhoe to dig 3 holes about 6’ deep then a soil engineer examines the layers and composition of the soil to determine the absorption rate.

Years ago when land was still fairly inexpensive, most counties required a minimum of 2acres for a building lot that was to be served by a septic tank system. Some counties not only required enough land for the septic leach field, they also required a reserve land space large enough to install a new leach field in the event that the existing leach field failed. In those days it was also common for the leach fields to have 3 or 400’ of leach field pipe. As the demand for rural or suburban property increased land prices also increased thus the size of the lots decreased while the average size of the structures placed on the lots increased so they began rethinking the minimum length of the leach fields and in today’s standards a leach field is often a mere fraction of what would have been required as little as 20 years ago.

From this you can easily see that the size of a leach field is totally dependant upon the ability of the soil to absorb water, thus not only can the conditions be totally different from one building lot to another, in some cases such as described in the original post, the conditions may be dramatically different in different areas of the same lot.

HOW DOES A SEPTIC TANK WORK?

In it’s simplest for a septic tank is a water tight containment vessel generally constructed of concrete, although they are now also making them from polyethylene, fiberglass or other water tight materials. The primary tank is divided into two chambers by a set of internal baffles. The raw sewage first enters the “settlement chamber” where the heavy solids quickly sink to the bottom of the tank. It is also in this chamber where the biodegradable solids such as fecal matter break down into liquid slurry. The liquid slurry then passes through the baffles into the digestion chamber where “Anaerobic bacteria” (Bacteria which thrive in the absence of oxygen) basically eat the slurry. During this process the slurry is converted to “Gray water”, which then passes into the leach field.

Although it is very slight, none the less, some atmospheric oxygen does penetrate the soil and gets into the leach field pipe, thus there is aerobic bacteria (Bacteria which require oxygen) in the leach field that complete the digestive process. As the aerobic bacteria complete the process they basically convert all the remaining biodegradable material into various forms of nitrates, carbon dioxide and water. The codes then require that we keep a good ground cover of sod over the leach field because the grass roots absorb the nitrates and carbon dioxide as nutrients and the remaining discharge is pure water.

A BUNKER SYSTEM

In some coastal or wetlands areas were the soil will not an absorption test sufficient to permit a conventional septic tank system in order to build on the lot many localities now permit an above ground bunker system.

To build a bunker system they first layout a rectangular plot large enough for the septic tank and leach field. Around the perimeter of the plot they construct a 4’ high retaining wall of concrete blocks or railroad ties. The septic tank is then set inside the retaining wall on the end closest to the structure with the discharge port of the septic tank positioned about 4’ above grade. The enclosure is then filled with sand until it is level with the underside of the septic tank discharge port and the leach field lines are laid on top of the sand. Additional sand is then added until all four sides of the enclosure are pitched upwards toward the center at about a 30degree angle. The sand is then topped with a layer of topsoil and sod is laid to cover the entire structure. There are two downsides to this type of system. 1. Not many people would want a 40x 100foot bunker erected in their back yard and 2. If the sod covering is not properly maintained the sand will quickly erode and expose the leach field.


AERATED SEPTIC SYSTEMS

They are now making an aerated septic system, which lends very well to areas with confined space or where the soil will not pass an absorption test. In an aerated system they begin with a conventional septic tank but in place of a leach field they install a third tank chamber. Inside the third chamber there are airlines in the bottom of the tank that have special nozzles to discharge air into the tank. The air is supplied from a small electrically operated compressor in the house. The air nozzles and compressor have to be carefully designed so that it will supply an adequate supply of oxygen to support the aerobic bacteria that would normally be in a leach field, while not enough air as to cause unnecessary agitation in the tank. With the inclusion of an aerated chamber the liquid discharged from the tank is pure water and may be discharged directly into a storm drain or other surface watershed.

Some jurisdictions also require a chlorinator be installed on an aerobic tank system. The chlorinator is simply a vertical piece of 3” PVC pipe teed into the discharge line with a common threaded cleanout cap installed on the top of the riser. The homeowner must then open the cap periodically and drop in large chlorine tablets similar to the puck type chlorine used in swimming pools.

PUMPING SEPTIC TANKS
It seems that every time someone mentions septic tank maintenance everyone chimes in that the tank must be pumped every 2 or 3 years. Personally I fail to see any justification for that other than to keep the guy on the pump truck busy. The necessity to pump a septic tank is based solely upon the rate at which non-biodegradable solids such as used condoms, feminine hygiene products and those stupid plastic disposable toilet brushes build up in the tank. If I could impart no other advice in regards to septic tank maintenance let me offer this. With the singular exception of toilet tissue, nothing should be put into a toilet unless you either ate it or drank it first.

Now I am sure that many will argue with me on this but in my region pumping a septic tank is almost unheard of, except when abandoning a tank. When abandoning a tank we are required to pump the tank, then punch a 12’ diameter hole through the bottom of the tank and the top must be collapsed into the tank, then the remaining hole is filled with sand and covered with topsoil.

In 1961 I helped my granddad install a septic tank on the family farm. Granddad passed away in 1965 and my uncle took over the farm until he had to give up farming for health reasons and sold the farm in 1989. Last December, out of curiosity I went back to see the old farmstead, and while talking to the new owner he asked me if I knew where the septic tank was? He said he had no problem with it, but they did have to snake the line from the house to the septic tank and found it was about 100 feet, although he had no clue in which direction.

[crabjoe]

Originally Posted by LazyPup

PUMPING SEPTIC TANKS
It seems that every time someone mentions septic tank maintenance everyone chimes in that the tank must be pumped every 2 or 3 years. Personally I fail to see any justification for that other than to keep the guy on the pump truck busy.

I have to agree with you 100% on this. Most everyone I know has never had their tank pump. The few I know, that do, do so because someone told them it needed to be done every few years. I've got one neighbor that gets their tank pumped every year and I've got friend that have been on septic for over 20+ years and never pumped. None have had problems with their septic.