How It Works

First off.  Why do we even need septic systems?  Or as we call them, Onsite Waste Water Management Systems.  Why can’t we just plumb a pipe into the nearest stream, lake, or river?  Or just simply plumb the waste to a road ditch?  These are very good questions I get asked more often than you think.

Most people care about their neighbors, their well water, the environment.  But when sewage starts to get out, and it’s going to cost money to fix it, these questions come up.  For example, “Is it okay to release in the back field, as no one lives back there anyways.”  Whew, that one is asked so often, if I had a nickel for every time i was asked, I would be rich.  As you read this section, I hope you get a better understanding of why we need to control our “Waste Water” onsite.  And everyone has the right to know that their neighbor, up the road or hill, is doing it right, and not contaminating their well water.  Believe me, there are nightmare stories about sewage in well water in every health department in the U.S. and it’s a growing concern.


What does Septic Mean?  It means that the environment in the septic tank is void of all oxygen.  Or it’s gone septic.  Why is this important?  Well, we have to remember why we are treating wastewater.  There are three important types of bacteria in wastewater we must destroy before releasing into the environment.

1. Aerobic Bacteria and Pathogens:  Need oxygen to survive

2. Anaerobic Bacteria and Pathogens:  Need absence of oxygen to survive

3. Facultative Bacteria and Pathogens:  These are harder to destroy, because they don’t care if there’s oxygen or not.

Now how do we treat all three.  Well.

1. Aerobic Bacteria and Pathogens:  The septic tank is the best place to destroy these.  See being a septic tank, if you took a dissolved oxygen measurement out of the wastewater, it would read zero.  That’s right, there will be no dissolved oxygen in that water.  So the Aerobic Bacteria perish here.  But let’s not forget the other reason we need a septic tank. It’s to separate liquid from solids and only allow liquids to enter the drainfield.  If you allow your septic tank to get too full, it will lose that ability and will send solids out to the drainfield, essentially plugging it up and needing replacement.  (Now I have been asked this)  If the septic tank is leaking out the bottom why is it that it needs repair.  What’s the difference if the sewage gets out of the septic tank or the drainfield.  Please remember, the sewage needs 72 hours of septic tank treatment for clarification and to kill aerobic bacteria found in human wastewater.  If we simply flush the water down to a leaking tank, it’s going to head straight down to ground water without adequate anearobic, anaerobic, or facultative treatment.  We cannot skip any one of these steps as we can hurt our environment and make others very sick. Oh, and possibly contaminate your very own well water.

2. Anaerobic Bacteria and Pathogens:  These don’t like oxygen and will die in the presence of oxygen.  In a traditional septic system’s drainfield.  It is the drainrock that was installed that they die here.  Pretty much as soon as they hit the drainrock.  Now beneath the drainrock there is soil, but that’s the next and final step.

3.  Facultative Bacteria and Pathogens:  These don’t care about oxygen at all.  They will survive either way.  But through plain old friction alone, in the soil beneath the drainrock, they get hung up.  And die.  All within six inches of leaving the drainrock.

Pretty cool stuff huh?

Waste enters the tank from the left side of the picture.  This inlet pipe is called a baffle.  The inlet baffle’s funtion is to keep the tank quiet.  The bacteria that makes a septic tank work does not like agitation, and must be left still.  So the waste exits the inlet baffle through the bottom into the effluent Layer.  (Effluent by definition is water that has been treated by a septic tank.  It isn’t fully treated yet, don’t be fooled.)  Solids will float to the surface forming the scum layer, or the solids you see when you open the lid on your tank.  Bacteria goes to work right away on the solids breaking it down into sludge.  That is what forms on the bottom of the tank.  It is a thick black goo.  Really gross.

As waste is entered into the septic tank, effluent is displaced out the outlet baffle.  The outlet baffles funtion is to keep the solids from continuing on.  If solids were to get out, it would plug up pumps and drainfield, depending on your system. Either way it is vital in your sewage treatment facility.  You may also have an effluent filter in your outlet baffle.  It filters down to 1/16th of an inch.  An extra addage to be sure solids don’t enter your drainfield, or pumps.

For even further details on how it works, click here.

Now the above is the most basic of septic systems.  There are much more complex systems and you want to be sure the technician you call out has the certifications for your system.  Below I put a link from the University of Minnesota.  I have spent extensive hours training with David Gustufson, and I have his permission to put his link on here.  He explains your Aerobic Treatment Unit (ATU) best.

Below is a link about Recirculating Media Filters.  These are top of the line for removing nitrates in our waste.  In case you were wondering Nitrates are poisonous to children and many have died before the advent of septic systems.  Thanks to our greater understanding of how septic systems work, and continuing education to make them better, we have not had a nitrate death in over 80 year.

Now if you have a sand mound filter, you have a huge Mound, in your yard.  Please resist the urge to level it.  It needs the slope integrity to work.  Most of your wastewater treatment is through evaporation, and not through ground absorption.  Sand mounds can get soggy if they are overloaded, or if a pump is not set up correctly and is sending out too much effluent, “dirty water,” to the sand mound.  You may have to replace an on/off switch, replace a pump, or reset some timers, now it’s highly unusual that it’s all these things, it’s usually just one of them.

You may have a sand filter.  There are sand filters with a pump inside and there are sand filters with no pumps.  Then the effluent is either discharged out through the bottom of the sand filter to a drainfield, or pumped out.  Depending on grade and if the drainfield is a gravity drainfield or pressurized drainfield.  You could have a sand filter and a sand mound on the same property.  Depending on how your soil can treat wastewater.  A soggy sand filter is usually nothing to get too excited about, but it does need corrected soon.  See, a sand filter is an aerobic environment, the bacteria there need oxygen.  If it goes under water, they will drown and cause all kinds of issues.  During our maintenance checks we also check the pumps and alarms if applicable to let you know that a problem maybe developing in those areas.

Septic Systems on Timed Control Dosing.


Today, I got a call from a nice lady confused of why she needed a septic inspection when it was only a year old.  I can totally understand the why.  She paid over 15,000 dollars for this septic system, why does it need inspected all ready.  She stated that it was a basic septic system, and doesn’t know what all the fuss was about.  I told her it’s a real good idea to have your septic system inspected periodically to be sure it is functioning as designed.

She scheduled, and I came out.  I came out to find a pretty complicated septic system.  There is a computer running the whole show, and someone had opened it up and messed with the timers.

Septic System Contol Panel

Septic System Control Panel

Here is a control panel for a septic pump.  It is controlling the on/off time of the pump.  Now at this location, this septic system was engineered to time-dose a sand filter only 20 gallons of effluent every 1 hr and 45 minutes.  And it is to run this setting forever.  Now you may ask, “how do you know how much water is being pumped, there’s no flow gauge or flow meter inline?”  Now this is where things get a bit tricky.

First you must find the volume of the pump tank.  LxWxH.  That is your volume in cubic feet.  In this tank we were 3 feet x 6 feet x 4 feet.   That is 72 cubic feet.  Now we need to convert cubic feet to gallons.  There is 7.48 gallons per cubic foot.  So we multiply the two.   That gives us 538 gallons.  Now, we need to figure out the gallons per inch.  The tank is 4 feet deep, so we divide 538 by 48 inches.  That gives us our gallons/inch.   About 11 gallons of water per inch.

Now we can see how much the pump is pumping.  I took a depth measurement of the water in the tank.  Then turned the pump on for exactly one minute.  I need to know what this pump is pumping per minute.  I got 5 inches of drawdown in one minute.  At 11 gallons per inch, we are pumping 55 gallons per minute.  The pump is doing great and the sandfilter is accepting water at an acceptable level.

Now here’s where the problem is.  I found the on-time for the septic pump at 1 minute 45 seconds on.  That’s over 90 gallons per dose.  This is over the maximum by nearly 4 times the acceptable level.  This now explained to me, and the homeowner why the sandfilter was so soggy.  It was getting slammed too hard all at once.  Remember this septic system was designed to have 20 gallons per dose.  This system was heading down the road to failure quickly.  And it was only a year old.

Here’s a picture of the septic system with the lids opened.

The lid closest to me is the solids handling tank.  It was nearly empty. One inch of scum and zero sludge.  Second compartment is the clarifying chamber.  It was also empty with zero sludge and zero scum.  But there is a filter in this one that needs cleaned.  I will show a picture of that in a second.

The furtherest lid is the pump compartment.  It’s designed to be a surge tank and gather enough effluent to push it out to the sandfilter. But only time dosing it 20 gallons every hour and 45 minutes.

The first two compartment of this septic tank are what normally needs pumped.  About every 5 years if used properly.  If one person lived on this system, it could easily be 15 years between septic pumpings.   A family of 9 or more would be pumping this more frequently.  Sometimes every 2-3 years.  Remember, this system will only handle what it was designed to process.  In this example, it is designed to handle 360 gallons of wastewater per day.  And yes, showers, baths, laundry, and cleaning is included in this amount.  With a system like this one, if you exceed the amount, an alarm will go off asking you to back off until it can catch up.

Part of the inspection I check to make sure all alarms are functioning.  We want to make sure it will tell you that something is wrong.  There is a silent switch on all alarms.  Let me assure you that this doesn’t mean you fixed it.  It means you acknowledge the alarm and are doing something to fix it.

Here is the septic filter I was talking about earlier.  I am taking the picture after it was cleaned, so you aren’t seeing it all goopy and stuff sluffing off of it.  It’s not too pleasant, but it’s job is vital on how long this system can function.

There was one homeowner that was tired of cleaning it yearly, so he threw it away.  Well the filter is designed to trap particles from going into the sand filter and plugging it up.  And yes he plugged up his sandfilter in 5 years, and needed to be replaced.  Another $5,000 – $7,000 dollars for a new sand filter.  Seems like I’d keep it in and keep it clean.

I really hope you are getting a lot of information from this site,  If you are, please leave me a note.

Septic Sand Filters:

Okay, if you have one of these, you maybe wondering why, and how it works.

First thing, is why do I have a Sand Filter?  That one isn’t so easy for me to answer.  It could be that you have a small lot, and you need a form of septic pre-treatment before releasing to your drainfield.  It could also mean that the ground you live at is absorbing water too quickly and not performing septic treatment before being released into ground water.  eww, remember that’s where our drinking water comes from.  Or you could have high strength waste that needs further treatment to bring it’s strength down to residential waste strength.

It is really hard to see this sand filter.  But the lush growth in the grass is it.   And the open green whole is where the septic pump is housed.  Geographically the wastewater gets to the sand filter via a pump just after the septic tanks.  There are five distribution lines on this sand filter that extends the entire surface of the sandfilter.  The lines are located just beneath the soil.  At the end of the sand filter there are flush-ports.  It is not necessary to have these installed but it is a really good idea.

If  the flush ports are installed I can flush the sand filter lines every year at inspection time.  Extending sand filter, and septic pump life.  Remember, the pumps job is not to just move water from one place to another, but charge all the lines in the sandfilter, and clean the lines with water volume and pressure.

If the pump is cleaning the lines all year, where does the gunk go that it’s cleaning.  Well, to the end of the sandfilter lines, plugging it up in slow motion.  Usually about 10 years after the sandfilter is installed, if not flushed, the lines will need jetted.  Jetting is expensive and could easily be avoided if the septic sand filter was flushed out yearly.

Septic Sand Filter Flushing Port

Here is the septic sand filter’s flushing point.  And if you look closely, a little frog is in the pipe.  He came and surprised me as I was working.  I worked around him and left him to his home.

Anyhow, I uncap the pipe and turn the pump in the pump tank.  Not the sand filter.  It ejects any build up in the pipe out.  And keeps it clean.  The build up is usually not a septic tank going too long between pumpings.  It is normally bacteria growth forming in the lines.  This is what get cleaned out everytime the pump comes on.  And builds up at this point.  If allowed to go too long it will plug up cause a pump to burn up in the pump tank.

Pressurized Drainfields

There are two types of drainfields.  The one I am going to show now is pressurized drainfields.  The other one is called Gravity Drainfields.

What makes your drainfield pressurized?  Usually it means there is a pump before your drainfield,  But now there are those drainfields that are high up on a hill somewhere, and you need to push water to it, but it can still be gravity.  Just ask, and I find out.

Okay, why pressurized over gravity.  I am a fan of pressurized septic drainfields, because it’s a more efficient way of treating wastewater.  Usually there are three or four trenches, dug into the ground, and a long black dome is placed on top of all the trenches.  There is a long pvc pipe over the entire trench, and holes drilled in this pipe every three inches.  This way the pump charges the drainfield lines, and squirts the top of the black plastic domes.  Then the mist of water lays down on the bottom of the trench evenly.  Over the entire surface of the drainfield.  These  are much easier to take care of, and if proper maintenance is performed, will last much longer.

All pressurized drainfields should have flushing and monitoring ports installed.

Septic Pressurized Drainfield Monitoring Port

Septic Pressurized Drainfield Monitoring Port

Here is a monitoring port on a septic’s pressurized drainfield. Now you can ask, what is it telling me.   There are three monitoring ports on this drainfield, and a squirt test must be performed.  This is to make sure that the entire drainfield is taking the wastewater equally.  If I turn on the pumps and the 3 monitoring ports squirt up water at the same level, then it is working equally.  If we were to get one that was squirting 6 inches, and the other two are squirting 5 feet, then there’s a problem.

One line of the three is working less than the other two.  This will cause the other two to treat more wastewater then they were designed for and will cause that drainfield to lose years of life, causing a premature failure.

It is a simple adjustment to get them back to equal, there is a valve at the headworks that needs a minor adjustment.

I didn’t need to dig it up on this site, as all lines were equal.  I will post one as it comes available.

Septic Pressurized Drainfield’s Flush Port

Below is the flushing port to the septic pressurized drainfield.  Now the pump that feeds this drainfield has two jobs.  It needs to move water from one location to the drainfield, but at a sufficient volume and pressure to clean the lines.

Septic Pressurized Drainfield Flush Port

Septic Pressurized Drainfield Flush Port

Now when the pump comes on, it keeps the lines in the drainfield clean.  When it cleans it sends all the gunk to this flush port to be collected prior to flushing.  If we don’t flush the drainfield, it will clog the drainfield, and can cause premature pump failure.

Also if the pump starts pumping at an unacceptable rate, and starts drooling the water into the drainfield, then the water will not clean the lines.  Some may call this scouring of the lines.  They both mean the same thing.  This is why we always test the pump, to make sure it is working good enough to keep the lines clean.  If not, then we replace it before it plugs something up.

Now, I simply remove the cap and manually turn the pumps on, and eject the build-up out of the septic’s pressurized drainfield.

I flushout the remaining drainfield lines and now I am done flushing the drainfield.


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