My septic system's leach field is not able to absorb the liquid that comes out of the septic tank any more. It flows out of the pipes in the leach field and surfaces in the grass. Based on the reading I have done (the "Septic System Owner's Manual" by Lloyd Kahn which is very good) there is a chance of recovering from this problem by installing an aeration system.
An aeration system pumps air into the septic tank, thereby encouraging the development of "aerobic bacteria". The aerobic bacteria need air to survive, and are more voracious eaters than the an-aerobic bacteria that are typically present in a septic tank without air pumped into it. The idea is that the aerobic bacteria will clean up the fluid in the septic tank and then they will also make their way into the lines of the leach field, clearing away the "bio-mat" that has formed over the years. This bio-mat is the thing that is clogging up the leach field, preventing it from doing its job.
Anyway, there are quite a few air pumping systems out there that are designed to be installed into an existing septic system. My question is, does anyone have experience with installing such a pump to deal with this type of problem, and if so how effective was it at clearing up the problem? Is it worth the investment? For some reason these systems seem to cost around $1,000, which seems a lot for what is basically just an electric air pump.
Update: I had the air pump system installed in April 2011, so let's see how it works..! It is an aero-stream unit which sits near my outside electric outlet and there's a plastic tube that is buried a few inches and that goes into the septic system via the outlet riser and down into the liquid. It pumps a lot of air in, the liquid churns around and bubbles continually. So far, I can say that the septic liquid is no longer foul-smelling. It has almost no odor any more. The level of liquid varies, depending on rainfall and water usage. Sometimes it comes to the top of the riser, at other times it's about 10 inches below the top. If this system works, I'm expecting that the level of liquid will fall gradually. This means that the lines are being cleared of gunk. Time will tell… I'll try to report back periodically.
Update June 30 2011
The level of liquid in my tank is about 18 inches below the top now. Very encouraging so far. Mind you, the Spring wet season is behind us, so it could just be due to the water table being lower in the summertime. Also my family was just out for a couple of weeks on vacation which took all the load off the septic.
Update Aug 20 2015
The aeration unit helped a lot but by itself wasn't enough. I ended up digging (by hand) a new "overflow trench" from the tank outlet. I used 3/4" gravel plus a piece of perforated plastic drainage pipe at the bottom. The trench was about 2 foot deep and 30 foot long and ended at a large flower bed which is slightly downhill from the septic tank. With the aeration unit plus this new overflow trench my septic tank is working well enough to not need replacement. The aeration unit ensures that the effluent that sometimes drains into the overflow trench is not foul smelling. This has been working for a few years now. Overflow will happen during periods of high usage such as lots of showering/dishwashing. It's not perfect but it's good enough.
Best Answer
I just had a breakthrough in my situation in the last couple of weeks. My leach field was about 95% clogged, very little if any movement. I had already diverted the graywater to another solution, which helped for awhile, but slowly the field failed to the point of essentially total failure. I have a single septic tank and wanted to try aerating it without the cost of a second tank. I learned a number of things that I haven't seen explicitly explained on any of the forums so I wanted to put it here to hopefully help someone.
I installed my aerator a few months back. Too much air volume and placing it in the center of the tank caused to much churning and cause solids to exit the tank. I did notice the smell though went from putrid to a smell like freshly turned soil (not coincidentally; the same aerobic bacteria live in airy soil). I spent a couple months thinking it didn't work. Water still not going out. But in the last couple of weeks I'm actually seeing the water levels fall to STAY at the edge of the outlet pipe!!!! First time ever!! I used the techniques below to avoid replacing my field without buying a $1000 solution.
You CAN aerate a single tank, but it's imperative that the aeration process doesn't agitate the incoming solids. They have to come into the first baffle and separate so the lighter material can rise and heavier solids fall. To accomplish this you have to use very fine bubbles and they have to be generated as far from the incoming line as possible, or they have to act inside an isolation vessel (there are videos where people use 12" pipe to contain the aerator). You can get diaphragm diffusers for as cheap as $35 if you search around, connected to PVC pipe, and use an air valve to supply JUST ENOUGH air pressure/volume to activate the diaphragm (air RELIEF valve, not cutoff. You'll damage your pump if you restrict airflow inappropriately). Too much and you get a rolling torrent (which you don't want). Place this diaphragm(s) near the output baffle or let it work IN the output baffle. This allows all the agitation to happen away from the settling part of the tank. THIS IS THE KEY, and is the reason why a separate aeration tank is ideal, so there's no chance of agitating the incoming. Also I had a 4" TEE on the outlet side which served as the separator. I put the two diaphragm diffusers on EITHER SIDE of the outlet TEE. You don't want bubbles going up INTO the TEE which could siphon some debris up in there. I got a septic filter brush and put down in the pipe to help filter the effluent, though as clear as the water is going out I don't think it was necessary.
One suggestion I received from a local contractor for my single concrete tank was to empty it, get inside and build a cinderblock wall giving 2/3 incoming/settling, and 1/3 aeration, but the tank has to be pretty good size to do that. You need several hundred gallons of aeration space. I put this on the burner as a next option, but turns out it wasn't necessary.
If you have a way of opening the other end of your leach lines to extend your field, at least temporarily, you get this freshly energized aerated bacteria through there quicker to let it go to work. My temporary relief is now closed off and the field appears to be working!!
Note I did NOT need to buy super duper amped up bacteria to add. From everything I've read this is hogwash and money makers for people. That's like buying weed seeds; give dirt some rain and you'll get the weeds. The bacteria will fill the space if they have oxygen.
My findings confirm for me that the low agitation solutions available out there for $500-$1000 would certainly work. I just chose to play around with a DIY solution.
Hope this helps someone.