New to an aerobic waste system and a question has come up concerning the air being pumped into the system. With the system pumping in air at say 3 CFM on a 24/7 basis, and the lids of the tanks sealed. Where does the air go? The only thing we can figure is any built up pressure would be forced out into the drain filed, but cannot get a definitive answer. Just have this nightmare vision of the lids blowing off like an over heated pressure cooker! Many thanks in advance - GLP

Just curious... what did it cost to get your system installed?

These are batch type treatment plants. 3# pressure is quite low, akin to a beachball. Less than a football. And, it's not 3#X24, it's 3#. Your house water pressure is 50# and it doesn't blow up anything. Remember, your car tires are 32#. Once the cycle is over, the effluent goes to another tank and finally into the leach field. O2 is converted, in part to CO2.

It' not 3# of pressure, it was 3 cfm, which is a measure of volume and not pressure. That would be well over 4,000 cubic feet a day. I would guess that the air goes down the drainline. Isn't there a drainline of some sort in these systems that opens into a leachfield or perhaps even above ground?

Yes, I missed that. It must purge through the leach field. I have worked with some contractors building them for neighborhoods where an individual septic system wouldn't be practical, very hilly areas e.g..

That describes my situation. My leach field is probably a disaster as its 60 years old and there is a flow of water at the base of the field rather frequently. So, this aerobic system interests me. MA, do you have any idea what they cost to install? I have heard that the effluent is so clean, it can be used to water the yard.

The only exposure I have had was in Metro Atlanta in a new neighborhood with remnants of Stone Mountain in the area. They put in a unit to service, If I remember, 60 homes. They cost more to install and operate so I'm not sure about payback. I have an "Infiltrator" system at my GA Mountain home, works great, less cost than stone and line leachfield.

Jlisenbe - Our situation was a difficult one in that we live in a lake home, actually 12 ft off the water, and the old septic system of forty-something years was failing. Because of the numerous large oak trees and the rock/soil, our cost to install a new system was between $12-$15,000. In looking at options, we read where people were selling kits to go in an anaerobic septic systems to introduce air; theoretically converting it to aerobic, at a cost anywhere from $1,000-$1,500. After much reading, searching the net and talking to other folks, we elected to try aerobic using our two existing in-ground anaerobic tanks since primarily they receive only toilet waste as our sinks, showers/tub, washer, etc are run off separate as lawn and garden water. Installed an air pump plumbed to a diffuser in the first tank, which then flows into the second tank, which is now a settling tank. From there it passes through an effluent filter then out to the lateral line field.

According to all we have read, changing over to aerobic process also has the added benefit of cleaning out some of the built up bio mat in the drain field, thus improving drain off. According to what we have found, this is a sixty to ninety day process, so we will see how that works.

All total, we have bought an air pump, fine bubble diffusers, effluent filter and some PVC pipe/fittings/glue. Also we elected to buy two new tank lids with cast in 20-inch risers w/lids rather than fight the issue of cutting holes in our two existing concrete lids and installing raisers/lids. All total we have right at $630.00 into this project. It has only been up and running for a very short time, but so far it appears to be working. Hope this helps.

So you still have to use a leach field?

I guess the true answer to that is “hopefully” we will still be able to use the leach field. We have been told that part of the aerobic process is that the aerobic bacteria will react with the old bio mat in the leach filed and will eventually reduce it, thus allowing continued use of the field for run off. The alternative will be to consider the installation of a chlorinator and move to pumping from the settling tank to the lawn. Not our preference. We would prefer the first option and that is what we are shooting for. As previously mentioned, we are in the very early phase of this and are learning as we go. What we do know is that if you want to do the work yourself, and spend some time shopping for the components and doing a lot of reading, we can accomplish the transition from anaerobic to aerobic for about half the cost of the pre-designed systems currently being offered online.

Just a follow-up on the issue of a retro of an anaerobic septic to aerobic system for those that might be interested. Or problems with our anaerobic septic were much the same as many with older systems. Our system had been set out some 30-40 years ago when our lake home was initially built. The system is a typical twin tank configuration, which is used to primarily address the needs of our toilets (three baths), as our sinks, laundry and showers/tub are drained off for lawn irrigation.

The problems we faced were constant problems getting drainage from the second tank into the leach field. Over the past eight years, we have gone from having the tanks pumped out every other year to the point where we required pumping every six months, and the problems was getting worse. We live on a three quarter acre lot with over ninety trees, most of them large oaks, which slopes from the road down towards the lake. The estimates we had received for a new system ranged in the $12,000-$15,000 range.

After doing some research online, we stumbled across several retro systems for converting to aerobic processing, all noting one of the big effects was to open old drain fields. Obviously we were skeptical, but considering the price of such systems ranging from $1,000-$1,900, we thought it was at least worth the try before committing to new system.

Additionally, after reviewing several systems, we felt that we could purchase the necessary air pump, diffusers/plumbing and design and build our own system. The short story is this; after one month of aerobic operation, our system is processing excellently and we have already seen a marked improvement in the flow rate into the drain field. Our total cost for this conversion was less than $700, which includes not only the pump and diffusers, but also all plumbing, primer/PVC cement and all the little things we added along the way like new tank lids with built-in risers, an effluent filter, values, etc.

Already we can say with a great deal of confidence that if you have an old system that needs attention, a retro from anaerobic to aerobic may just be your answer.