how long (in a cesspool) does it take human waste to totally decompose? [new title]

[ralph124c]

..about human waste: how long (in a cesspool) does it take human waste to totally decompose? For example-suppose you stop sending waste into a septic tank-how long till the contents are bacteria-free and harmless?

[SkipMagic]

Wrong cesspool. I'll flush this the way of the other cesspool, GQ.

[VunderBob]

A 10000 gallon septic tank serving a family of 4 is supposed to be pumped out once every two years because the solids build up.

My house that I bought in June has a 10k tank, and the previous owner was a bachelor. In the 20 years he had the place, the tank was never pumped, and he disclosed no history of septic problems. We specifically asked.

[CurtC]

Originally Posted by VunderBob

A 10000 gallon septic tank serving a family of 4 is supposed to be pumped out once every two years because the solids build up.

But that wasn't really the question, right?

[VunderBob]

Originally Posted by CurtC

But that wasn't really the question, right?

Maybe not, but the answer obviously lies somewhere between 2 and 20 years.

In the wild, fecal material lying on the ground doesn't normally last beyond 2-3 months, based on observation of the various kinds of animal crap I find on my property.

[bucknut]

But wasn't the o.p. assuming that a septic tank, if left alone completely, would eventually have its, um, contents decompose to the point that it's sterile?

I don't know if that would actually happen, though I wonder if in the range of thousands of years that would be true. Anyone?

[robby]

Originally Posted by VunderBob

Maybe not, but the answer obviously lies somewhere between 2 and 20 years.

In the wild, fecal material lying on the ground doesn't normally last beyond 2-3 months, based on observation of the various kinds of animal crap I find on my property.

Yes, but the contents of a septic tank aren't exposed to the elements.

I've had the unpleasant experience of taking environmental samples from abandoned septic tanks. (The tanks serviced an old auto body shop, and we suspected the former owner had been been dumping chemicals down the drains.)

One of the tanks had been abandoned 15-20 years prior to our investigation. It still contained raw septage, and was prettty disgusting. (The other tank had been in use up until the day before we sampled it. It was worse.)

[TooTame]

Ok. I have a septic. Mine is a 4bdr. septic, which normally holds more and costs more in taxes hugh! But the septic is never going to decompose. In fact if left long enough it will rot and leak! YUCK!!! Now you can buy some septic stuff kind of what they use in motor homes to help decompose, but really you should get it pumped every two to four years. Also for your houses and your sake....After a while depending on how far the septic is located from your house a stench can arise

[robby]

Originally Posted by TooTame

...After a while depending on how far the septic is located from your house a stench can arise

If you have your septic tank pumped periodically, you should NEVER smell anything. Properly designed septic systems are a safe and effective means of wastewater disposal.

If you do smell foul odors, it's an indication that your system has failed and needs to be repaired or replaced.

[daffyduck]

Originally Posted by ralph124c

..about human waste: how long (in a cesspool) does it take human waste to totally decompose? For example-suppose you stop sending waste into a septic tank-how long till the contents are bacteria-free and harmless?

The contents will never be "bacteria free." Very few places on earth are bacteria free.

Also, septic tanks are not really waste treament systems in the same sense as municipal waste treatment systems are. The real treatment of the liquids happens in the leaching field where it is exposed to aerobic bacteria. The breakdown of solids in the septic tank is really more of a volume reduction process and isn't designed to render those solids safe for the environment. If it did that, you could just pump the septic tank out periodically onto the surface of your property without concern and you certainly can't do that.

I think the key to what you're getting at though has to do with oxygen. As long as the septic tank remains sealed and the environment inside is anerobic, it will be toxic. Waste treatment systems that render human waste safe for the environment rely on aerobic bacteria to do the job.