Are you sure about that?
A septic tank is an alternative to a public sewer connection, usually used in rural areas that don't have public sewers. It's designed to basically anaerobically (or sometimes aerobically) digest waste and rot it down and return the waste water to the environment in a 'reasonably' clean state.
I've never, ever heard of them being used in urban sewage as you'd most likely massively contaminate the ground water. They work fine in very low density population areas but if you've lots of them clustered together, you really need centralised sewage treatment as otherwise you're relying on everyone maintaining their systems perfectly and in the real world that won't happen.
You can also do much more high tech treatment in a big centralised plant due to the economies of scale involved.
In rural areas, if one tank goes wrong the dilution factor (i.e. not having very many homes) will usually (but not always) mitigate that to some degree.
It wouldn't really make any sense to have a septic tank and a public sewer.
In a public sewage system you're taking waste from homes and businesses and treating it centrally (usually to a much higher level of purity than a septic can could possibly do) and then retuning the cleaned water to the environment.
Explains all : http://en.wikipedia.org/wiki/Septic_tank
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Kenmore89 and Laundress:
The types of chemicals in drain cleaners are probably falling foul of increased consumer protection and environmental safety and even safety at work legislation.
Pouring harsh chemicals down a drain could damage the drain if you don't know what kinds of materials are involved. Most of us are blissfully unaware of what our drain pipes are made of unless we were involved in specifying the installation (built the house ourself) or we've had a problem and had to figure out what they're made of.
Most of us buy a house, and the drains, toilets etc are already in place and we've little/no idea how they all work beyond maybe the house plumbing and fittings. Once it goes down the drain, it's into buried pipes that could be decades or even centuries old.
Some caustic solutions may react very badly with old cast iron, steel and concrete drains and could dissolve the surfaces, cause pitting etc.
A lot of the older Victorian era (19th century) sewers around here would be made from wide cast iron pipes. They'd never use that kind of material these days as it would be astronomically expensive compared to plastics and concrete.
From a Health and Safety / Safety at Work point of view, you're possibly pouring nasty chemicals into a pipe that could subsequently be opened by a sanitation worker or a plumber needing to unblock it.
And, as Laundress pointed out, there's a risk of a violent reaction in a sink trap which could blow up in your face (literally).
There are also considerable issues with using liquid chemical drain unblockers or large amount of chlorine bleach or strong chemicals in general in septic tanks as you can kill off the bacteria that breaks down the sewage and cause major environmental contamination of ground water.
If you completely sterilise the septic tank, it will just sit full of gunk and you might need to actually add bacteria in powder/liquid form to re-colinise the tank.
In those kinds of systems, non-biodegradable material will also end up back in the environment so you should probably avoid pouring anything that isn't going to break down by biological action / reaction with water over time into your drains.
Even urban sewage plants don't really appreciate people putting in non-biodegradable products as they can ultimately pass through the plant and into the environment.[this post was last edited: 1/20/2015-07:44]
A septic tank is an alternative to a public sewer connection, usually used in rural areas that don't have public sewers. It's designed to basically anaerobically (or sometimes aerobically) digest waste and rot it down and return the waste water to the environment in a 'reasonably' clean state.
I've never, ever heard of them being used in urban sewage as you'd most likely massively contaminate the ground water. They work fine in very low density population areas but if you've lots of them clustered together, you really need centralised sewage treatment as otherwise you're relying on everyone maintaining their systems perfectly and in the real world that won't happen.
You can also do much more high tech treatment in a big centralised plant due to the economies of scale involved.
In rural areas, if one tank goes wrong the dilution factor (i.e. not having very many homes) will usually (but not always) mitigate that to some degree.
It wouldn't really make any sense to have a septic tank and a public sewer.
In a public sewage system you're taking waste from homes and businesses and treating it centrally (usually to a much higher level of purity than a septic can could possibly do) and then retuning the cleaned water to the environment.
Explains all : http://en.wikipedia.org/wiki/Septic_tank
---
Kenmore89 and Laundress:
The types of chemicals in drain cleaners are probably falling foul of increased consumer protection and environmental safety and even safety at work legislation.
Pouring harsh chemicals down a drain could damage the drain if you don't know what kinds of materials are involved. Most of us are blissfully unaware of what our drain pipes are made of unless we were involved in specifying the installation (built the house ourself) or we've had a problem and had to figure out what they're made of.
Most of us buy a house, and the drains, toilets etc are already in place and we've little/no idea how they all work beyond maybe the house plumbing and fittings. Once it goes down the drain, it's into buried pipes that could be decades or even centuries old.
Some caustic solutions may react very badly with old cast iron, steel and concrete drains and could dissolve the surfaces, cause pitting etc.
A lot of the older Victorian era (19th century) sewers around here would be made from wide cast iron pipes. They'd never use that kind of material these days as it would be astronomically expensive compared to plastics and concrete.
From a Health and Safety / Safety at Work point of view, you're possibly pouring nasty chemicals into a pipe that could subsequently be opened by a sanitation worker or a plumber needing to unblock it.
And, as Laundress pointed out, there's a risk of a violent reaction in a sink trap which could blow up in your face (literally).
There are also considerable issues with using liquid chemical drain unblockers or large amount of chlorine bleach or strong chemicals in general in septic tanks as you can kill off the bacteria that breaks down the sewage and cause major environmental contamination of ground water.
If you completely sterilise the septic tank, it will just sit full of gunk and you might need to actually add bacteria in powder/liquid form to re-colinise the tank.
In those kinds of systems, non-biodegradable material will also end up back in the environment so you should probably avoid pouring anything that isn't going to break down by biological action / reaction with water over time into your drains.
Even urban sewage plants don't really appreciate people putting in non-biodegradable products as they can ultimately pass through the plant and into the environment.[this post was last edited: 1/20/2015-07:44]