In the sailing community more and more people are using composting toilets: https://farmingmybackyard.com/diy-composting-toilet/
As long as it is disposed of safely (properly composted), the cost here is the composting material.
Every few decades for a properly sized and properly functioning system.
That sounds about right if the goal is to keep a system that's not properly functioning (not enough microbes to break down solids) from filling up to the point of causing problems. You won't go wrong if you follow that advice but depending on what goes into your septic (do you have a garbage disposal, do you do laundry with bleach, number of people in household, etc) you may be able to go an order of magnitude longer. Recommending a system be pumped every 3-4yr is like a 3k oil change, it's excessive in the overwhelming majority of use cases but it will make more money for whoever does the work and not cause a system to fail in a way that comes back to bite whoever installed it.
Sometimes legal departments force them to include those recommendations in order to err on the side of "absurdly overcautious." And sometimes the recommendations are merely prudent! I'm not saying you can wait longer, just that installers may have a motivation to exaggerate.
If you let the fat and oil solidify at room temp and dispose of them in the trash, and if you use regular soap in the recommended amount, and if you septic tank additive once in a while, you will be tearing the problem at the source, and will only need to take care of the tank when it’s time to replace it in 40 years.
Septic tanks are not closed systems they are open and intended to provide an environment that can produce a bio-reactor while maintaining drainage through the soil.
Many good systems don’t need to be drained other than every few decades in fact good systems would outlast the tank and the filtering substrate it’s built on so when the time comes you need to dig out the tank and the gravel and other filtering particulate it used because that is what has degraded.
The problem with septic tanks is that they don’t scale we’ll have one on a large property in the middle no where that 5 people use and it’s a great solution have a bunch of them and worse over use one in particular and you get a polluting mess.
But septic tanks also don’t solve the other problem with western toilets and that is the amount of water they consume which is simply unfeasible for many developing regions.
TLDR; if the septic tank was installed and sized correctly it will outlast you even without pumping it, but it’s not a solution the reason we don’t use them in cities is because they don’t and can’t scale with urban population densities.
Other areas like those in which ground temperatures drop below freezing for long period of time might also require tight tanks and constant pumping since the cold may stop the reaction in the tank so it would surprise me if tanks in places like say N. Dakota would be pumped year before winter to prevent them from freezing shut and overflowing.
RVs have holding tanks that must be emptied. Thus, they aren't called "septic tanks".
But I'm sure the term is used loosely.
Our local township has an ordinance where every residential sewage system (10k residents, not sure how many systems that is) has to be pumped out and inspected by a certified sewage hauler. This way, the homeowner knows about and is required to make simple repairs before the entire system fails.
I suppose there will be very small amounts of minerals that don't break down but they are insignificant.
Note: this isn’t even taking into account the cost of the toilet itself or any plumbing needed.
Basically you've got to learn to crawl before you can run a 10k.
edit: You can get someone who is completely illiterate and cut off from civilization to understand the concept of digging a hole for the shit to go in. This has the added benefit of not requiring advanced manufacturing technology or materials. they just have to dig a hole and move the outhouse top over to the new hole when the old one gets full. This makes them self reliant.
innovations drive change drive more innovation. I recommend Hans Rosling's talks. There is no such thing as the "Third World" anymore, they're all on various development trajectories. Don't think e.g. Somalia is typical for Africa.
It has to be deep enough, and far enough away from a home, road, water source, food supply, etc. Not all communities have a lot of extra land, so you're talking one or two communal toilets, which need to be large to support a large population, and someone has to maintain them.
If you have the land, you have to have money to construct them, as well as labor. Many households can't afford the $1 (that's one US dollar) construction cost, or the household simply can't perform the labor. In some cases, villages will come together to help fund and construct pit latrines, but these are the exception. Most just put up with the shame and disease of open defecation.
Once you do have them, you have cultural issues like India's manual scavenging problem (http://www.thealternative.in/society/manual-scavenging-thoug...) not to mention you literally have to go out and inform millions of tiny remote villages about why and how to change. It's very hard to get people to change.
Assuming outreach of one week per village, for the 600K censused villages in India, that's 11,506 years to just inform and convince them all to build pit latrines. Even 50 outreach teams would take 250 years. With 500 teams you can cut it down to 23 years.
Literally any deep hole practically anywhere is a damn sight better than open defecation straight into the river, on the bank, or all over the streets. And it doesn't take an act of congress to fund it and change building codes, a civil engineer, excavator, and team of union laborers to get this stuff done like it does in the west. You just need someone who is personally motivated and determined and a shovel ideally. like this guy:
https://en.wikipedia.org/wiki/Dashrath_Manjhi
All you need is one person who knows that digging a hole would keep his kid from getting sick and dying and you'd have more trouble trying to stop him from digging that hole for an outhouse.
When that clicks for them. That their kid or wife or husband wouldn't have died if they bothered to dig an outhouse, they will be doing the work and telling everyone they know and also nagging people till their ears fell off when they catch someone shitting in the street.
Hell, I was in Chongqing a couple months ago and saw a teenager literally unzip, in full view of everyone, and pea on (on, not into) a recycling bin. Next to a god damn public toilet.
In the middle of a shopping center.
Near a police officer.
A lot of people just don’t care.
I've seen people poop on the train platform in NJ. Really crazy, but Newark does not open the bathrooms until 7-8AM. So when you're waiting for the 3AM train to DC... what you gonna do?
Taking a shit in the street is perhaps not such a problem if you clean it up afterwards? Culture is hard to change, but perhaps it can be accommodated?
Anyone know which country is this considering?
But when they're not kept up. https://www.theguardian.com/us-news/2017/sep/05/hookworm-low...