Is That Bad For The Septic? What the Engineers Say

While divining, fortune telling and snake oil have  gone the way of the past sketchy septic advice is still out there. There are so many do this not that’s out there. Now I know septic system posts are a niche audience but maybe you don’t have a septic but still harbor an intense need to know. If that’s the case you’re weird but meh, read on. Septics are a big deal in the country and can let you down in a big way when you lest expect it. But did you know about 25% of homes in in the US use a septic system? We work with a few septic engineers and installers and owning one I always ask for advice. Guess what there’s no consensus there either. So I decided to look into the scientific literature and see what could be learned.

For those of you that don’t know but want to here’s a little breakdown of how water and sewage work in the country. First and foremost we don’t pay a water bill but that also means we have no one in government to call on when there is no water or the poop won’t go away. We have wells, maybe a water treatment system and septic systems that we must pay for and maintain ourselves. The cost of a drilled well and pump is about $6000 USD but can vary if you have to go deeper, dug wells aren’t really a thing any more but they are cheaper. Other than a pump for $500 or so every 15 years this is almost always a one time cost.

Water treatment can range widely for nothing to including things like iron filters ($500), water softeners ($600), UV lights (400), arsenic purifiers ($1100), reverse osmosis ($300) units and sulfur reducers ($900). All of these prices are unit only and don’t include installation. These are all appliances so they wear out and have parts that need regular changing. 

 A septic system can cost between $5000 – $40 000 USD but usually falls somewhere lower than about $12 000. This part of your system though has a finite lifespan so were always trying to get the most of it. When my accountant mom’s failed the first thing she did was cancel our trip to Spain, how rude! The second thing she did was sit down and crunch the numbers. Her system was a little more expensive than average since she lives on the water and I would say was a tiny bit north of that average $12000 cost but not by a whole lot. We got off easy at about $6000. She had gotten about 20 years out of the old system and she decided that it was still a bit cheaper over the long run than paying a city water bill. The only catch is you have to pay it all at once.

There’s a lot of confusion in country circles about what is in fact best for your system even among installers. Is it any wonder that we’re confused when sentences like this appear in the engineering literature.

“Today, there is still no clear understanding and consensus among practitioners on the design, construction materials, installation, operation, maintenance, and performance of septic tanks. This is further compounded by prescriptive procedures and practices used by different state and local agencies.” – Solomen et al., 2007. Real time monitoring of operational characteristics in septic tanks.

What is a septic system

A septic system aka an on-site water water management system is usually some sort of settling tank (aka the septic tank) and a septic field (aka drain-field). Waste goes into the tank at the bottom settles and some breakdown occurs here. The watery stuff slowly drains into the field where there is oxygen and is filtered and cleaned and the resulting water is safely let back out into the environment.

Most tanks are made out of concrete and have one (sometimes more chambers) but the field can be gravel, sand, peat moss or a biological aerator depending on the lot and where it’s located and in order of expense. When it fails it backs up into your house or more often your lawn and it smells just like you think it would. Usually failure is due to the field clogging over time.

What I’ve heard

There’s a lot of chatter about septics in the rural places not only because there is relatively little else to do. We all want to spend less on poo after all. These are the common things I’ve heard but rest assured there is a ton more! Sometimes you even hear “Billy-Bob down the road did this crazy thing to his system and it lasted 50 years!’ Others say Biily-Bob’s story is a rural myth. So below are the common ideas but what is the facts?

  • Coffee grounds are both bad and good
  • Bacon fat is bad
  • Never use bleach or anything anti bacterial 
  • Toss some rotten liver in the tank about monthly
  • Ultimately once it reaches a certain number of gallons it’s done
  • Try not to put too much in at once 
  • Never let a truck drive over it
  • There must be plants over the field maybe specifically grass
  • Don’t let gray water into the system, even if that’s against the law
  • You don’t need to pump at all or do it every year

Fun facts I learned along the way

I actually had a tricky time finding goods stuff out there in the peer-reviewed data with there but I got there eventually.  Before we get in to myth busting or proving here are some of the crazy new things I’ve learned:

– 45% of the management is done at the tank level. Since the field is the expensive non-reusable part we tend to obsess over that but your simple tank is doing a lot of the heavy lifting!

– The water that comes out can be indistinguishable from municipal treatment sources. In other words the final product of your septic system might be just as clean as the source point for municipal drinking water, isn’t that cool?

– A 2/3 reduction in water usage is necessary to reduce not cure malfunctions by 50%. So chances are you can’t use less and keep going for very long if your system is failing. But you’ve only got half a chance and you might have to do your laundry elsewhere.

– Dosing the field reduces the chances of clogging over gravity. So if you have a timed release pump system that delivers a certain amount to the field regularly that’ s better than letting it go as it wishes by gravity alone.

– Level fields last longer than those with a grade of more than 5%. Probably because the extra bits settle more evenly than all ending up at the end over time.

  • Typical lifespan is 15 -20 years but they can last for 50. A girl can dream right?
  • What happens to the ‘stuff’ that’s pumped out of your tank. Well it goes on for further processing often into large peat fields that are isolate by membranes from groundwater. Often the sludge is further treated with biological processes like bacteria to enhance breakdown. Once it’s fully treated it’s tested for human pathogens before it ultimate goes to its final destination.

Things that work

This is what you’re all here for right separating myth from science. It took me a long, long time to find these gems and beyond this advice there is actually a lack of consensus. I even had my septic installer friend look over this to make sure you’re not being led astray. These are the only things you can do to extend the life of your system that science has found. I focused foe the most part on extending your investment but following this advice not only saves you money it also saves the environment. So here’s what we actually know!

Use (way) less water

The best thing you can do to extend the life of your field is to minimize water use in the home. 50 gallons per day per person is considered average but getting to 25 gpd per person is considered optimal. Since we don’t have water meters in the country and our wells are constantly refilling it’s hard to know what you are using. My mom has an option to see her gallons per day on her waters softener/iron filter but we don’t have that option. If one of your treatment devices has this option turn it on and pay attention!

 Limiting your water use works by increasing retention time which in turn increases treatment level of effluent with in the system especially the tank. If you’re using too much water waste leaves the tank before it’s ready and starts to clog the field. You should also know how big your tank is and not add over half that volume to the system with in three hours. So how do you cut back well the toilet is biggest offender then bathing and clothes washing. Don’t do things like flush the toilet to get rid of a Kleenex and you could consider not flushing every single time. During droughts you might here the awful phrase “If it’s yellow let it mellow, if it’s brown flush it down,” because there really isn’t another option. But could you say make a point to all use the same toilet in the evenings after getting home from work and the last person to go to bed flushes? What if you’re home alone for the day? For baths and showers just be mindful of how much water you’re using and do you really need a bath everyday or could you make it to two? For laundry re-ware items, wash your sheets half as often and share a towel or two for a week after all you’re very clean when you use it.

Harris et al., Reducing the Risk of Ground Water Contamination by Improving Household Wastewater Treatment. Teaxas A & M.

 In particular be very careful of water softeners backwash as it should not go into tank if possible. Instead if your local laws allow it should be diverted to gray water. Here it’s not technically (ok at all) legal but most plumbers will hook your water softener up to grey water. If it does enter the system make sure it runs at a minimum treatment level and only as often as you actually need it. It could be worth investing in a new one that monitors whole home water use and only operates when actually necessary. Plus then you can play the lets use less water game. 

But less gunk in

Here we get into the old coffee grounds debate guess what they are bad, very bad because we make a lot of them every day. Well at least at my house. In general you want to avoid putting any solids into the system. Some that come from the throne are unavoidable. But being conscious of it as a new years resolution two years ago I cut my toilet paper use by half by just making a point to only take what I need.

Officially avoid suspended solids and limit their size, this causes increased oxygen demand which taxes the field. So DO NOT use a garbage disposal at all for heaven’s sake! Solids ideally will be goo-ified in the tank but the more you put in and the bigger that are the more likely they are to pass into the field and start the clogging process. Solids that make it into the field increase oxygen demand and shorten the lifespan of the field.

What about the ‘other’ stuff

We’ve covered solids in general but what about all that other stuff? Septics will work forever as long as you only put water through the system but that’s not life right? Life involves trade-offs! We hear things like cleaners are bad but you need to clean your kitchen to an extent so not everyone comes down with salmonella and listeria on the regular. Some country folk won’t even let bleach in the house but is that the right course of action?

Here’s something I didn’t realize. Oils and grease are hugely impactful on septic systems. Oils and grease should be wiped from cooking utensils with paper towels and disposed of as solid waste before washing. Oils and grease are largely responsible for what we are pumping out on the regular. Naturally occurring bacteria are responsible for degrading the stuff and the bacteria that break down fats and oils don’t play well with those that break down poo. We want to keep the poo bacteria in control and happy so limit the competition they have from grease and fat bacteria by not putting too much in.

Solvents and cleaners unless they are biodegradable flow through the field and back into the environment but what had how much is safe to use? Plus those germ killing products kill those bacteria we’re trying to keep happy in the system and that’s bad. But who wants to smell like a swamp? Thankfully septic engineers understand life is a trade off and so this had been studied.

The use of bleach solely for disinfecting purposes and dealing with pesticides is okay. Household cleaning chemicals do interfere with the bacteria in your system a few cups, pints, quarts and gallons each week are considered low, low-moderate, moderate-high and high risk respectively. So aim for less than 2 cups of household cleaner use per week including soaps.

Septic additives with cleaning ingredients do more harm than good and those without are generally not considered necessary. Since it’s not a regulated industry ingredients won’t necessarily be listed on the box. If you decide to use them make sure you know and understand what all those ingredients are and none of them are essentially cleaners. As for that rotten liver best to put it in the blender first  to reduce the size of the solids. According to research this is all unnecessary.

To pump or not to pump

The answer is pump and as gross as it it be there when it happens so you can see. If you’re tank is full of sludge pump more often. Also ask your septic professional what he/she thinks. Five years is considered a minimum but for bigger households 3 years or even every year can be recommended. Also leave a few inches of sludge so that the bacteria are maintained.

Other other stuff

Aerobic (often agitated) systems are more prone to issues such as changes in the environmental conditions. Have the system inspected at least three times a year to minimize issues, especially since they are so expensive.

Drain fields, particularly sand must be covered by vegetation it does not however have to be grass. The only concern with vegetation type is that the roots will not be able to enter the drain field and cause damage so check that first.

Its probably best not to let have machinery drive on the field since it can crush the pipes leading to faster clogging. The systems however are designed to take weight to a point.

So there you have it everything science and engineering journals have to say about how to care for and extend the life of your septic system. Billy-Bob’s rotten liver be damned! Even if no one reads this ever, I learned a lot putting it together so I’m pleased. Was any of this new information for you? What is the craziest septic rural-legend you’ve heard?

8 thoughts on “Is That Bad For The Septic? What the Engineers Say

Add yours

  1. That was a good read, thanks! 🙂

    We are on septic system for our toilets and kitchen sink. All other water (bathroom taps, shower, laundry) goes down into a separate grey water system which settles, then pumps out via a garden hose when it’s full. I use it to water the orchard or field sometimes. I’m always careful to cut water usage not just to the septic tank but in general too, as we are on rainwater tank – and it doesn’t rain a lot here!


    1. That septic set up sounds crazy to me here where everything from the house goes in. We’re blessed with an ample water supple here usually here for the wells but over the last 4 years we’ve been having drought conditions every summer with global warming. Summer of 2016 was particularly bad. I’m glad you enjoyed it!


      1. It’s a good system as it takes some pressure off the septic and some of my cleaner waste water gets recycled onto the trees. I’ve got a bore water pump too, but I’ve never had it tested to see if it’s drinkable (used mostly for watering).


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