Septic Tank Size FAQs #2

Septic tank repair or replacement cost FAQs
Shared septic system components FAQs
Temporary heavy septic system use FAQs
Time to fill up a septic tank FAQs

Septic Tank Dimensions FAQs

Can my septic tank size be 12 feet deep?

Can I use a a 12 ft deep tank for septic tank? On 2021-01-29 by timothy mathews -

by (mod) - besides septic tank depth, consider its shape and total capacity

Just above we include a sketch from Antigo Block Co. showing a typical single compartment septic tank dimensions. That entire tank is less than five feet in depth.

12 feet deep is about twice a typical septic tank maximum depth, and so deeper than we usually see for a residential septic tank - but the depth isn't the whole question; it's overall tank shape as well -

see SEPTIC TANK SIZE  where septic tank shape and dimensions are included. There you'll see that the deepest septic tank we list is just 64 inches.

Whle bigger septic tanks are generally perfectly fine in residential application, the septic tank dimensions including not just depth but width and length may be significant in its ability to function and to be properly serviced.

As an example of the importance of considering all of the septic dimensions, a septic tank used on rocky sites may be more shallow than normal and raises questions about its ability to function properly - as we explain at DIFFICULT SEPTIC SITE DESIGNS 

Watch out: you might confirm with a local septic tank cleaning service that such a deep septic tank can be effectively cleaned.

Watch out: check with your local building or plumbing code officials on the largest septic tank that they will allow on your building site.

Watch out: you also don't give the other septic tank dimensions. While the largest typical residential septic tank might be around 3,500 to 4,000 gallons, if you need and are achieving that volume by a septic tank whose depth is greater than its width and length, I'm doubtful about its performance.

While usually we're concerned about the sludge accumulation rate and loss of net free area for treating septic effluent in septic tanks that are too small, a septic tank that is "too big" or "too deep" for its application may not be serviceable.

Here are some authoritative research papers on

Septic Tank Size vs Performance and Sludge Accumulation

• Cotteral Jr, Joseph A., and Dan P. Norris. "Septic tank systems." Journal of the Sanitary Engineering Division 95, no. 4 (1969): 715-746.
• Gray, N. F. "The influence of sludge accumulation rate on septic tank design." Environmental technology 16, no. 8 (1995): 795-800.
  
  Abstract:
  
  Sludge accumulation was determined in 28 septic tank systems of various sizes and configurations. Sludge accumulation rate in septic tanks declines steadily over time, with the rate significantly less after 12 months. Specific sludge accumulation per capita per day falls from 0.254 l/ca/d (92.7 l/ca/y) over the first 6 months of operation to 0.178 l/ca/d (64.9 l/ca/y) after 60 months. The mean sludge accumulation rate, irrespective of sludge age, was 0.234 l/ca/d (85.3 l/ca/y).
  
  Increasing the desludging interval significantly reduces the volume of sludge produced, and so the operational cost of the unit to the owner. Longer sludge ages result in much more stabilised sludges which do not need to be disposed of to a sewage treatment works.
  
  When empirical data is used to evaluate design, then a standard 27201 septic tank serving a population of 4 should require desludging every 5 years, while retaining a minimum hydraulic retention time of 2.0 d and a liquid settlement volume of 48% overall.
  
  There is an increasing carry over of solids from the primary chamber of some septic tanks with sludge age. Traditionally a short desludging interval has been recommended to prevent the possibility of excessive solids loss from tanks. However, there is potential for better designed systems to take advantage of longer sludge ages, with mutual benefits for owners and the environment.
• Kirjanova, Ala, Mindaugas Rimeika, and Regimantas Dauknys. "Designing and testing a septic tank for a single household." Environmental Engineering & Management Journal (EEMJ) 13, no. 3 (2014).
• Laak, Rein, Kent A. Healy, and Dan M. Hardisty. "Rational basis for septic tank system design." Ground water 12, no. 6 (1974): 348-352.
• Perkins, Richard J. "Septic tanks, lot size and pollution of water table aquifers." Journal of Environmental Health (1984): 298-304.
• Philip, H., S. Maunoir, A. Rambaud, and L. S. Philippi. "Septic tank sludges: accumulation rate and biochemical characteristics." Water Science and Technology 28, no. 10 (1993): 57-64.
  
  Abstract: A three year field and investigative study carried out on 33 individual sanitation systems showed that the frequency of septic tank emptying could be at least 5 years, corresponding to a sludge accumulation rate of 0.21/user.day. This value should be included in the calculation of septic tank sizing.
  
  Other data showed within a septic tank the methanogenesis is only effective after 2 years of operation. Thereby a septic tank should not be desludged before this period of time. At last, among all the physico-chemical parameters monitored to study the sludge quality, the best indicators of system failures were both the solids (TS and VS) and soluble matter (COD and some VFA).
  
  Then, biochemical study of septic tank sludge showed that the main hydrolytic enzymes (cellulase, phosphatase, protease, lipase and urease) are present in septic tank sludges and linked to the insoluble particles. Their solubilization with different solvents (buffers, surfactants…) showed each enzyme was linked in a different way.
• Rahman, Md Mujibur, A. H. M. Shahidullah, and M. Ashraf Ali. An evaluation of septic tank performance [PDF] (1999). WEDC, Loughborough University, 25th WEDC Conference,Addis Ababa, Ethiopia, local copy saved as Septic-Tank-Performance-Rahman.pdf
  
  Excerpt: From the present study it appears that the septic tank effluent quality varies significantly with the composition of domestic wastewater.
  
  For septic tanks treating wastewater from toilets only, effluent quality was relatively poor. With the addition of kitchen wastewater (sullage), the effluent quality wit respect to BOD, COD, TOC and SS improved significantly.
  

Septic Tank Missing or Completely Blocked with Solids FAQs

My uncle lives on a property with no legal septic system, just a home-made hole in the ground.

if i have an uncle living on property w/o a legal septic, can i be charged if i have a legal septic and he doesnt? (just a hole in thr ground with rocks for drainage.) On 2021-10-12 by zack jennen

by inspectapedia.com.moderator (mod) - Watch out: for a cesspool or something even less functional and more dangerous

@zack jennen,

Watch out: What you describe is unsafe and a danger to your uncle - the occupant - as well as to neighbors and local waterways.

Ultimately, you as the property owner are responsible for meeting any building and health code regulations.
You could, of course, contact your local building official, who is the final legal authority, and find out what the requirements and potential penalty are.

Having said that, no jurisdiction in the US will allow the system your uncle is using. And quite apart from the legalities, please recognize the damage to the environment and neighboring properties that is occurring by allowing untreated wastewater and sewage to enter the soil.

If you're the property owner of the site you describe, your immediate focus should, in our OPINION, be on stopping an unsafe and unsanitary health hazard at your property by having a properly-designed septic system installed.

See CESSPOOL SAFETY WARNINGS

Can you have a septic system with no septic tank at all, just a leach field ?

Can you have a septic system with just a leach field and no septic tank? On 2021-10-05 by Dennis b

by inspectapedia.com.moderator (mod) - Nope - without a properly sized and designed septic tank the septic leachfield would quickly clog and fail

@Dennis b,

A properly working septic system requires more than just a leach field.

If a building's waste was allowed to flow directly into a leach field, the solids contained therein would quickly render the leach field unusable not to mention damaging to the environment.

A private onsite septic system means that the waste from your building drains (sinks, showers, toilets) goes into a septic tank which retains the solids and lets the effluent flow into the soils on the property (leach field).

To avoid contaminating the environment, including nearby wells and waterways, septic system wastewater must be treated to reduce its pathogenicity.

Luckily naturally-occurring bacteria found in the septic tank AND leach field soils accomplish this task - as long as the septic system is working properly.

In a standard septic tank and leach field system, about 40% of the treatment of sewage wastewater occurs in the septic tank, and the remaining 60% occurs in the leach field trenches and surrounding soils.

Please read more at:

COMPLETE HOME BUYER'S GUIDE TO SEPTIC SYSTEMS

Shared Septic Tank or Leachfield FAQs

Is it Safe and OK to share a septic drainfield with another homeowner?

I am in the process of getting a year around cottage. 2 homes shares only Tile bed. This tile bed is in my property. Question is-

1 Having Tile bed in my property is that Safe and OK to have?

2.i have a 3 bedrooms and 1 full washroom so if I plan to put an extra washroom then is the same Tile bed is good enough to handle the job?

3. How often I have to do any maintenance or cleaning for Tile bed. I know there is a pump out for Septic Tank.

Thank you - Ramanan 14166706467 On 2019-06-22 by Ram

Reply by (mod) - 2 homes sharing 1 septic tile bed

Watch out: There are a number of issues with the situation that you described.

Both legal that you need to discuss with your attorney and practical and functional.

With a neighbors septic tank draining onto your property you have no control over what's being done or not done properly on that side that isn't going to cause a failure in the system.

We also don't know if the capacity is adequate. It's also unlikely to be a legal installation. I think there could be resale issues as well as septic failure issues.

And we don't know how you're going to decide who pays for repairs, repalcement, or the cost of a sewage backup into the home if/when the drainfield fails.

Septic tank to fill-up time FAQs

How long will it take for my "capped off" septic tank to fill-up?

Totally love this info. What a Blessing. I think I have a leak. My septic fills in 3wks max. Pls call 2193312035

How long does it take 3 BR single 1000 gallon septic to fill up that's been capped off. Family of three On 2018-08-07 by Cecilia Ballard

Reply by (mod) - zero days if the system is already in normal use as a septic tank is normally always full - days to a week if the tank was just pumped.

Cecelia

Watch out: if your septic tank has been "capped off" so that it is nothing but a sewage holding tank, you've got just 2-5 days before a typical 1000 gallon septic tank will be re-filled after it has just been completely empties.

So you're risking a sewage backup into the home.

You can extend that time slightly by using as little water as possible.

More generally and for an actual septic tank plus drainfield system, it is perfectly normal and correct for a septic tank to be filled at all times except immediately after having been pumped out for a cleaning.

As waste water enters the septic tank it pushes a like volume of a fluid out of a septic tank and into your soakaway, leach field, or absorption bed.

If your septic tank was a 1200 gallon residential tank, our septic tank size table at SEPTIC TANK SIZE says that tank can handle the typical number of occupants in a 4 bedroom home,

Details of how much wastewater your home is likley to produce are found

at WATER QUANTITY USAGE TABLES

See septic tank and drainfield sizing and design details at SEWAGE FLOW & DESIGN FLOW ESTIMATES 

Septic Tank / Drainfield Repair or Replacement Cost FAQs

What's a new, expanded septic sytem going to cost me?

I'm considering purchasing a 6000 commercial building for retail space.

It has an old septic system that I understand needs to be replaced due to real estate laws in Rhode Island. It was formerly a tool shop. Any idea what this kind of thing will cost me? I have heard horror stories of 20-60K.

I may also want to open a small coffee shop on the site as well. What type of specialist would I deal with to check out and arrange for these types of things? Any info you can provide will definitely help! On 2018-07-26 by Anna V

by (mod) - factors affecting septic system repair or replacement cost

I'm sorry to say, Anna that your question, as posed, is one I can't answer: it's sort of like saying "how much does a house cost?"

The cost to replace even a simple broken pipe connection ranges from a few hundred dollars if the connection is easily accessed, to over $1000. if someone has to locate the break and then use a backhoe to excavate just to get to the point of repair.

The range of possible answers for replacing a whole septic system, when we have not one iota of information to narrow down the question, is so huge as to not be helpful.

$20K TO $80K or more for septic system installation or replacement is possible in generic terms. Here are some of the factors determining the cost of septic system installation or replacement:

You need to know

- the system requirements - daily wastewater flow

- the site size and encumbrances and space available

- the soil properties, percolation rates

- the typical costs for Rhode Island installations (or other country, state, or province where your system will be installed)

- special encumbrances that affect cost: needing to route sewer pipes under parking area, for example, and cost to safely abandon the existing system.

Septic Tank & System Temporary High or Extra Loading FAQs

How many days in a row can a septic tank spec'd for a 4 bedroom house handle 15 people?

How many days in a row can a septic tank spec'd for a 4 bedroom house handle 15 people?

The house is going to be used as a holiday home so it is only occupied on occasion maybe 30% of the year with variation between 4 to 15 guests during those times. I am looking to purchase it, so it is already built with a "4 bedroom sized" tank (Vermont) just curious if it can handle my families needs from time to time. thanks! On 2018-03-11 by S

by (mod) - Septic tanks and drainfields have to be handle the highest anticipated wastewater flow or your risk drainfield failure

S

It's not just the septic tank - it's the absorption bed or soakaway bed capacity that's critical.

In the article above see the table titled

Septic Tank in Gallons Size Based on Number of Bedrooms

but a normal 4 bedroom home is assumed to support perhaps 8 people. Your number is double that.

So you probably need a 2000 gallon or 2500 gallon septic tank AND your septic absorption field needs to be able to handle the surge in wastewater volume as well.

See SEPTIC DRAINFIELD SIZE

OR your septic engineer might design a large septic tank with a dosing system to spread out the effluent disposal over a longer period to perhaps permit a smaller drainfield.

See GRAVITY/SIPHON DOSING SYSTEMS
and
see PRESSURE DOSING SYSTEMS