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Collapsing building © Daniel FriedmanSeptic Tank Risers
Definition, Need, & Installation of septic tank risers & access ports

Septic tank risers or access covers for deep septic tanks:

This article defines septic tank riser and explains how these components are installed to provide adequate cleaning & inspection access openings to pump & maintain a septic tank, cesspool, drywell, soakpit or similar wastewater disposal system.

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Septic Tank Risers: What if the septic tank is buried deep below ground surface?

Septic tank riser & cover, Seal Isle City NJ Tanner & Chase Gilligam (C) Daniel FriedmanDefinition: Septic tank "risers" are large diameter enclosures placed over the septic tank access covers to permit easy septic tank inspection and cleaning without having to "dig up" the septic tank at each occasion.

A septic tank riser consists of a bottom seal against the septic tank, a round large diameter material made of concrete, PVC (polyvinyl chloride), polyethylene, or occasionally steel that forms a "well" around the septic tank cleanout, and a cover that can be secured at ground level.

Typical septic tank riser diameter is 24-inches but 30-inch, 16-inch and other riser diameters are available. Risers are sold in varying heights from 6" and up.

Watch out: Occasionally, as you'll see in photos here, septic tank risers are made of other materials such as stacked concrete blocks or even wood. Generally these are unreliable and often they're very unsafe.

As the photo just above illustrates (thanks to my grandchildren), both adults and children will stand on or walk over septic tank or cesspool or drywell covers and curious individuals may even attempt to remove the cover.

Falling into a septic tank or even simply leaning over to look into a septic tank can be a quick and ugly death.

[Click to enlarge any image]

Reader question: I was told my septic system needs a riser. What's that?

(May 14, 2011) Charles said:

I was told that my septic system needs a riser. What is that and what does it look like?

Reply: definition & description of septic tank riser

A septic tank riser is simply a large diameter round pipe, typically a couple of feet across, that is placed over the septic tank cleanout opening to extend that opening up to close to the ground surface so that the septic pumping company does not have to dig deep into the soil in order to reach the septic tank cleanout cover for pumping and cleaning the tank.

Watch out: just as a septic tank must have a save and secure and childproof cover, so must a septic tank riser, cesspool, drywell, etc. Boys will be boys, as my grandsons demonstrate, standing atop a septic tank riser cover in Seal Isle City, New Jersey.

The Gilligan boys provide ample testing of the security and curiosity-proofing necessary at site hazards including septic tanks.

Shown below: an easy-to-access septic tank riser at a property we inspected in Norway. [Click to enlarge any image]

Septic tank access riser at a Norwegian property (C) Daniel Friedman inspected in 2008

Indeed we've seen septic tanks partially above ground, and others buried more than six feet deep. It's not necessarily a mistake, and deep septic components may be required by site conditions, but here are some considerations when the septic tank is more than a foot below ground surface:

Septic Tank Riser Requirements & Dimensions

Septic risers are large-diameter "wells" that are placed over a septic tank inlet baffle access port (and possibly outlet) to permit easy access for septic tank pumping, inspection, and baffle repair.

As we detail below, a septic tank riser enclosure must be of larger diameter when the tank is deeper in the soil. Otherwise it is simply not possible for a septic tank cleaning contractor to remove all or even most of the floating scum and settled sludge from the septic tank.

Our illustrations show the septic tank cleaning contractor using a muck rake - essentially a long-handled hoe-like instrument, to break up settled sludge and floating scum so that it can then be pumped out. If the tank opening is deep and narrow there is simply not enough room to perform this job properly.

PHOTO of the septic tank muck raking tool used to break up scum
and sludge layers during pumping.

The result of a too-small septic tank cleaning access opening is that much if not most of the solid waste is simply left in the septic tank, completely defeating the purpose of cleaning the tank in the first place.

PHOTO of septic tank sludge being broken up for tank cleaning

Details of a proper septic tank cleanout are

at PUMPING the SEPTIC TANK

If the septic tank happens to be buried more than just a few inches below ground surface, good practice includes (and sanitary or plumbing codes in some areas requires) installing a septic riser, a large diameter pipe that gives good access to the septic tank for inspection and cleaning.

Steps in Adding or Installing a Septic Tank Riser

TuffTite poly septic tank riser cited & discussed at InspectApedia.com

Illustration: a TuffTite Septic Tank riser, cited below.

PVC or poly septic tank risers will typically include the

septic tank riser itself, or multiple risers depending on the depth of the septic tank below the ground surface

an adapter ring that is bonded and sealed to the concrete septic tank top or existing concrete riser using a butyl rope or other sealant recommended by the manufacturer,

a riser lid that screws in place

How to Install a Septic Tank Riser

Butyl sealant rope gasket used with PVC septic tank risers - cited & discussed at InspectApedia.com

Watch Out: Deep drainfields mean poor septic effluent processing. If a deep septic tank means that the absorption area (leach field or drainfield are synonyms) is deep, such that the top of the soil trenches are more than a foot below ground surface, then the reduction in aerobic bacteria in the soil will limit the effectiveness of the drainfield in reducing pathogens and other environmental contaminants.

Additional septic effluent treatment methods can correct these conditions, but it's useful to keep in mind that there is a difference between successful septic effluent disposal and successful septic effluent treatment. A deep septic tank does not necessarily mean that the absorption area is also deep, since site conditions and use of septic effluent pumps may change the required depth of a drainfield.

Watch Out: Be sure that the septic tank riser and all septic tank covers are sound and secure since falling into a septic tank can be fatal.

See SEPTIC & CESSPOOL SAFETY .

Unsafe septic tank cover discovered by simple exploration - we roped this area off and placed heavy plywood over the opening - it was by a children's play area.

The two septic tank access risers shown here are dangerous and could easily involve a fatality. At below left is a collapsing home made septic tank made of concrete blocks over which someone placed a concrete cover and slabs of slate to try to cover this dangerous hazard - an inadequate response.

At below right was a two-concrete-block high septic tank riser provided at a mobile home park in New York. The site manager had simply left the septic tank cover off.

Unsafe septic tank cover discovered by simple exploration - we roped this area off and placed heavy plywood over the opening - it was by a children's play area.

Septic Tank Riser Installation Instructions

Orenco PVC septic tank riser on concrete septic tank - cited & discussed at InspectApedia.com

 




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Reader Comments, Questions & Answers About The Article Above

Below you will find questions and answers previously posted on this page at its page bottom reader comment box.

Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

On 2019-05-26 by (mod) -

Yes certainly - if the break allows ground-water or surface runoff to enter the septic tank it will cause drainfield flooding and potentially ruin.

Watch out: also a cracked riser might create a risk of death if someone walks over or near the riser cover and it collapses to send someone into the septic tank.

Keep people away from the septic tank with the broken riser, and have the damage fixed promptly.

On 2019-05-25 y miiiii

Does a broken, cracked, or leaking riser cause a septic tank failure?

On 2019-08-27 by (mod) - Can I use PVC risers or do they have to be cement?

Cindy the final legal answer to your question is in the hands of your local building or plumbing inspector. However most jurisdictions permit use of plastic or concrete septic tank risers provided

- the septic tank riser is properly installed in accordance with the tank and riser manufacturer's instructions - that will normally include

- selection of a riser and riser cover that will be safe including child-proof

- proper sealing of the riser to the septic tank lid - often using a butyl rope caulk/sealant at the PVC riser adapter ring and also at the bottom edges of the riser itself

- selection of a riser and cover properly selected for strength depending on site specific conditions like depth of backfill and possible exposure to
vehicle traffic

On 2019-08-26 by Cindy

Can I use PVC risers in WI or do they have to be cement?

On 2019-05-02 by (mod) - How deep should septic tank riser covers be buried from the surface?

You can leave it exposed or you can bury it under 14 inches or so of soil in order to be able to have your grass grow in that spot

Watch out: If the septic tank riser cover is NOT above ground there is risk of surface runoff and groundwater leaking into the septic tank, flooding and destroying the system unless the cover is water-tight.

On 2019-05-01 by Bob

How deep should septic tank riser covers be buried from the surface?

On 2017-01-22 by Susanmac

I just placed a modular for storage on my property. The house burnt down near the septic. I cannot afford to build a house now, but hope to hook up the office /storage to the septic. Can I do this with the tank being approximately 200 feet away?? How will the slope of the pipe work? Can it stay above ground or have to be buried to meet the tank?

On 2016-06-07 by (mod) - small septic tank openings and risers

Steph and others:

There is no chance whatsoever that your septic tank is 15" in diameter as you suggest.

If you meant to say that your septic tank access openings are quite small, perhaps just 15" in diameter, that might be the case but you can and should install a larger diameter access or tank riser; it is very difficult to manipulate tools and pumper tank hoses to do a good septic tank cleanout job through a small tank opening.

To protect our readers' confidence in the impartiality of InspectApedia we do not sell anything. Check with your local septic suppliers.

Watch out: be sure that your "light, easy to remove" septic tank lid is also locked and childproof lest a kid fall in and die.

On 2016-06-07 by Anonymous

I need a septic tank lid with an access port for emptying a portable septic from a camper without having to slide a heavy lid. Do you have these?

On 2015-06-11 by Nada

my lids are about 6 inches into the soil and are three ugly brown patches on my main lawn how to i disguise them

On 2015-05-19 by STEPH

Our tank(s) are 15 inches in diameter. (there are 3 of them)why are 15/16 inch risers so hard to find and why are risers so expensive?

I would think that anyone could simply purchase large pvc/drain/culvert pipe and make their own riser. What do you think?

Why doesn't your comapany sell the 16" diameter risers?


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