What is a manure pit? Types, problems, and safety

A manure pit is a structure that stores liquid or slurry manure until it is pumped out and applied to fields. The common types are deep pits under slatted barn floors, shallow pull-plug pits that drain to outside storage, above-ground tanks, and earthen basins. Pits develop crust, settled solids, foam, and odor, and every one of them can produce gases that kill people.

What is a manure pit?

A manure pit holds manure between the barn and the field. Most livestock operations cannot spread every day, so manure gets stored for months and applied when the ground and the crop calendar allow.

You will also hear the term slurry pit. That is the usual name in the UK and Europe, where liquid farm manure is called slurry and the structures that hold it, pits, tanks, and lagoons, are called slurry stores (UK HSE, Managing slurry on farms). Same thing, different side of the Atlantic.

How many are out there? Penn State researchers, summarizing federal survey data, cited roughly 127,000 manure storages on about 98,000 U.S. farms, about 16,600 of them enclosed pits under solid or slotted covers (Murphy and Manbeck, 2014).

What are the main types of manure pits?

Deep pit under slats. The barn floor is slatted and the pit sits directly below it. Purdue Extension describes deep pits under animal housing as common for swine and dairy slurry (Purdue ID-352). A University of Minnesota study identifies deep-pit storage as the main design on swine farms in Minnesota, Iowa, and Illinois, pumped out once or twice a year (Yan, University of Minnesota, 2016). As one documented example, a multi-university study of two 1,000-head Iowa finishing barns described concrete pits about 8 feet deep, sized for a year of manure and emptied each October (Hoff et al., 2006).

Shallow pit with pull plug. A shallower pit under the slats is drained every so often by pulling a plug, sending manure to an outside lagoon or storage. Purdue Extension notes this can reduce odor inside the building, but overall farm odor can go up if the drained manure is not properly stored and treated (Purdue AQ-2).

Above-ground tank. Concrete or steel tanks outside the barn, used for swine and dairy slurry. Purdue notes they need provisions for agitation and pumping.

Earthen basin. An excavated or bermed storage with a compacted clay or concrete liner. Not to be confused with a treatment lagoon, which is designed with extra water so bacteria can treat the manure. The difference is covered in how manure lagoons work.

How is a manure pit emptied?

Mostly in two windows. University of Minnesota Extension notes that liquid manure is agitated and pumped in short windows in spring and fall, and that fall application should wait until soil temperature falls below 50 F and come before the ground freezes (UMN Extension). Storage is sized to carry the operation through the months in between. Nebraska Extension cites 180 days as the current minimum storage period for new manure storage (UNL Water), and your state may set its own rule.

Before it is pumped, a pit is agitated so the settled solids come up with the liquid. That step is where most of the time, fuel, and danger sits. More on cutting it down in manure agitation and pumping.

What problems do manure pits develop?

Crust. Fiber from feed and bedding floats and mats on the surface. Purdue notes that cattle manure tends to form a crust that holds in odor, while swine and poultry manure generally does not. A crust can cut odor, Purdue says natural crusts may reduce it by about 50%, but it also has to be broken at every pump-out and it gives flies somewhere to breed. See what causes manure crusting.

Settled solids. Heavier fiber and grit sink and compact. Every inch that does not come up during agitation is storage you no longer have.

Foam. A University of Minnesota survey of mostly Iowa producers found foam in about 24% of 1,334 deep pits, and about 59% of producers had at least one foaming pit. Thirteen producers, close to 10% of those with foam, reported a flash fire or explosion (Akdeniz et al., 2013). Foam traps methane under the slats, which is why it is a fire problem and not just a capacity problem. Not all foam is the same, and treating it starts with identifying which kind you have. See manure pit foam and why pit foam is a flash fire hazard.

Odor. Every pit makes some. A pit that is stratified into a crust on top and a hard layer on the bottom tends to hold gas and release it all at once when you agitate.

How dangerous are manure pit gases?

Deadly, and the numbers have not improved. Read this section even if you skip the rest.

Penn State Extension names the four manure gases: hydrogen sulfide, methane, ammonia, and carbon dioxide. Hydrogen sulfide is the one most often associated with deaths. It deadens your sense of smell as the concentration rises, and above 700 ppm it causes rapid loss of consciousness and death within minutes (Penn State Extension). OSHA lists 100 to 150 ppm as the range where it paralyzes the sense of smell (OSHA). If the smell goes away, you are not safer. You may be in more danger.

The pattern in the deaths is grimly consistent. Penn State's summary of Purdue research covering 1974 to 2004 counted 91 deaths in manure storage incidents. About a third happened during repair or maintenance, 22% were people attempting a rescue, and 21% were under 16 (Penn State Extension). NIOSH documented a dairy farmer who went into a pit to clear a clogged pump intake and his brother who died going in after him, and five farm workers who died entering the same pit one after another (NIOSH Alert 90-103).

It is not history. Purdue's 2025 summary of agricultural confined space incidents recorded four incidents involving livestock waste pits or lagoons that killed 10 people that year, six of them in a single Colorado incident (Purdue, 2025).

And it is not only a confined space problem. In August 2016 a 29-year-old Wisconsin farm worker died beside an open outdoor manure basin after running an agitator around 3 a.m., and 13 cattle in an adjoining pen died too. CDC investigators pointed to hydrogen sulfide and noted calm, very humid air and a temperature inversion that night (CDC MMWR, 2017).

What are the rules for working around a pit?

These come from extension and federal safety guidance, and none of them are optional.

• Never enter a manure pit. Not to fix a pump, not to grab a tool, not for a few seconds. It is the first precaution on NIOSH's list (NIOSH, 1993), alongside posting hazard signs and making serviceable parts reachable from outside the pit.
• Do not go in after someone. OSHA says not to attempt a pit rescue unless you are trained and wearing proper breathing equipment, and to call the fire department or rescue squad immediately. Would-be rescuers are about a fifth of the deaths.
• Lower the level before you agitate. Iowa State recommends waiting until manure is 1.5 to 2 feet below the slats, keeping nozzles below the surface, and not aiming them at walls, pillars, or corners (Iowa State, 2016).
• Ventilate and clear the building. Run ventilation at full during agitation and keep people, and where possible animals, out.
• Watch the weather outdoors. Calm, humid nights and inversions can hold gas near the ground.
• Keep kids away. Federal child labor rules bar youth under 16 from working inside a manure pit (OSHA).
• Use a monitor. A personal hydrogen sulfide monitor costs far less than what it prevents.

The full breakdown of each gas is in manure gas dangers.

Where does pit treatment fit?

A pit is a biological system whether you meant it to be or not. When the bacteria that break down fiber fall behind, you get the stratified pit described above: crust on top, solids packed on the bottom, gas trapped between, and agitation hours that keep growing.

PitCharger products are formulated for specific manure problems. Manure Digester is the flagship monthly treatment for pits and lagoons, LTC-E is built for high-fiber manure and crusting, and N-Loc is for maximum odor reduction. Foam is diagnosed first, then treated, because different foams need different approaches.

Treatment does not change a single safety rule above. You still lower the level, ventilate, and stay out of the pit. What it aims to change is how much material is fighting your agitator and how much gas is held under a mat when the prop hits it.

For hog operations, a common starting point is about one gallon per month per 1,000 head. Most producers should notice a difference within the first month, with continued improvement through the second and third months, and significant results are normally measured after about six months. Work the numbers in the calculator or get a treatment plan.

Frequently asked questions

What is the difference between a manure pit and a slurry pit?

Nothing but the name. "Slurry pit" is the common term in the UK and Europe, where liquid manure is called slurry. In the U.S. the same structure is usually called a manure pit or deep pit.

How deep is a manure pit?

It varies by design and species. As one documented example, a multi-university study of Iowa finishing barns described deep pits about 8 feet deep under the slats, sized for a year of manure. Shallow pull-plug pits are much shallower, and outside earthen basins are often deeper.

Why do people die in manure pits?

Mostly hydrogen sulfide. It deadens the sense of smell, it is heavier than air so it collects low, and at high concentrations a person can collapse within a breath or two. Rescuers die because they go in without breathing protection. Penn State's summary of Purdue research found 22% of deaths were would-be rescuers.

When is a manure pit most dangerous?

During and right after agitation and pumping, when gas trapped in the manure is released all at once. That is when ventilation, distance, and keeping people out of the building matter most.

Can I treat a manure pit to reduce crust and solids?

Yes, biologically, over months rather than days. Biological treatment adds bacteria to help break down the fiber behind crust and settled solids. It does not replace agitation, and it does not change any safety rule. See manure additives compared for how the different product types stack up.