三格化糞池由相聯的三個池子組成，中間由過糞管聯通，主要是利用厭氧發酵、中層過糞和寄生蟲卵比重大于一般混合液比重而易于沉淀的原理，糞便在池內經過30天以上的發酵分解，中層糞液依次由1池流至3池，以達到沉淀或殺滅糞便中寄生蟲卵和腸道致病菌的目的，第3池糞液成為優質化肥。
The three compartment septic tank is composed of three connected tanks, the middle of which is connected by fecal pipes. It mainly uses the principle of anaerobic fermentation, the proportion of fecal and parasitic eggs in the middle layer is greater than that of the general mixed liquid and is easy to precipitate. The feces are fermented and decomposed in the tank for more than 30 days, and the fecal liquid in the middle layer flows from tank 1 to tank 3 in turn, In order to precipitate or kill parasite eggs and intestinal pathogenic bacteria in feces, the fecal liquid in tank 3 becomes high-quality chemical fertilizer.
新鮮糞便由進糞口進入第一池，池內糞便開始發酵分解、因比重不同糞液可自然分為三層，上層為糊狀糞皮，下層為塊狀或顆狀糞渣，中層為比較澄清的糞液。在上層糞皮和下層糞渣中含細菌和寄生蟲卵最多，中層含蟲卵最少，初步發酵的中層糞液經過糞管溢流至第二池，而將大部分未經充分發酵的糞皮和糞渣阻留在第一池內繼續發酵。流入第二他的糞液進一步發酵分解，蟲卵繼續下沉，病原體逐漸死亡，糞液得到進一步無害化，產生的糞皮和糞 厚度比第一池顯著減少。流人第三池的糞液一般已經腐熟，其中病菌和寄生蟲卵已基本殺滅。第三池功能主要起儲存已基本無害化的糞液作用。
Fresh feces enter the first tank from the fecal inlet. Feces in the tank begin to ferment and decompose. Due to different specific gravity, fecal liquid can be naturally divided into three layers, the upper layer is pasty fecal skin, the lower layer is massive or granular fecal residue, and the middle layer is relatively clear fecal liquid. The upper fecal skin and lower fecal residue contain the most bacterial and parasitic eggs, and the middle fecal residue contains the least insect eggs. The preliminarily fermented middle fecal liquid overflows to the second tank through the fecal pipe, and most of the fecal skin and fecal residue that have not been fully fermented are prevented from remaining in the first tank for further fermentation. The fecal fluid flowing into the second tank is further fermented and decomposed, the insect eggs continue to sink, the pathogens gradually die, the fecal fluid is further harmless, and the fecal skin and fecal thickness are significantly reduced compared with the first tank. The fecal liquid flowing into the third pool has generally been rotten, in which the bacteria and parasite eggs have been basically killed. The function of the third tank is mainly to store the basically harmless fecal liquid.