I first heard of sitz bath after giving birth Joint Pain Hack Review to my 4th baby, Elisha. My ob had to perform an episiotomy since she was a bit big (at 3.2 kilos) for me. The nurse would come a few 2-3 times a day to give me a bath - dipping me in a tub waist down. It relieved the pain and from what my nurse told me, it would help heal the cut and suture of the peritoneum faster.
Sitz literally means to sit (from the German word sitzen). Sitting down in a tub while bathing is maybe the reason why it was named as such. Some people use baking soda or salt to treat hemorrhoids and anal fistulae; women suffering from menstrual cramps or had a recent episiotomy also takes this kind of bath. This may also reduce discomfort due to inflammation of the prostate gland.
The bathtub used is a plastic or ceramic tub that can be placed over the toilet and filled with water. Sitting in the bathtub for 15 - 20 minutes is recommended to patients. One can take it in a regular bathtub, but the patient's feet needs to be kept over the side of the tub or put in the water, while the knees are kept bent. This may not be quite as hygienic when taking it in a sitz bathtub since constant flow of warm water into the bath is needed. Sitting in warm water allows healing and relief from pain because it reaches the impacted area. It uses the basis of water or hydro therapy. If you believe in the saying "water is life", then this is one of the many things that water can do.