The primary therapeutic factor at the resort is the mineral water.

The mineral water at Stara Zagora Mineral Baths springs from a depth of 1600 meters.

Its physicochemical characteristics classify it as slightly mineralized, hyperthermal water with a neutral reaction (pH 6.9, due to the presence of 60 mg of carbon dioxide).

The temperature at which the water surfaces is approximately 40 ˚C, with a flow rate of 20 liters per second.

The water at Starozagorski Mineral Baths treats:

All neuralgic conditions;
 All rheumatic conditions;
Inflammations of the sciatic nerve;
Inflammations of the female pelvic organs;
Inflammations of the urinary system, kidneys, and bladder;
 Sand in the kidneys and bile ducts;
Jaundice;
Gout.

The water contains traces of:

lithium ion, magnesium ion, strontium ion, boron ion, and iodine ion;
nitric and phosphoric acid.