There is an italian saying regarding how much salt to add to a pot of water for pasta. “As salty as the sea”. I am going to take a moment to step in front of that saying and talk about science. Actual seawater usually has a total dissolved solids concentration of about 35,000 mg/L. This means that all of the dissolved ions (a large majority being chloride and sodium ions, which comprise table salt), have a concentration of 35,000 parts per million. This means that sea water is 3.5% salt. This is at the very high end of the salty tasting scale, and the reason why seawater is too salty to drink. It is simply too much salt for us and our kidneys.
The human tongue is very sensitive to salt, and the water will actually start to taste as salty as the sea much sooner than it will actually be as salty as the sea.
Studies on Taste and Odor. Several studies are available on the taste threshold of sodium chloride in drinking water. It is not possible to identify precise threshold values for the taste of sodium in drinking water because detectable concentrations vary among individuals and for the same individuals at different times. Age and health status also impact a person’s ability to detect the taste of sodium. Other factors affecting taste of sodium in drinking water include possible masking by other dissolved substances, water temperature, and the anion forming the salt. The average taste threshold for sodium in water at room temperature differs substantially among individuals and ranges from about 30 mg/L to 460 mg/L. Sodium in water does not by itself cause odor problems. The World Health Organization has established a drinking water guideline of 200 mg of sodium/L on the basis of esthetic considerations (i.e., taste). When sodium chloride is dissolved in distilled water, it is possible to detect the overall impact on taste prior to recognition of the taste as salty.
https://www.epa.gov/sites/production/files/2014-09/documents/support\_cc1\_sodium\_dwreport.pdf
For pasta, it will be 8 to 10 grams of coarse salt (1 scant tablespoon of Diamond Crystal; about 2 teaspoons of Morton’s) for every 1 liter (quart) of water should do the trick. I cook a full batch of fresh pasta or a 1-pound box of dried pasta in 5 quarts of water, give or take, so there’s plenty of room to tumble and expand (no need to measure; fill an 8-quart stockpot two-thirds of the way). Ultimately, you’re using about a palmful of salt, but don’t let that scare you; the pasta only absorbs a fraction of it. Use whatever coarse salt you prefer; over time, adding the right amount will become muscle memory.