What to stock. How to store it.

A consumable is anything you use up and buy again: a treatment chemical, a box of test strips, a replacement gasket. The hard questions are always the same ones, so every guide answers them in the same order.

• How much to keep, in plain terms, for one person and for a household.
• How long it lasts, and how to tell when it has quietly gone past its useful life.
• How to store it safely, so it works the day you reach for it.
• What to buy, with an honest price range and a note on when the cheap version is fine.

Nobody pays to be listed here. When a product is genuinely worth the extra money we say so, and when the generic does the same job we say that too. Where a guide touches safety, the dosing and handling are checked against the EPA, CDC, FDA, or the relevant primary source, with those references on the page.