Every number on SofterTap comes from a named source or from a calculation you can repeat. This page explains where our figures come from, how the calculators work and how we keep them up to date.
Who runs SofterTap
SofterTap is written and maintained by Daniel Moreno. He is not a plumber, a water treatment professional or a chemist, and the site doesn’t claim lab tests or hands-on product trials. What it offers is careful reading of official documents, open calculations and tools that let you use your own numbers.
Where the figures come from
| Figure | Source |
|---|---|
| Hardness of a city’s water | The water utility’s own annual water quality report (Consumer Confidence Report) or its official water quality page |
| Hardness classes (soft to very hard) | U.S. Geological Survey |
| Indoor water use per person | U.S. Geological Survey (80–100 gallons a day) |
| Softener salt and water efficiency | NSF/ANSI 44 efficiency rating, as summarized by the PNNL Building America Solution Center |
| Capacity at different salt doses, iron allowance | Manufacturer manuals, named in each article |
| Prices (for example, a bag of salt) | A named retailer, with the date we checked it |
How we convert hardness units
All conversions go through milligrams per liter of calcium carbonate (mg/L as CaCO3), using exact unit definitions rather than rounded rules of thumb.
| Unit | mg/L as CaCO3 | Derived from |
|---|---|---|
| 1 grain per US gallon (gpg) | 17.118 | 64.79891 mg per grain ÷ 3.785411784 L per gallon |
| 1 Clark degree (°e) | 14.254 | 1 grain per imperial gallon (4.54609 L) |
| 1 German degree (°dH) | 17.848 | 10 mg/L CaO × 100.09 ÷ 56.08 |
| 1 French degree (°f) | 10 | 10 mg/L CaCO3 |
| 1 mmol/L | 100.09 | Molar mass of CaCO3 |
How the calculators work
The softener size calculator multiplies people × gallons per person × hardness to get grains removed per day, then multiplies by the days between regenerations. The salt calculator divides a year of grains by the softener’s efficiency in grains per pound of salt. Each tool page shows its full formula and a worked example.
The calculators run entirely in your browser. Nothing you type is stored or sent anywhere.
Before we publish a table or a calculator, we check its results against a separate calculation written in another programming language. The tables in our articles are generated from the same formulas as the tools, so the numbers match across the site.
How we keep figures current
- US utilities must publish their water quality report by July 1 each year. We review the city figures each summer and update the date on each page.
- Prices are rechecked at least once a year and always show the date we checked them.
- Before publishing, we open every external link. If an official page disappears, we link to an archived copy and say so.
What we don’t do
- We don’t give medical or drinking-water safety advice. For questions about the safety of your water, contact your utility or your state drinking water program.
- We don’t publish a city’s hardness until we have read it in that utility’s own document.
- We don’t invent test results, reviews or testimonials.
Corrections
If you spot an error or an outdated figure, email hello@softertap.com with the page and, if you can, a link to the newer source. We fix confirmed errors and update the “last updated” date.
