The 75 Hard water rule: one US gallon of plain water per day — 128 oz, or roughly 3.78 liters. Not coffee, not tea, not sparkling water, not electrolyte mix. Plain water, finished before midnight, 75 days in a row. It sounds like the easiest rule; it's the one that quietly kills the most days, because it's the only task you can be "80% done" with at 10 PM and still fail.
How Much Is a Gallon, Really?
| Container | Refills for 1 gallon |
|---|---|
| Standard 16.9 oz bottle | 7.5 bottles |
| 32 oz (1 quart) bottle | 4 refills |
| 40 oz tumbler | 3.2 refills |
| 64 oz half-gallon jug | 2 refills |
| One-gallon jug | 1 — the visual cue that works best |
Most finishers land on either a single gallon jug (progress is visible all day) or a 32 oz bottle with a "4 refills" rhythm tied to meals.
The Hourly Pacing Schedule
| Time | Drink | Running total |
|---|---|---|
| On waking | 16 oz before coffee | 16 oz |
| Breakfast | 16 oz | 32 oz |
| Mid-morning | 16 oz at your desk | 48 oz |
| Lunch | 16 oz | 64 oz — halfway by noon ✓ |
| Afternoon | 16 oz | 80 oz |
| Pre-workout #2 | 16 oz | 96 oz |
| Dinner | 16 oz | 112 oz |
| ~2h before bed | Final 16 oz | 128 oz ✓ done |
The halfway-by-noon rule: if 64 oz aren't gone by lunch, tonight is a chug-and-suffer night. Front-loading is the entire strategy — evenings belong to your second workout, dinner, reading and photo, not 40 oz of water.
What Counts Toward the Gallon (and What Doesn't)
- ✓ Plain water — still, from any source, any temperature.
- ✗ Coffee and tea — allowed to drink, never counted. (Full drink rules here.)
- ✗ Sparkling or flavored water — purist reading of the rules says plain only; don't gamble your restart on bubbles.
- ✗ Electrolyte mixes and protein shakes — fine for your diet, separate from the gallon.
A Quick Safety Note
Spread across a day, a gallon is reasonable for most healthy adults training twice daily — but don't slam huge volumes in one sitting to save a failed day; extreme rapid intake can cause hyponatremia (water intoxication). Salt your food normally, and if you have kidney or heart issues, clear the gallon with your doctor before Day 1 (see the Cleveland Clinic's take on the program's demands).
Tracking the gallon in the 75 Hard app
- "1 Gallon of water" is a core checklist task — tap it green when the jug's empty.
- The home-screen widget shows the task still pending all day — a glanceable nudge that beats any reminder app.
- Check it off at the final glass, not from memory at midnight — the one-tap flow makes real-time honesty effortless.
- Spot your weak days on the calendar: if water is what keeps going red, move your refill schedule earlier.
128 oz a Day Needs a Visible Scoreboard
Free 75 Hard tracker for iPhone — water, workouts, diet, reading and photo, one tap each.
Download 75 Hard — Workout Challenge75 Hard Water: FAQ
How much water is required?
One US gallon — 128 oz / 3.78 L — of plain water daily, one of the five official 75 Hard rules.
Does coffee count toward the gallon?
No. Nothing but plain water counts.
Can I drink it all at once?
Don't — pace it. Rapid massive intake is risky and miserable; the schedule above makes the gallon almost automatic.
Is a gallon a day safe?
Generally yes for healthy adults when spread out, particularly with two daily workouts. Medical conditions? Ask your doctor first.