Marathon Hydration Plan: Water Stops, Cups and Carrying a Bottle

One cup every water stop sounds like a marathon hydration plan until you ask how far apart the stops are.

At 10 minutes per mile, stations two miles apart arrive every 20 minutes. If you actually swallow 100ml from each cup, one cup per stop gives you 300ml over a representative hour. Two cups give 600ml. Neither number tells us what you need.

A useful plan starts with your practiced fluid needs, then checks whether the course can supply them. Below is the map-and-cup arithmetic I'd do before deciding whether to carry a bottle. The examples are made up for planning, not fluid prescriptions.

Start with your training notes

NATA's fluid-replacement position statement recommends individual plans and avoiding body-weight gain from overdrinking. When sweat rate is unknown, drinking to thirst is a safer fallback than forcing an hourly volume. And a planned range still needs adjustment for conditions and tolerance.

If you have time before the race, use the sweat-rate test during suitable training sessions. Baker's review of sweat testing explains why conditions, effort, body size, and measurement methods matter. A result from one cool run isn't a permanent number stamped on your forehead.

And a smaller runner, including a woman, shouldn't inherit a larger runner's bottle schedule. Use your own observations rather than a fixed sex-based discount.

Write down the amount you drank on comparable runs, how it felt, and the conditions. If you're repeatedly struggling with hydration or have had a race medical problem, work through the plan with a qualified clinician or sports dietitian. Course math can organize an appropriate plan; it can't choose one medically.

Read the course guide with your pace beside it

Find the current event guide and map. Last year's race report is a useful clue, but it doesn't confirm this year's supplies.

I'd put these details on one sheet:

• Water locations, including the first station and the longest gap.
• Which stations also offer sports drink, and the specific product if published.
• Whether the race describes cups, bottles, refill access, or carrying restrictions.
• Your expected time between stops, including slower late miles.
• Where a bottle or familiar backup would solve a genuine access problem.

Unclear information stays unclear. And don't assume a table has a refill tap because it has water cups, or that every station carries the same drink.

The calculation is short: gap in miles × pace in minutes per mile = minutes between stations. Keep the distance and pace units matched. A kilometer map needs minutes per kilometer.

At 12 minutes per mile, that same two-mile gap takes 24 minutes. A missed stop could leave four miles between successful pickups, or 48 minutes at that pace. Check that gap before race morning, while the answer can still influence what you carry.

Need a starting plan to bring to your course map? Build your carb, fluid, and sodium timeline in about 60 seconds: Use the free EnduranceOS planner.

Count the part of the cup that reaches you

A cup's capacity and the amount you swallow are different numbers. Some stays in the cup. Some goes down your shirt. Water poured over your head doesn't belong in the drinking total.

Practice with a measured amount in a paper cup somewhere safe. Try your normal running pace and a brief walk, then estimate what you swallowed after allowing for leftovers and spills. It won't be laboratory-perfect, but it beats giving your shirt credit for drinking.

For the table below, assume 100ml actually swallowed per cup. The spacing, pace and cup amount are hypothetical. The hourly figures describe a repeating pattern, not a claim that every individual race hour contains exactly that many stations.

Pace	Station spacing	Time between stops	One 100ml cup per stop	Two 100ml cups per stop
10 min/mile	1 mile	10 minutes	600ml/hr	1,200ml/hr
10 min/mile	2 miles	20 minutes	300ml/hr	600ml/hr
12 min/mile	2 miles	24 minutes	250ml/hr	500ml/hr

So that first row is why “two cups at every station” deserves a second look. The course offers opportunities, not instructions to drink all of them.

To check your own pattern, divide 60 by the minutes between stops, then multiply by the volume swallowed per stop. For the final row, 60 ÷ 24 × 100 = 250ml/hr. Drinking two cups doubles the swallowed volume, assuming the second cup is equally successful.

But don't multiply that representative rate straight into a precise whole-marathon total. The distance to the first station, the finish after the last station, changing pace, skipped pickups and partial hours all matter. For a total, list the actual pickups on the map and add those volumes.

Decide what a bottle would actually solve

My preference would be the lightest setup that reliably supports the practiced plan. Sometimes that's course water. Sometimes it's a flask that stops one long gap from becoming the day's main topic.

A bottle gives you access between stations and control over what it contains. It also means carrying it, opening it, and finding an allowed way to refill it if needed. And test the full bottle in the actual belt, vest or hand position. A setup that feels fine in the kitchen may spend the first mile punching your ribs.

Suppose a runner has practiced 500ml/hr in comparable conditions and expects a 30-minute stretch without access. That portion of their plan represents 250ml. This is a supply calculation for that hypothetical runner, not a reason for everyone to drink 250ml before the next table.

Write down the next reliable access point and what happens if you miss it. But don't build the backup around chugging twice as much at the following stop. Ease off, reassess thirst and conditions, and use available support rather than forcing a catch-up volume. If access cannot support your needs safely, the plan needs changing before the start.

Sports drink goes in more than one column

Water and sports drink both count as fluid. Sports drink may also supply carbs and sodium, so changing the number of cups changes the fuel calculation too.

For a hypothetical label containing 6g of carbs and 60mg of sodium per 100ml, swallowing 300ml supplies 18g of carbs and 180mg of sodium. At 600ml, it supplies 36g and 360mg. Those are assumed label values, not specifications for your race's drink or a recommended intake.

So use the actual product and mixing information when available, and leave uncertainty in the plan when cup fills or dilution aren't known. An electrolyte drink with no carbohydrate won't replace a gel just because both came from the aid station.

What about water with gels? Follow the directions for your specific product and keep the whole-race fluid plan separate. GU, SiS and Maurten packets don't all have identical instructions. The marathon gel guide covers those differences and how drink carbs change the packet count.

And sodium doesn't make excessive drinking safe. The hyponatremia guide explains why another salt capsule isn't permission to keep taking cups.

Put the plan on one page, then rehearse it

Here's the worksheet I'd keep with the race map:

Planning item	Your note
Practiced fluid range and conditions	Amount consumed, effort, weather, tolerance
Reliable access	First stop, longest gap, last stop, refill rules
Cup estimate	Volume actually swallowed in practice
Pickup pattern	Planned opportunities, adjusted for thirst and conditions
Carried supply	Bottle size, contents, and where it can be refilled
Food and drink totals	Carbs and sodium from everything actually consumed
Missed-stop option	Next access, carried reserve, and when to seek support

Rehearse the cup or bottle handling alongside your fuel, then check the forecast and current event guidance before race day. But a warmer forecast doesn't create one automatic percentage increase in water or salt. It may change your pace, cooling needs and access plan as well.

NATA warns that dehydration and overhydration symptoms can overlap. Confusion, a severe or worsening headache, repeated vomiting, or difficulty breathing calls for race medical help. Don't diagnose the problem by guessing whether more water, salt or a gel will fix it.

The marathon nutrition guide connects this to breakfast and fuel timing. Your water-stop sheet handles the part between “I have a target” and actually drinking it. Do that homework before mile 20, while changing the carrying setup is still an option.

The EnduranceOS planner builds an hourly carb, fluid, and sodium plan in about 60 seconds. It's free. Put that starting plan beside your training notes and course map, then make sure the cups and bottles can do their part.

This article is educational, not individual medical advice. Conditions or medications affecting fluid balance, previous hydration emergencies, or recurring symptoms call for guidance from a qualified clinician.