Hydration for tween (ages 12-13) doing swimming
EFSA total-water baseline for ages 9-13 is 2,100 ml/day for boys and 1,900 ml/day for girls, plus extra fluid on training days. Swimmers lose fluid through sweat and respiration even in the pool — but because they don't feel sweaty, they drink dramatically less than field athletes.
Quick answer
Hydration for tween (ages 12-13) doing swimming
Per EFSA's 2010 Dietary Reference Values, the total-water Adequate Intake (food plus beverages) for ages 9-13 is 2,100 ml/day for boys and 1,900 ml/day for girls. On swim-training days, add fluid on top of that baseline to replace sweat loss, calibrating the extra by weighing before and after the session.
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Tweens (ages 12-13) doing swim training face a different hydration problem than either the general age group or the general sport. Swimmers lose fluid through sweat and respiration even in the pool — but because they don't feel sweaty, they drink dramatically less than field athletes. Pool-side fluid loss is invisible — swimmers are cooled by the water, don't feel thirsty, and exit a hard set already hypohydrated. Humidity over the pool surface adds respiratory loss. Sessions and matches are at full duration; travel teams and club-level intensity begin in this band. Start from the EFSA total-water baseline for ages 9-13 — 2,100 ml/day for boys and 1,900 ml/day for girls (food plus all beverages) — then add fluid on top of that to cover the session's sweat loss.
Targets for tweens (ages 12-13) doing swim training
Start from the EFSA total-water baseline, then add for training
EFSA's total-water Adequate Intake for ages 9-13 is 2,100 ml/day for boys and 1,900 ml/day for girls (water from food plus all beverages, at moderate temperature and activity). Swim training adds fluid on top to replace sweat loss; calibrate the exact amount by weighing pre/post.
Source: EFSA 2010 Water DRV + individualized sweat-rate assessment
Pre / during / post — the only framework that matters
Start the session ahead, not catching up. For this age band and sport: a pre-session dose 60-90 minutes before, scheduled sips during, and weight-based replacement after. Non-training days use the age-band baseline only — don't over-drink on rest days.
Urine colour is the cleanest daily signal
Pale straw by the mid-afternoon bathroom visit means the athlete started the session hydrated. Dark yellow or amber before training means a pre-session 500 ml top-up, not 'just start'.
Age maturity: Sessions and matches are at full duration; travel teams and club-level intensity begin in this band.
Match intake to real session length. A preschooler's 'soccer practice' is structurally different from a teen's — don't apply teen protocols to 5-year-olds, and don't apply preschool protocols to competitive tweens.
Practical tips for this age and sport
- Bring a labelled bottle to the pool deck — every single session
- Between sets: 100-150 ml — set it as part of the athlete's recovery ritual
- After any session >30 minutes: 400 ml within 20 minutes of exiting the pool
- Chlorine can suppress thirst — don't rely on 'do I feel thirsty' during a swim
- Tournament weekends: per-match bottle + between-match bottle — non-negotiable
- Electrolyte drink for any single session over 60 minutes at moderate-to-high intensity
Training-day plan — printable for the sports bag
Enter the athlete's age, weight, and sport. Get a pre/during/post schedule, a bottle-size recommendation, and a 7-day tracker for training weeks. Free, no signup to download.
Build the training plan →When to watch or act
Signs of Dehydration
- Dizziness on standing after a hard set — immediate stop, 500 ml, no return without clearance
- Urine darker than light straw before training — pre-session deficit, top up 500 ml before starting
- Performance drop in the last third of the session — classic hydration signal, not 'being tired'
- Headache or nausea during or after training — stop, hydrate, don't push through
Sources & Citations
- 2100 mL/day (2.1 L/day) — EFSA total-water Adequate Intake for boys 9-13 years (includes water from food plus beverages)[1]
- 1900 mL/day (1.9 L/day) — EFSA total-water Adequate Intake for girls 9-13 years[1]
- 2% or more body-mass loss — Physical performance declines at as little as 2% body-mass loss; >=2% impairs thermoregulation, cardiovascular function and aerobic exercise[2]
- Ucol 1-3 = well hydrated — Urine color 1-3 on the Armstrong 8-point chart indicates euhydration (well hydrated); 4 or higher signals the need for fluids[3]
- 4-8% carbohydrate + 400-1100 mg/L sodium — Optimal sports-drink composition for sessions over 60 min (plain water supplies neither carbohydrate nor sodium)[4]
- [1]EFSA 2010 Water DRV — EFSA Panel on Dietetic Products, Nutrition, and Allergies (NDA). Scientific Opinion on Dietary Reference Values for water. EFSA Journal. 2010;8(3):1459.DOI: 10.2903/j.efsa.2010.1459
- [2]Popkin 2010 — Popkin BM, D'Anci KE, Rosenberg IH. Water, hydration, and health. Nutr Rev. 2010;68(8):439-458.PMID: 20646222DOI: 10.1111/j.1753-4887.2010.00304.x
- [3]HPRC (US DoD) — Human Performance Resources by CHAMP (HPRC), Uniformed Services University / US Department of Defense. How to Accurately Assess Hydration Status Using Urine Color Charts.
- [4]Mosler et al. 2020 DGE Position — Mosler S, Braun H, Carlsohn A, et al. Fluid Replacement in Sports: Position of the Working Group Sports Nutrition of the German Nutrition Society (DGE). Dtsch Z Sportmed. 2020;71(7-8-9):178-184.DOI: 10.5960/dzsm.2020.453
Last reviewed: 2026-06-22. Every figure on this page is sourced to the named primary references above.
Frequently Asked Questions
How much water does a tween kid need on a swim training day?
Start from the EFSA total-water baseline for ages 9-13 — 2,100 ml/day for boys and 1,900 ml/day for girls, counting water from food plus all beverages — then add fluid on top to replace what the session sweats out. Calibrate the extra by weighing before and after training.
What's the pre / during / post split for this age and sport?
Pre 400-500 ml in the 90 minutes before, during 200 ml every 15-20 minutes, post 500-600 ml within 30 minutes. Electrolyte drink if the session runs over 60 minutes.
What about sports drinks — does swim training need them at this age?
For sessions or matches over 60 minutes at moderate-to-high intensity, yes. Otherwise water + a balanced post-session meal is better than a sports drink with added sugar.
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