Dorney Lake Triathlon
Eton Dorney, United Kingdom · August · Independent (RunThrough / Human Race / others at Eton Dorney)
Course: 0.8 km (0.5 mi) swim, 19 km (11.8 mi) bike, 5 km (3.1 mi) run. 2024 pack: 19 km (11.8 mi); other listings 20 km (12.4 mi). 820 yd swim, 3.1 mi run.
Why people love it
- Calm, clear Olympic rowing lake with a simple 750 m (820 yd) rectangular swim.
- Dead flat, traffic-free tarmac with about 3 m (10 ft) of gain per lap.
- Sprint and first-timer formats suit a first race, including shorter super sprints.
- One transition and free on-site parking make for a simple day trip.
- Heathrow is about 12 km (7.5 mi) away.
Watch out for
- Open lake is exposed: expect a headwind on one side of each 5 km (3.1 mi) loop.
- Parking can be up to a 20-minute walk (about 1 km (0.6 mi) / 0.6 mi) to registration.
- No shade on the run; late waves run in midday heat.
- Distances vary by organiser and date: Standard bike is 38 or 40 km (23.6 or 24.9 mi).
- Changing rooms are not always provided, so arrive ready to race.
Race
How racers feel about it, how well it is run, and how it treats a first timer. Counts for 30% of the overall score.
Toughness: Moderate
- Racer satisfactionLoved3.9
Racers in 2014, 2017 and 2022 praised the clear water and flat course. Wind and a long food queue were the gripes. · Low confidence
- OrganizationWell run4.0
Smooth waves and efficient marshals in 2014 and 2017. A crowded start pen and slow post-race food queue were noted. · Medium confidence
- First timer friendlyIdeal first race4.6
One 750 m (820 yd) lap, flat closed bike and short run; shorter first-timer formats also run. · Medium confidence
Course traits, not part of the score
- PR potentialFast4.2
Flat and closed, with a 19 or 20 km (11.8 or 12.4 mi) bike that varies by date. · Medium confidence
Swim
Wetsuit odds, water temperature, calm, and the experience of the start. Counts for 16% of the overall score.
- Wetsuit legalUsually4.2
UK lake likely 17 to 21 °C (63 to 70 °F), well under the 24.6 °C (76.3 °F) limit. A hot spell could ban suits. · Low confidence
- Water temperatureComfortable3.6
Estimated 17 to 21 °C (63 to 70 °F), cool early and late in the season. Comfortable in a wetsuit. · Low confidence
- Calm waterGlassy4.6
Sheltered purpose-built rowing lake. Racers report calm, clear water, though wind can ripple the surface. · Medium confidence
- Swim easeVery easy4.6
Single 750 m (820 yd) rectangle with rope lane markers. · Medium confidence
- Swim experienceGreat3.9
Clean, clear water that one reviewer loved. Start pen can be crowded and the setting is functional, not scenic. · Medium confidence
- Swim supportGood4.0
Wave starts, a buoyed rectangle, rope lane markers and a thorough briefing. The start pen can be crowded. · Medium confidence
Bike
Road surface, closures, scenery and wind. Counts for 18% of the overall score.
- Road surfaceGood4.3
Smooth tarmac service road, wide enough for passing. One chicane to watch. · Medium confidence
- Road closuresFully closed4.8
Private, traffic-free venue road with no open traffic. · High confidence
- Bike sceneryPleasant2.9
Flat lakeside loops: pleasant in sun, but repetitive. · Medium confidence
- WindWindy2.3
Several racers call the lake extremely exposed, with a headwind on one side of each loop. · Medium confidence
Course traits, not part of the score
- Bike speedFast4.2
Fast and flat, with a headwind on one side of each loop. · Medium confidence
- Bike flatnessPancake flat4.8
Dead flat, about four 5 km (3.1 mi) laps. · High confidence
- Bike simplicityMostly simple4.0
Simple loops, though a left-right-left chicane after transition and being lapped by faster riders need care. · Medium confidence
Run
Crowds, aid stations, conditions underfoot and scenery. Counts for 13% of the overall score.
- Crowd supportDecent3.3
Spectators gather near transition and see riders about eight times. Quiet elsewhere. · Low confidence
- Aid stationsGood3.6
Drinks at the far and near turns of each run lap. No shortages reported. · Low confidence
- Run sceneryPleasant2.9
Out-and-back lakeside path with open views. · Low confidence
- Run conditionsEasy3.9
5 km (3.1 mi) on a flat path; short enough that missing shade matters less. · Low confidence
Course traits, not part of the score
- Run flatnessFlat4.8
Flat out-and-back over 5 km (3.1 mi). · Medium confidence
Conditions
Air temperature, how predictable the weather is, setting, and spectating. Counts for 13% of the overall score.
- Air temperaturePleasant3.9
UK summer highs are roughly 18 to 24 °C (64 to 75 °F). Estimated, and hot spells are possible. · Low confidence
- Weather reliabilityVariable3.1
Mostly dry UK summer, but one report was nearly windless and others describe strong wind. · Medium confidence
- Venue beautyPleasant3.3
Olympic rowing lake with trees and open views. Clean but functional. · Medium confidence
- Spectator friendlyEasy4.3
Compact venue where family can watch the swim, transition and loops from one place. · Medium confidence
Course traits, not part of the score
- Low altitudeSea level5.0
About 25 m (82 ft) above sea level. · High confidence
Stay and travel
Hotels, walkability, getting there, and the town around the race. Counts for 10% of the overall score.
- Hotel availabilityGood3.8
Windsor, Slough and Heathrow hotels are close. No sell-out problems found. · Low confidence
- Hotel valueNormal3.2
Windsor is pricey; rooms toward Slough and Heathrow are cheaper. · Low confidence
- WalkabilitySome driving3.2
Free parking is up to a 20-minute walk (about 1 km (0.6 mi) / 0.6 mi) from registration. Swim, transition and run are together. · Medium confidence
- Travel easeVery easy4.5
About 12 km (7.5 mi) from Heathrow and close to the M4 and M25. · High confidence
- LogisticsSimple4.2
One transition at the lake, race-day registration and free parking. Changing facilities vary by date. · Medium confidence
- Town and foodFine3.4
Eton and Windsor have good cafes and pubs a short drive away. Nothing on site beyond race food. · Low confidence
Key facts
- Location
- Eton Dorney, Buckinghamshire, United Kingdom
- Typical month
- August
- Latest or next date
- 3 October 2026
- Organiser
- Independent (RunThrough / Human Race / others at Eton Dorney)
- Field size
- About 1,500 athletes
- Distances (non-standard)
- 0.8 km (0.5 mi) swim, 19 km (11.8 mi) bike, 5 km (3.1 mi) run
- Swim venue
- Eton College Rowing Centre (Dorney Lake), 2012 Olympic rowing lake (lake)
- Water temperature
- 17–21 °C (63–70 °F)
- Wetsuit
- Optional
- Swim start
- wave
- Swim laps
- 1
- Bike climbing
- 3 m (10 ft)
- Bike laps
- 4
- Key climbs
- Small bridge on return side, about 3 m (10 ft)
- Run climbing
- 0 m (0 ft)
- Run shade
- None (open lake)
- Air temperature
- 14–24 °C (57–75 °F)
- Humidity
- Moderate
- Altitude
- 25 m (82 ft)
- Nearest airport
- London Heathrow (LHR), 12 km (7 mi) away
- Where to stay
- Windsor, Eton
- Booking
- Windsor, Slough and Eton hotels nearby; no race-week squeeze found.
What racers and reviewers say
- RacecheckRaced 2017 · aggregator · Positive
Rated 4.4 out of 5 and recommended. Loved the clear water and strict but efficient marshalling; quick registration; plentiful parking but about a 20-minute walk to the race centre. Bike fast and flat and humbling if lapped; run had no shade in midday heat and the post-race food queue was long.
“well organised”
- Alan Anna blogRaced 2014 · blog · Positive
British Sprint Championship age-group report. Calm clear water with rope lane markers for sighting, a flat traffic-free bike and a flat out-and-back run; conditions nearly windless. Praised the smooth running by Human Race with spaced waves and helpful marshals.
“a pretty good race”
- Steel City StridersRaced 2022 · blog · Positive
A first-time triathlete's club write-up of the season finale: first-class venue with calm water and a flat, fast bike and run. A first-timers option (200 m (656 ft) / 220 yd swim, 5.3 km (3.3 mi) / 3.3 mi bike, 2.5 km (1.6 mi) / 1.6 mi run) ran alongside the Olympic.
- RunThrough race information (2024)Raced 2024 · article · Positive
Organiser race pack: clockwise rectangular 750 m (820 yd) swim, anticlockwise 5 km (3.1 mi) bike laps, drinks at the far and near run turns, and a hard-standing car park near the boathouse with overflow up to a 20-minute walk away.
- 220 Triathlon evening seriesarticle · Mixed
Evening-series write-up (summarised from search snippet): wind took advantage of the open lake course and one rider called the bike a bit of a killer.
Show 2 more
- 220 Triathlon forumforum · Mixed
Racers describe a dead flat loop with a headwind on one side and a tailwind on the other; warn about the left-right-left chicane after leaving transition. One mentions about a quarter mile walk from car park to transition.
- Addiscombe forumforum · Mixed
Club thread (snippet only, page had errors): a duathlon report calls the lake extremely exposed with head wind then tail wind on out-and-back loops; a women-only event report found the bike pretty awful in the wind.
Raced Dorney Lake Triathlon? Your notes on the course, conditions and logistics help the next athlete decide.
Sources
Pages we used for facts and ratings. See how we rate.
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