Water Quality Testing for Triathlons

Water Quality & Testing Guidance

Triathlon events in the UK are required to ensure the water is safe for participants prior to its use, under the BTF event organiser rules.

There are several ways for organisers to meet this requirement, such as:

  • Testing of the water
  • Obtaining data from external water testing (EA Bathing Sites testing)
  • Existing tests from venue / landowners

Often triathlon event organisers perform their own testing, either because other available data is too old, or not close enough to the event date, or because sample locations are not close enough to the location of the planned swim, to be relied upon.

Triathlon Open Water Swimming – What to test for?

There are three elements that need to be tested / checked for:

  • E.coli
  • Enterococci
  • Blue-green algae
ParameterInland WatersCoastal Waters
E.coli< 500 cfu / 100ml< 200 cfu / 100ml
Enterococci< 200 cfu / 100ml< 100 cfu / 100ml
Blue-green algae< 100,000 cells / ml

cfu = Colony forming unit
The above thresholds are aligned to the EU Bathing Water Standards / World Heath Organisation thresholds.

When should I test?

British Triathlon provides guidance to organisers when considering when to test their water body. For water bodies that are not regularly used for other open water swimming activity, and where testing needs to be organised, British Triathlon suggests the following testing regime:

Test 1: One month prior to the event – to give an early indication of any problems and provide sufficient time for contingency plans to be developed.

Test 2: Two weeks prior to the event – to give an indication of whether the water quality has improved or worsened.

Test 3: One week prior to the event – to inform the final decision for the swim to take place and allow sufficient time to implement contingency and inform participants (NOTE: It takes 48-72 hours for bacterial results to be produced).

This may be able to be refined when a venue is used regularly, or where there is historical data that can demonstrate the water body is generally not affected by sudden changes to water quality.

Where should I take my tests from?

You want to test as close to where your participants will be swimming, as possible. A suggestion is to test along your swim course at the start, middle and furthest points.  This provides a good indication of the water quality across the swim course.

The benefit of taking multiple tests is that, in the event of a failure, you may be able to establish the potential source of the bacteria (e.g. a stream running into the lake) or have options to re-locate your course in the event of high levels of bacteria in a particular location.

How do I take my tests?

Ideally, water samples want to be collected from the swim course and at approx. elbow depth (30cm) below the surface. This means the sample being analysed is reflective of area of the water being swum in by your participants.

That may mean getting out on the water in a boat, on a canoe, kayak or paddleboard if possible.

Taking samples from the edge of a water body is acceptable and may often be the only option – but try to avoid areas of stagnant water (unless that’s where you plan to swim) or with large amounts of surface scum, debris or mud – as this can skew your results (and sometimes mean they cannot be analysed).

Triathlons & Blue-Green Algae

British Triathlon organiser rules require levels of blue-green algae to be less than 100,000 cells per ml, which is aligned to the World Health Organisation guidelines.

Algae is present in many water bodies, and there are hundreds of types. Only a small number of ‘blue-green’ algae are potentially harmful to swimmers, and only when forming on the surface in blooms or scums.

If there’s signs of blue green algae, testing is important as it not only identifies the type of algae, and therefore whether it’s potentially toxic or not, but also the levels.

Algae levels can change very quickly – both increasing and decreasing. Knowing the levels of algae, through blue green algae testing, and where that sits within the World Heath Organisation thresholds is important. Both for the safety and wellbeing of your participants but also to help reduce the chance of events being cancelled unnecessarily.

water quality testing for wild swimming lakes
water quality results certificate

Results within 72hrs

Our service provides fast accredited lab analysis of water samples, with results normally returned within 72hrs.

results analysis certificate

Traffic light certificates

Clear and concise results – colour coded and aligned to the EU Bathing Standards and/or British Triathlon guidelines.

Complete water testing kit

Our water testing kits contain everything you need for your test – including full instructions, sterile bottles and return packaging.

Get in touch – we’re happy to help

If you’re unsure about what you need to test for, and when – then do get in touch. It’s not an exact science, but we can help with some expert industry advice to help advise on what may be a reasonable and appropriate level of testing prior to your event.

We’ve been advising triathlon event organisers for over 10 years on their water quality testing requirements, and take an operational and pragmatic approach.

Our Water Quality Testing Service


Easy to order & hassle free


Kits include full instructions & return packaging


Fast lab analysis - results within 72hrs


Easy to understand certificates - no jargon

We make water quality testing simple and hassle free, backed up by industry leading expert advice and support.

Fast, reliable & hassle-free open water quality testing

Swim Safety provides water quality testing and analysis services for a large number of event organisers, venue operators, festivals, wild swimming groups, fire services, councils & local authorities, TV & film productions, and private landowners in the UK.

One of the key challenges for event organisers & venue operators is that it can often be very difficult to organise one-off or irregular water sampling at a reasonable cost.

Furthermore, many of the results that are returned consist only of raw data, with little or no interpretation.