How to test the quality of Open Water for bathing or swimming

Customers often ask us how they can determine the suitability and monitor the quality of open water (lakes, rivers etc.) for bathing or swimming. Some people may have a lake on their private property and want to make sure it is safe for swimming; or they may live near open water where swimming can take place.

Testing open waters before you bathe or swim is important to make sure that you do not put yourself or others at risk from illnesses.

The World Health Organisation (WHO) has published general guidelines. The European Union (EU) has also created a directive concerning the management of bathing water quality; it includes guidelines that all bathing water in the EU (including the UK) should meet. Swimming in inland water in the UK is regulated by the Bathing Water Regulations 1991 & 2013.
The EU directive and UK Bathing Water Regulations 1991 & 2013 are aimed primarily at those looking to offer their open water to the general public. Both are however a great source to give an insight into what is deemed acceptable water quality for people to swim in.

Below we have put together a general summary of the guidelines in the United Kingdom (UK), which follows similar guidelines to the EU. In addition to this, please make sure that you always check your local guidelines to make sure that everyone is safe. . If you plan to open your water to the general public you must strictly adhere to the guidelines set by the EU and UK, therefore please refer to the official guidelines. (Please note, our recommendations are only suggestions on what tests to do and how often to test the water).

How often should I check the water: It is recommended to check the quality of the water a number of times throughout the year, ideally before the start of the bathing season, every 4 weeks as well as at the end of the bathing season.

Parameter Value Maximum Bathing Water Regs
Total Coliforms, cfu per 100ml low
E.Coli, cfu per 100ml 1,000*
Intestinal enterococci, cfu per 100ml 400*
pH 6 to 9
Appearance No abnormal change in colour
Odour None
Transparency >1 metre
Surfactants No lasting foam
Mineral Oils No surface film or odour
Phenols No phenolic odour
Blue-green algae, cells per litre If visible bloom, count should be carried out

*Recommended levels to receive standard "good".

Recommended Tests:

To test water for public use a laboratory test is recommended. The results of the bacteria laboratory test are available within 4-10 days and are presented in cfu/100ml. Here is a selection of relevant tests from our UKAS approved laboratory:

For the full range of laboratory tests, please click here. If you are planning on carrying out various or regular tests, then please contact us for a specific quote.

We also offer a range of field test kits which provide instant results. Below is a selection of products:

Inland water:

You might also decide to test for additional parameters:

  • Nitrate/Nitrite - this is particularly important if your open water is on or near farmland
  • 5-in-One to test pH, Total Alkalinity, Nitrate, Nitrite and Total Hardness
  • Total Metals 


Sea water: This resource has primarily been created for people wanted to check water quality of inland waters, like lakes & rivers. Whilst the regulations may also cover sea water, our test strips & bacteria tests are not suitable to check salty sea water. To test marine/salt water, please use our iDip 570 Photometer for marine/salt water.

Swimming Pools & Spas: These guidelines are designed to give general information about regulations for open water swimming. This includes lakes, rivers etc. Different recommendations exist for swimming pools & spas - please refer to separate guidelines for these. Click here for our wide range of test strips for Pools & Spas. The iDip photometer Pool & Spa is ideal for regular testing of public pools and commcercial use.


Further Free Resources:

Got a question about water testing? Try our complete list of Free Water Testing Resources. Here are the most frequently read guides:

If you can't find what you are looking for then please contact us, as we can source many other test kits. Discounts for bulk purchases available, please contact us to find out more.

Disclaimer: Only opinions based upon our own personal experience or information detailed in academic journals or other publications is cited. This has been done exclusively for anyone who is interested in this subject but is not intended to replace proper analysis. We cannot accept responsibility and liability of any kind which may result from the application of this information. We always recommend to consult an expert to discuss any test results or get a full recommendation on the specific subject and specific to your situation by an expert.

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