These test strips are a simple method of keeping an eye on the chemical levels of the pool water. It is essential that your pool water is tested on a regular basis to help keep an eye on any germs or nasty bacteria & to make sure that the chemical balance is correct to stop skin irritations. To test the pool water is plain & simple to do by dipping one of the strips into the water & removing quickly. Holding it horizontally you can check the results on the coloured chart that is printed on the container. These test strips will also indicate the waters p H & Alkaline levels, each strip has three sections helping to identify the individual levels. The recommended levels for the chemicals in your pool water are for the Chlorine that should be between 13ppm, the p H levels are between 7.27.6 & the total Alkalinity levels should be between 80100 or 100120ppm, this all depends of the type of chemical solutions that has been used to treat your pool. All warnings & instructions must be adhered to, which are clearly labelled on the packaging.