How to clean pool limescale

Posted on Friday, 4 March 2022

If you have limescale in your pool, discover our professional tips on what steps to take to resolve this problem

Limescale in swimming pools is one of the most stubborn and difficult issues to deal with for those having to look after a swimming pool or hot tub. This is due to the build-up of calcium chloride. It speeds up the deterioration of the pool’s lining, as well as irritating the skin, eyes, and mucus of swimmers. To find out how to tackle this problem, it is important to have specialist advise from professional experts, such as those at CTX.

In pools, we often find limescale build-up on metallic components under the water, as well as on the cleaning systems and the heating equipment. In general, limescale build-up can first be identified by a white foam appearing at the edge of the pool. This foam solidifies over time, and once this happens, it becomes much more difficult to remove, which is when descaling agents need to be used. 


The damage caused by limescale can include: blocked pipes, corroded walls, blocked filters, etc. It is a problem that should not be underestimated or  undervalued. 


The formation of limescale is due to the presence of three salt minerals in the water, calcium silicate, calcium carbonate, and magnesium. 


There are various causes of limescale build-up:

  • Excessively hard water. Water is hard when it contains too much lime. The hardness or softness of the water, or the higher or lower proportion of lime in the water can also depend on our geographic location.

  • Water evaporation, which tends to leave a limescale line on the pool.

  • Excessively high pH levels. This is the main cause of limescale in a pool. To prevent this, frequent and regular measurements need to be taken of how hard or soft the water is, as well as its pH levels.

How to resolve the limescale problems in pools

To resolve the issue of calcium chloride and magnesium build-up in our pool, we need to carry out a series of tasks with specialist tools and products, all of which are included in the CTX catalogue.


Firstly, to know how to clean limescale in our pool, we need to analyse different parameters of the pool water, mainly the pH levels, alkalinity, chlorine levels, and how hard the water is. Among the CTX tools available to analyse the pool water, are the following:

  • Analysing kits. For example, the CTX analysing kits with liquid have two reactive agents, OTO (orthotolidine) to determine the levels of any disinfectants, and phenol red to determine the pH levels. There are also the Pooltester Kits, which provide a quick result  by mixing the sample water and the reactive tablets. The Checkit comparison tool, a compact, easy to use, colorimetry device. Minikits, quick tests with a high accuracy rate. The Oxy-Active Liquid Analyser, used to analyse the waste levels of this disinfectant.

  • A wide range of analysis strips, with reactive agents that allow users to measure using contrast ratio. CTX offers three, four, and up to seven different parameters, allowing the presence of chlorine, phosphates (a primary component of algae), bromine, chloride, biguanides, peroxide, and pH levels, etc. to be determined. The overall alkalinity of the water can also be measured.

  • Reactive agent. Colorimetry that includes these components reacting when coming into contact with the water, changing colour and providing us with a readable result.

  • Photometers. These are multifunctional tools to analyse different parameters, including pH levels, and total alkalinity levels, with a high degree of accuracy and reliability.


Next, we have to adjust the water’s pH and alkalinity levels. The pH needs to remain between  7.2 and 7.6, ideally at 7.5. The alkalinity levels of the water need to be between 100 and 150ppm. 


  • CTX-15 pH- is a liquid pH reducer used to adjust levels when they are above 7.6. It is one of the best products to avoid and prevent the appearance of lime and the build-up of limescale in your pool. We also have pH enhancers such as CTX-20 pH+.

  • Likewise, we offer total alkalinity regulator products, such as  CTX-21 Alka+, an alkalinity enhancer for when levels are below 125ppm.

  • We also have lime regulator, to ensure this remains at an optimum level of 175ppm. There is also a lime enhancer, CTX-22 Calc+.


Next, the wall of the pool must be brushed to remove any scale that has built up. A brush and surface descaler needs to be used on the surfaces, such as the extra strong descaler CTX-51 WallCleaner Plus, ideal for removing lime, or the CTX-53 WallCleaner Liner, used for those pools which are overrun by limescale. 


Finally, add a drop of CTX-700 Antical Super, once a week to prevent any future limescale build ups.


If you want to resolve the problem of limescale build up as best as possible, speak with us.