It was once said that you can have the most beautifully design award winning pool with top of the range equipment …but if the water is dull, that’s all you will remember. Swimming pool engineers don’t need telling the most important feature of a pool is that the water must be 100% safe and clear at all times. In order to ensure this is the case, satisfactory filtration with correct sanitation, monitored by accurate water testing is absolutely essential. Whilst a typical swimming pool filter unit may produce excellent results on its own, there are times when it could do with a little help by means of flocculation. This is especially the case when a pool may be opened after a winter closure or other times when the pool may have had excessive use, or been contaminated by fine debris causing the water to appear dull or possibly cloudy. Most of us in the Industry are aware that ‘The Standard’ for quality of swimming pool water in the UK is set by the: Pool Water Treatment Advisory Group (PWTAG) and the current standard for turbidity (clarity) published by them is: 0.5 NTU (Nephelometric Turbidity Units). Similar standards exist on a worldwide basis and it is believed that these are based on guidance from the WHO (Word Health Organization).
It is vital that this standard is adhered to at all times to ensure the health safety of the bathers using the pool. Think about it; if pool water becomes so cloudy it could hide dangers within the pool then this could be a serious risk to the bathers. So how should you ensure that the correct clarity is maintained in swimming pool water? In the ‘good old days’ we’d do the coin test; by seeing if we could see the Queen’s head on an old penny thrown in at the deep end, but things have moved on a bit since then. So, let’s start with a simple visual check of the pool water, can you see the bottom clearly in the deepest area? Does the water look dull or cloudy? Beyond that; it is a good policy to test the water turbidity as it is just as important as checking the pH and chemical levels. So it is would be well worthwhile to invest in some reliable and accurate test equipment. Today there are some excellent products available for testing pool water clarity and resolving any problems that may arise. If the water turbidity is outside the standard set by the PWTAG then a suitable flocculent is one of the most practical ways to resolve the problem. But how well does a flocculent work? Last year we carried out some extensive tests, and the results were quite impressive.
During the summer of 2019, I arranged for some flocculent tests to be carried out on two identical test pools. For the tests it was decided to trial a very popular flocculent used for swimming pool filtration, namely MSI’s Jolly Gel which acts in a physical way facilitating the removal of particles by filtration. This product has now been on the market for 28 years and is widely available in the UK the Middle and Far East as well as Europe.
The two test pools that were chosen to be used for the test were at a research centre in Sussex and both were liner pools identical in size and shape, outdoor and open to air. They were also right next to each other so that they would both be subjected to the same conditions particularly air borne pollution. At the start of the exercise, the first test pool No; 004 appeared visually good and the second pool No; 005 appeared visually cloudy. To ensure our test results were absolutely accurate we gratefully received assistance from Tintometer Ltd who loaned us a brand new ‘state of the art’ Turbidity meter. As with most things in life preparation is always key to producing an accurate final result. In this test it was important to measure the pH and chlorine levels at different areas around the test pools, as if they were not properly controlled they could adversely affect the results. We then took turbidity test samples from several areas around the pool, and it became evident that the highest turbidity readings were from the deepest part of the pool, so it was agreed that this would be the best place to take
Those result were then submitted to me for consideration and analysis. The turbidity testing took place over a five day period and the results were quite impressive as you will see from the graph shown. Whilst test pool No 004 started out looking visually good with a turbidity reading of 0.4NTU (being 0.1 NTU below the PWTAG Standard), even so Jolly Gel managed to improve the water clarity by taking the level down to: 0.27NTU which is well below the 0.5NTU standard set by the PWTAG. Perhaps even more impressive was the results for pool No 005, as this pool wasinitially in a very poor condition with a turbidity reading of: 1.28 NTU. After just four days the turbidity level in this pool was reduce to 0.28NTU and although there was a slight rise at the end of 5 days it was still within the 0.5NTU Standard set by the PWTAG. In fact If you take the standard of 0.5 NTU and rate it at 100% then the best results from the two pools was almost 50% better than the set standard.
Mineral Supplies International
Tel. 01825 790524