T.D.S and PHOSPHATES
TDS (Total Dissolved Solids)
This is the measure of the total of all soluble substances dissolved in the water. Over time the water can become “saturated” and begin to lose its ability to dissolve solids. When this happens, the only answer is dilution. Either drain off some of the water and top-up or empty the pool and refill.
There are no treatments to keep TDS down; it is a naturally occurring reaction in all bodies of water. It does not happen often in swimming pools as they tend to be topped-up every so often, after a vacuum to waste or natural evaporation etc. thus diluting the water.
Never drain your pool before speaking to the original constructors or your local pool suppliers. Draining a pool can lead to collapse of walls or displacement of the Liner.
If you want your lawn to grow well one of things you would do is feed it with fertiliser which has a specific blend of nitrates and phosphates suitable for your type of grass. In the same way Algae, being a plant, feeds on nitrates and phosphates too.
Phosphates do not cause Algae to grow in your pool but if Algae gets into the water and there is a good balance of phosphates and nitrates then it has a good food source and will grow very quickly overwhelming your sanitiser (Chlorine).
Phosphates, like nitrates, are naturally occurring. They are just about everywhere, in household water, often in rainwater, in lawn care products, decomposing organic matter such as leaves and if you live near a farm they are in the fertilisers sprayed on crops that then go into the ground water.
As of now there is no way to remove nitrates from water, so we concentrate on removing the phosphates and so starve the Algae.
Do remember that it is not a problem that will occur every year. It depends on many factors, the makeup of the water you use, the amount of organic debris that falls into the pool, the nearness to lawns that are sprayed etc.
If you live near farmland and fill your pool from a well it is a good idea to use a phosphate remover on a regular basis in most other cases it may be years before you have a problem.You will need a phosphate remover / killer to reduce the levels and therefore starve any Algae that lands in your pool.