This simple fix will eliminate pool stains
There is a better way to prevent pool stains – one that does not require purchasing any particular product. It only involves a slight adjustment on how you balance your pool – Jock Hamilton
When we are asked to diagnose the reason a pool developed a stain, our first question is always “what’s the alkalinity level?” Okay, it’s not technically the FIRST question, but it’s often the most important one. This is because a pool’s Total Alkalinity (TA) has a direct relationship to stains. Without getting too chemically nerdy, TA measures carbonates – when carbonates and metals/calcium react – you get staining/scale.
However, carbonates are not all bad; they help stabilize your pH and when they are too low they can make the water become more corrosive in a plaster pool. The secret is moderation – just enough to get all those benefits – but low enough to avoid stains. This is the concept behind our Hamilton Index that we use to balance pools. The idea is simple: test Total Hardness to indicate if you have issues in your water that can stain, then balance your Alkalinity accordingly.
TIP: Lower your Total Alkalinity
Lower your TA. If your pool seems to stain pretty often, it is because metals are getting into the water – from rain, source water, debris, etc. This is not something you can really prevent, but you can balance based on it. Start with where you normally balance your TA based on whatever index you happen to use, and drop your TA 10 ppm. Then see what the pool does. If the stains never come back, keep TA there. If they do, but take a bit longer to return, drop another 10PPM and observe.
The rule of thumb is- the harder your water is, the lower the TA needs to be. For relative normal water of around 350 Total Hardness (approx. 250 Calcium Hardness), you should keep the TA below 90-100 ppm; higher than this you’re likely to stain. At an extreme of 2000 Hardness, you would need to maintain below 40 ppm TA.
The great thing about the 10 ppm at a time trick is that you can tailor your balancing to your pool. While test kits having become more accurate over the years, there is always some testing error. But by doing based on the behavior of the pool – which is what you really care about – you can prevent stains and scale, never needing to buy a product.