Any hot tub owner knows that maintaining it well can be a complex business of testing and balancing and you can sometimes wish that you had paid more attention in chemistry lessons at school. While you don’t have to be a science geek to own a hot tub, it can really help to have an insight into why you use the processes necessary and how they keep the water, and the unit itself, clean and safe.
One of the issues you may encounter is your water turning green, so why does it do that? How can you treat it? And how can you prevent it from happening in the first place? Keep reading – all the answers you need are below.
Why has your water turned green?
Green hot tub water is neither inviting nor safe to use so there really is no way of getting around it – you need to sort it ASAP. There are 2 main reasons why this might have happened:
Green algae
If you have a green hot tub, it’s highly likely that you have green algae living in it. Algae can proliferate rapidly, and this is why water can transform from crystal clear to swampy green in just a few days. Now, you might be thinking; isn’t my chlorine supposed to stop this? And yes, it’s true that green algae can only take over your hot tub if your chlorine (or bromine) isn’t working properly. However, just dosing your water up with chemicals isn’t always the answer.
Unbalanced Water is Unhealthy Water
The most common cause of algae is simply that the water chemistry is off. Algae spores are so common that you can’t really avoid them ending up in your tub, but as long as the water is healthy they won’t be able to gain a foothold and take over. If your water has too few or too many chemicals in it, or if the pH or total alkalinity is a little off, this can lead to that unpleasant green slime spreading throughout your hot tub as it'll limit the effectiveness of your chlorine. Try to test your water so you can identify what might be the cause of the algae growth – this could save you a lot of time later on.
Minerals and contaminants
The introduction of a range of contaminants can affect water. Some of the most common contaminants are the minerals from the oxidisation of metals such as copper and iron. They can be worn away from copper pipes, corrosion of equipment, or even just minerals from the water itself.
Contaminants that you introduce to the water yourself can also be an issue, such as bodily substances (eg sweat), cosmetics, fake tan, body lotions, and perfumes.
Pollen can also turn the water green in outdoor hot tubs. Because pollen grains are very small and lightweight, they can be easily carried on breezes and end up in the hot tub. Because they are so tiny, filters can struggle to remove them and so they remain in the water, discolouring it.
Getting rid of green water in a hot tub
You have two options here: treat the water to make it clear once more or drain the water and start again. Generally, if your hot tub is overgrown with algae, it’s advisable to drain the water and try again. However, this isn’t always necessary. It’s important to have a good understanding of the cause of the greening so that you can treat it accordingly. Use the following guide to determine the issue and apply the right treatment:
Algae: if the water smells off, looks cloudy, and feels slimy to the touch then this indicates the issue is algae. To treat this, you will need to use an algaecide or a shock treatment of fast-dissolving chlorine. You can increase the efficacy of algaecide by brushing the surfaces of the hot tub to help break up algal blooms. Make sure your tub’s pumps are running to ensure the chemicals circulate effectively.
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Metal oxidisation: if the water is green but still clear it could be copper or iron minerals. Adding a sequestering or chelating agent will group any metal ions together which can then be filtered out of the water. Make sure you clean your filters after this using your filter cleaner.
Pollen: this will often settle at the bottom of the hot tub so if it looks greener and murkier at the base of the shell or becomes cloudier if you agitate the water, it could be pollen. In the same way that a sequestering agent will group metal ions together, a spa clarifier will cause small particles to clump and therefore filtered. Again, clean or replace the filter afterwards.
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If you’re really not sure what the cause is, the water is looking particularly contaminated, or it’s been green for more than a few days, it’s best to drain the affected water away and start afresh. Once empty, give it a thorough clean, including the filters (an overnight chemical soak is a good idea if you’re not changing them). Take a good look at any metal components for any signs of rust or corrosion as this could be the cause of the greening. Then refill and balance as you would usually do.
Prevention is Better Than the Cure
Prevention is always better than the cure when it comes to algae. There are things you can do to avoid unpleasant green water problems. Firstly, being very vigilant in achieving the right levels of sanitiser will help prevent algae from gaining a foothold in the first place. In addition to this, smaller doses of algaecide can be applied periodically to keep any potential formations at bay.
You should also keep a close eye on your total alkalinity (TA). TA that is too high can reduce the efficiency of your sanitiser. Too low and it can corrode metal which can lead to copper or iron oxidisation. It also acts as a buffer, that helps keep your pH levels nice and stable.
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Try to minimise the contaminants that can be introduced into the hot tub by showering before using. This will help wash away any potential algae spores or other contaminants before you get into the tub. You should also keep the cover on when you're not using your hot tub to prevent pollen and external debris from getting in.
