Those who own fibreglass pools often wonder what effect the rain has on their pool water. After a night of heavy rain, what exactly happens to the water in your pool? Does your pool water interact in any way with rain water?
What Happens When It Rains?
Rain is formed when water gets evaporated. It can leave behind minerals, and dissolved solids on the ground, as water is being evaporated into the air. Just prior to when it condenses and turns into rain droplets, this is some of the purest water you can find anywhere on the planet.
When rain is falling through the air, it can pick up pollutants, dust, spores, as well as other contaminants. This can sound similar to how the phosphates in your pool water work.
Should heavy rain be coming to your home, then the rainwater can end up raising the level of water in your pool. When the pool water is high enough, the pool skimmer can cease to function. This means that it will no longer circulate and skim the surface of the pool. As a result, leaves, flower buds, bugs, as well as other debris can accumulate on the surface of your pool. Eventually, these will settle down to the bottom of the pool.
Should rainwater enter the pool, it’s important to backwash the fibreglass pool. If the water level gets too high, you can use a pump to pump the water down.
What Happens To The pH Of The Pool?
The pH of rain is initially neutral. It’s actually a perfect 7.0. However, it starts to absorb contaminants with low pH as it starts to fall through the sky. The effect that low pH rain has on your pool is usually small. This is except when there are heavy rains over a period of a few days. When this happens, you may need to raise the pH of the water in your fibreglass pool.
You could also experience acid rain. Essentially, acid rain is rainwater that has absorbed both sulfuric acid as well as carbonic acid from the gases in the atmosphere. This kind of rain is not always highly acidic, but its pH can be between 5.5-5.6. This is low enough to affect the pH levels of your pool, needing you to raise the pool’s pH.
Will Rain Water Affect Your Pool Alkalinity?
Over time, rain can decrease the total alkalinity level in your Perth fibreglass pool. When this happens, you’ll need to raise the alkalinity of your pool water. Rainwater has a total alkalinity that’s near zero. When there are heavy rains, this will dilute the alkalinity level of the water in your fibreglass pool. It could fall by around 5-10 ppm in a day.
When a pool has low alkalinity as well as low pH levels, then the environment in the water can turn corrosive. This can end up damaging metal surfaces that are inside the water. Pool lights, rails as well as ladders may all be damaged.
Water that is corrosive can damage the pool equipment that the pool water flows through. This includes heaters, filters as well as pumps. To control the corrosive environment, the pH level of the water as well as the total alkalinity of the water will need to be adjusted. You may also need to adjust its calcium hardness.
How Will Heavy Rains Affect Your Pool Calcium Reading?
Rainwater is usually soft water as it has a hardness of near zero. If the water in your pool is too soft to start with, say around 200 ppm. Then, when gallons of rainwater is added to the pool, it can decrease the calcium hardness of the pool. When this happens, you’ll need to increase your fibreglass pool’s calcium hardness.
If the water in the pool is hard to start with, say around 400 ppm calcium hardness, then heavy rain can actually be beneficial for your pool. Actually, allowing rainwater to dilute a pool’s calcium hardness is the only known solution to this problem, by dilution.
Should You Add More Chlorine When It Rains?
By now, you should be able to tell that when there’s rainfall, then the levels of your pool chemistry will be lower. This includes the readings for your pool alkalinity, pH level calcium hardness, chlorine, as well as your pool stabiliser.
Rainfall doesn’t contain chlorine at all. It also brings small amounts of contaminants that will end up in your fibreglass pool. In addition to this, leaves, dirt and debris could also enter your pool. This creates a higher demand for chlorine, and the free chlorine in your pool water is used up.
This is why it’s actually a smart idea to raise the chlorine levels of your pool if you know that heavy rain has been forecasted for your area.
What About Saltwater Pools?
If there are heavy rains then salt pools could get diluted. This is why you’ll need to add more salt to your fibreglass pool. Storms can also bring with them debris from the environment, and this may require more chlorination.
What About Heavy Rains And Algae?
Rainwater doesn’t cause algae by itself, but it can create environments where algae can thrive in. Rain brings with it phosphates, nitrates, as well as other contaminants that are organic, and deposits them in the pool. It can also reduce the chlorine level in the pool.
Should heavy rain be forecasted for your area you’ll need to run your pool through the time it rains, as well as slightly after it. You should also add a dose of algaecide to your pool on a weekly basis. This can help prevent the development of algae. Should your pool turn into a green colour due to the presence of algae, you’ll need to use an algaecide that contains copper in order to get rid of algae from your pool.
Conclusion
Heavy rains can affect the water chemistry of your pool. When this happens, you’ll need to check what your water chemistry levels are and make adjustments as necessary. Use this guide to learn more about what happens to your pool during heavy rains, as well as how you can take care of your pool.