Should I Put Algaecide In The Pool Before It Rains? (Is It Helpful?)

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Should I Put Algaecide in my Pool Before it Rains?

You see the dark rain clouds moving ominously towards your house. The weatherman has forecast heavy rains for the next few days. Not a good sign. You may be worrying about quite a few things around the house. I am sure the outdoor pool is high on your list. Should I put algaecide in my pool before it rains?

If you are pretty sure of the imminent heavy downpour, Better Put Algaecide In Your Pool Before It Rains. Rain and storms invariably result in an increase in algae spores entering your swimming pool. Prepare your pool before the rains. Algaecide prevents the growth of algae. It will even kill algae to a degree.

Most people are more worried about how they will deal with the outdoor swimming pool after a heavy rain. I totally get it. Leaves, debris, even deck furniture may get blown into the pool. The pool may take in too much water and overflow. Algae bloom may turn your pool green overnight.

Prevention is better than cure, they say. So if you can put in Algaecide and some of the other pool chemicals in the pool before the rains, it might save you a lot of headache and money after the rainstorm.

By the way, you need to take these precautions and preventive measures only if you are expecting heavy rain and storms. A light rain is not going to affect your pool in any significant way.

Does Rain Cause Algae in Pools?

Algae are extremely small living organisms. Algae are not bacteria or from the animal kingdom. Algae are extremely small aquatic plants, capable of photosynthesis. Algae reproduce using spores. Algae spores are in the atmosphere all the time. They move around with the wind currents.

Algae Spores & Nutrients

When it rains, the algae spores in the atmosphere can attach themselves to the raindrops. This is one of the ways algae can enter your pool because of rain. The rain also brings phosphates, nitrates and organic matter with it, which are nutrients for algae.

Debris Blown into the Pool

A rainstorm will also blow leaves and debris into your pool. Algae grows on fallen dry leaves, grass clippings and other yard debris. Algae can even be there on deck furniture which can get blown into the pool during a rainstorm. The debris is also a source of food for the algae to feast and thrive on.

This is another way rain and rainstorms can bring algae into your pool and encourage their growth.

Altered Water Chemistry

Last but not the least is that rain water dilutes your pool. The chemical balance of your pool changes. Alkalinity & pH levels get disrupted. Algaecide and Chlorine levels drop. This will make it a lot easier for algae to grow fast.

So, heavy rain & storms are highly likely to turn your pool green with “algae bloom”.

What to do to your Pool Before it Rains?

Putting Algaecide in your pool before a big rainstorm is an important step in preparing your pool for the rains. But it is not the only thing you can do. Here is a list of some of the things that you can do to prep your pool before the rains.

Reduce Pool Water Level

Rain is going to add water to your pool and raise the water level a few inches. Previous rainfall may have already raised the water level to above the skimmer.

If the water level is higher than the skimmer, then your filter and pump system will not be able to pull in all the leaves and debris floating on the surface.

So it is better to reduce the water level in your pool before it rains again by backwashing your filter. Get the water level to be below the upper edge of the skimmer.

Aim for the water level to be around the middle of the skimmer opening.

If backwashing is not enough to get you there, you can also drain out some more of the pool water by running your pump on the “waste” mode.

Shock Your Pool

Ideally you should be having 3 ppm of free chlorine (FC) in your pool. In reality it may be lower, if you have been busy and missed out on checking the pool water.

Rain will dilute the water chemistry of your pool and chlorine levels will fall further. Rain will also bring in some algae and nutrients to encourage growth. 

In essence, your pool’s defenses will be weak when the algae attack is strong.

Do not let that happen. Shock your pool before it rains. Target for a 5 ppm of free chlorine (FC). Add shock (or liquid chlorine) and algaecide as per the calculation results from https://app.poolcalculator.com/.

Prep your pool before it rains. Chances are you will not be hit by an “algae bloom”.

Clear the Pool Deck

If you are expecting high winds along with the rain, clear your deck  as much as possible. Deck furniture, potted plants, BBQ grills should either be secured or moved to a safe place.

The morning after the storm, you will need to deal with leaves and debris in your pool, anyway. Do not add deck furniture to that list.

Recommended Swimming Pool Chemicals

Best All Purpose Algaecide

Kem-Tek Pool & Spa Concentrated Algaecide is very effective for prevention of algae and also helps to clarify cloudy pool water. It has a non-foaming formula and can be used in all types of pools. Order from Amazon using the link below:

Kem-Tek Pool and Spa 60-Percent Concentrated Algaecide, 1 Quart 2 Pack

Best Multi-purpose Pool Shock

Aqua chem Shock Xtra Blue is suitable for use in all types of pools, including salt water pools, above-ground pools and inground pools. It kills algae, bacteria, and chloramines, effectively and fast. It will make your pool crystal-clear blue and sparkling clean again. Order from Amazon using the link below:

Aqua Chem 5-Pack Shock Xtra Blue for Swimming Pools, 5 Pounds

Bottom Line

The bottom line is that

1. Heavy rains and storms will bring in algae spores and nutrients (that algae breed on), into your pool.
2. Addition of rain water will dilute and alter the water chemistry of your pool.
3. This “double whammy” can result in your swimming pool turning green overnight after a rainstorm due to “algae bloom”.
4. It is better to prep your pool, by adding shock and algaecide, before it rains.
5. You should also get the pool water level down and clear the deck before the rainstorm.

Thank you very much for reading the post. I do hope you found it informative and helpful.