How do I treat a green pool?

There are two common methods to treat green pools; chemically and using floc. Please ensure that if you are doing this, you have all the correct PPE gear and read the instructions on your chemical bottles carefully.

The Floc Treatment

We suggest using floc only if there is no big debris in the pool. If you have larges leaves, sticks and branches, forget it. It will stir everything up when you’re trying to vacuum and cause more headaches than it’s worth. If it’s just algae on the walls and floor, flocculent is the perfect way to clean it up.

Before proceeding there are a few things you will need to check. Firstly, do you have a waste line. Secondly, what filter do you have?

What filter do you have?

Once you have decided to floc the pool, please do a water test. Flocculants will have instructions on the side, it’s very important to follow these. They require you to adjust the pH of the water before adding it. If you have a cartridge filter, remove it and put the lid back on. If you have a media filter, put the handle on recirculate. If chlorine is low, add some liquid and brush every surface you can. Fill the pool to the highest point you can. Let the pump run for a couple of hours, then turn everything off and let it sit for a few days.

If done properly, the flocculent will drop everything to the floor and leave you with crystal clear water and puffy/cloudy mess at the bottom. Now gently vacuum this to waste and you’ll be left with a clean pool.

If you don’t get everything, fill the pool back up and go again the following day. If it’s just a tiny amount left, just stir it up by brushing. Put your cartridge back, or move the handle to filter, and balance the pool.

Chemically Treating

Treating a pool chemically is the most common way we treat green pools. To do this simply:

  1. Grab your PPE gear (glasses and gloves in particular).

  2. Turn on the pump.

  3. Add both granular and liquid chlorine. I add the granular chlorine slowly to the skimmer basket, but you are welcome to add it to a bucket and dissolve before spreading through the pool.

  4. Pour the liquid directly into the pool.

    I find algaecide and clarifier somewhat useful, but not essential to the treatment. Others may disagree and that’s completely fine.

How much chlorine do I add?

Well, this is the million-dollar question.

  • How green is your pool?

  • How big is it?

  • What time of the year is it?

Assuming you have a 40,000L in ground pool that has been green for no more than about 3 months,

I suggest 15L of liquid, and 1 to 2 kilos of granular chlorine.

  1. Fill the pool so the water level is much higher than you would normally run it (we suggest as high as you can without it overflowing).

  2. Brush the walls and floor to dislodge the algae, scoop the pool and remove as much debris as possible, and take the blanket off for the entire process of the treatment.

  3. Run the pump for as many hours as you can (24 hours a day if possible, but at least daylight hours).

  4. Check the colour and chlorine level again every day at the same time if possible.

    If you’re back close to zero for chlorine, and the pool hasn’t changed colour, add the same amount again (you may be required to add some acid as well, so keep it on hand).

  5. Repeat until you see a change in colour, or your chlorine levels remain high.
    You will need to backwash, or clean your filter often, but make sure you do it prior to adding chemicals or you are simply washing away all the good work.
    It is important to try and remove as much debris as possible through this process, but to do this you will be stirring up the water.
    Do this early and often - then try and let it sit once you’ve got the majority of it out.

  6. Once the water goes crystal clear, the algae will all be grey or whitish and on the bottom of the bottom of the pool. This needs to be removed. The best way to do this is to vacuum it to waste.

  7. Fill the pool to the very top, turn the handle to waste (on a media filter it’s marked, on a cartridge filter you will need to turn a 3 way valve and connect a hose), and vacuum it gently. You may be required to stop and empty baskets, and you may have to stop and fill the pool again.

  8. Once all is removed, top the water up to the correct level and balance your pool.

It is crucial you understand why your pool went green in the first place, so if unsure, try and engage an expert to help with that.