How To Fix A Green Pool
Here are our tips and step-by-step guide on how to fix a green pool. With good measurements and the right chemical volumes we can reliably “dose” a pool and walk away with confidence that it will come good. The only intervention is a bit of back washing to clear the flocculant from the filter, read on.
NEVER MIX CHEMICALS OUTSIDE THE POOL
How To Fix a Green Pool
1. Check cynauric acid
Commonly known as a stabiliser, cyanuric acid is persistent in pool water. It’s only diluted by water changes (draining and topping up). Too much cynauric acid locks up the chlorine, stopping it from killing the algae and turning the pool green. If it’s over 100 ppm, drain half the water from the pool to get rid of it, and then refill before you try to kill the algae.
2. Set the pump running
We’ll need to move the water continuously for the next 24 hours or so. This is to mix the chemicals we’ll be adding and to remove the dead algae via the filter.
3. Correct the pH
The wrong pH rapidly reduces the effectiveness of chlorine. You need to adjust the pH to 7.2 to deal with a green pool. Use a test kit to measure the pH and follow the instructions for the volume of water in your pool, to make the adjustment. Add acid carefully, spreading it around the pool, to lower the pH. If the pool has a pH lower than 7.2, you can generally leave it till after the end of this process and then add alkali to increase the pH to bring it within the optimum range of 7.2 to 7.6.
4. Add chlorine to fix the green pool
We give the pool a big dose of chlorine (super-chlorination is the industry term). This kills the algae that are making the pool green. The amount required depends on the degree of the problem but it is not unusual to add between 5 and 15 liters (one of those blue drums) of chlorine for the average 50,000 liter pool.
With a good dose of chlorine and corrected pH the algae will be killed, being bleached in the process. This leaves less green but cloudier water from all the dead bleached algae. To remove them we use a flocculant that makes them clump together so that the filter can remove them from the water.
The dead algae now trapped in the filter needs to be removed to keep it working efficiently. You need to periodically backwash the filter (say 2-3 times per 24 hours depending on how much algae there is) to send it to waste.
7. Slow release flocculant
A really green pool contains a large amount of algae. We need to get rid of all of it. To help with the task add a slow release flocculant tablet to the skimmer box.
8. Phosphate level test
Lastly we test the phosphate levels in the water. Phosphate is a fertiliser that will promote the growth of algae. It can enter the water from garden run off and bird droppings. If the levels are too high it could be contributing to the algae problem. To treat we use a phosphate remover (commonly called starver).
DO NOT RE-ENTER THE WATER TILL THE CHLORINE LEVEL HAS DROPPED BACK TO NORMAL USUALLY <3 PPM
Does fixing a green pool sound complicated?
It is – keep in mind this is a general guide only. If a pool is going green on a recurring basis there’s likely to be a root cause that warrants investigation.
Let’s face it, even once you know how to fix your green swimming pool there are better things to do with your weekend and things to spend money on than pool chemicals.
Sign up for the Pooled Energy system and;
a) your pool won’t go green in the first place
b) in the extremely improbable event that it did (never say never), our monitoring would alert us and we’d send someone to fix it – free of charge.