Rinse out the bowl.
Citric acid wash for pools.
Use a half a pound of vitamin c for every 10 000 gallons of water.
Bosh chemical vanish pool spa stain remover 2lbs natural safe citrus based works excellent on vinyl fiberglass and metals removes rust and other tough stains.
An acid wash would likely remove it you can test by lowering the water level down below the first step and pouring a 50 50 acid water mixture from a flower watering can over the step scrubbing briefly and hosing off within 60 seconds.
For citric acid for pools.
A citric acid wash is most effective on a swimming pool that has been cleaned with all debris removed after it is drained.
Pour water over any remaining.
Pump the mixture into a bowl using a submersible pump.
You will need to use 2 lb.
In your five gallon bucket add one gallon of acid to one gallon of water never the other way around.
Fill the can with 1 gallon of water and then add 1 gallon of citric acid always in that order.
Mix it gently with a mixing stick if you need to.
9 kg of soda.
4 1 out of 5 stars 105.
Dispose of what you pumped as the acid can kill frogs fish and plants.
If you are treating larger stains or decided to buy a liquid acid sprinkle the acid evenly around the pool.
Apply soda ash to the acid puddle scrubbing the mixture with a pool brush.
If it works an acid wash would be a good next step.
The acid wash is applied from a watering can used for flowers.