Always try to take the sample from the point closest to the condenser. Some machines have put a sample port on the condensing tank so this would be a convenient point. Sometimes flood tank 2 would be the closest point where you have a sample port. If you do not have any sample port on the machine, you can get a sample from the water separator. However, because the acid can be in the water layer, and we are trying to test if there is an acid in the solvent, you would need to test both the solvent and water for acid, so it is a good idea to test the pH of the water in the water separator also.