The resin in this filter system is designed for a pH range of 5 to 9, meaning it should work even at a pH of 6, where the water is slightly acidic.
However, you should note that although the resin can work in this pH range, slightly acidic water (pH 6) is not ideal for use as drinking water. In the long term, acidic water can cause corrosion in pipes and affect the taste of the water.
If you plan to use the filtered water as drinking water, it is recommended to also install a deacidification system. Such a system can increase the pH of the water and make it more neutral, which is not only beneficial for iron filtration but also improves the quality of drinking water and protects your plumbing.