Dear  K.M.Senthil kumar ," ...

Dear  K.M.Senthil kumar ,

" Remember that all good iron filters should have water of at least 7.5 pH or higher to work properly. Some, such Filters, often need a pH of at least 8.0. ALL oxidizing filters need at least a pH of 7.5 or higher. The pH of 7 or below the iron removal unit will not be work properly and adverse effect. There is almost always serious drawbacks with lower pH water when using iron filters.

1. The sequence of the treatment is ok. The inlet pH is 7 then why treatment required ?, you can bypass some step like iron removal, I think this is the problem of iron removal unit, because the This  Iron Removal Filter  Cartridge contains the same media (Permanganate Treated Zeolite) employed in many expensive iron water filtration systems, When the dissolved iron comes in contact with the manganese greensand media, it is rapidly oxidized, turning the ferrous iron into a ferric form which is then mechanically filtered and removed from the water. When the iron water filter has reached the end of its service life, it is simply replaced with a new cartridge - there is no media to regenerate, no backwashing, your iron removal system is not working and my suggestion some time you pass this unit then analyse the PH.
2. Check the line corrosion.
3. Pump & pump line material.
4. If heavy metal present then reflect the inlet pH.
5. So there is no outside problem it is the problem of within system

Regards

Prem Baboo