Purolite® MB400 premium grade 40% cation and 60% anion mixed bed DI resin is a high-quality, long-life resin which is used after the RO process to further reduce your TDS (total dissolved solids) reading. You should replace the resin when your TDS reading starts to rise.

Purolite® MB400 resin is more suited for aquatic use due to it having a high specification mix of 40% cation and 60% anion components.

The list below shows what elements each of the resins exchange. With most water sources the elements which the anion component exchanges are higher than those exchanged by the cation. This can result in the anion component being exhausted first. When we monitor the water coming from our DI vessels and housings the first element to be detected on a TDS/EC Conductivity meter will be Sodium. This will indicate when the cation part of the resin is exhausted. However with the anion component Silica is the first element to be released when it becomes exhausted, and this cannot be detected on a TDS/EC Conductivity meter.

With Purolite® MB400 resin the cation will always exhaust first due to it being only 40% part of the mix. This avoids the potential risk of an exhausted resin not being detected early enough.