Stick with a 0.2, 0.5 or no larger than 1.0 micron sediment filter, a 0.5 or 1.0 micron carbon block, the current RO membrane and MaxCap DI but use any high quality mixed bed DI resin in the final cartridge. The MaxCap DI will still protect the mixed bed and make it last at least 3x longer than it would otherwise.
Why are you using such a coarse carbon block? The lifespan and chlorine removal capacity of a 5 micron is not near what a 1 or 0.5 micron version are. The whole idea is a RO/DI should be a well thought out systems from start to finish. Each piece plays an important role in protecting whatever is downstream of it and making the entire system function better, last longer and ultimately cost less to own and operate over its useful life.
Do you make that much water that you need bulk resin? I use the MaxCap UHE in Phoenix with a tap TDS over 500 and my SilicaBuster cartridges last about 3 years with each MaxCap replacement about 1 year and we do have some CO2 in our water here which shortens DI life. What are your tap, RO only and MaxCap DI TDS readings? What is your exact measured waste ratio, your water pressure at the membrane and your water temperature? Have you measured the CO2 content of your water to see if this may be part of the problem? Have you spoken to Spectrapure to see if they can offer any advice? They are very helpful to all the reefers around AZ and even sponsor clubs and events and do speaking engagements to teach about water quality. I have seen them go as far as rebuilding someones system to see what they could do to improve it.
