DI resin capacity

[seangee]

Just idle curiosity. In December I treated myself to a 400 gpd flow through upgrade to my old tank based RO system. For the final stage I opted for DI instead of the standard re-mineralising filter they offered. I do not need this and I don't trust them to deliver a consistent level of minerals throughout their lifetime.

For my first few water changes the TDS meter showed 0 as expected. But within a month it was back up to 9ppm which is exactly what I got with the old filter which was RO only. Typically I use around 200l per week for the tanks and a bit extra for drinking, coffee machine, kettle etc. I have now removed the DI cartridge (standard 10x2" but it is a sealed unit) as I really don't need RO/DI. It just seems that this would work out very expensive for someone who did. Yes I know you can buy the resin and re-usable carts as well as replenish the resin. But that's well under 1000 litres of water filtered, and the input was already RO!

OR is it like printer cartridges where the first time freebie is supplied almost empty.

 

[StevenF]

The capacity of a DI cartridge is dependent on the TDS of your water . The higher the TDS and shorter the life. For the bast life of the filter it would be better to. They are useful but the periodic replacement cost ends up being higher than the filter cost for an RO system without the DI filter. i have an ongoing experiment running in a small 5gallon tank (weekly water change0and to prevent changes in the water from impacting the results I have been filtering the water with a DI filter to a TDS of 1. I use a refillable cartridge (Probably larger than your cartridge) and I typically go about 6 yo 8 months on it before it need the media replaced.

One thing I have learned is that RO systems and DI cartridges are not very good at removing boron So IF you don't completely drain the storage bucket before refilling it Boron levels in the storage bucket will increase. I had a TDS-OES lab test done DS of 1 ppm So it appears TDS pens are not very good at detecting boron. The only way I can get my pend to read zero TDS I have to use distilled water which is not practical for me.

 

[seangee]

The capacity of a DI cartridge is dependent on the TDS of your water . The higher the TDS and shorter the life.

That was the reason for my question. What went into to DI cartridge is what came out of the RO system. On average that's a TDS of 9. Tap water is well over 300 which is why I use RO in the first place. (Hard water in the tap + 50ppm nitrates does not go well with my soft water fish). I would have expected it to last ages with almost pure water going in.