Our RO system is smaller than a dialysis unit system as we are producing water for an R&D facility. We only produce about 150 liters an hour. I will provide our relative costs; but, hopefully someone in a routine setting has done a cost comparison and can share their information. (although it may all be more of academic than practical interest- see below).

We spend about $60 a month on salt and our RO membranes cost about $35. Maintenance for the softener is about $200 each 3-4 years (we actually do most of our own maintenance so this is a guess at the cost if a service person came to do all the maintenance). As we are an R&D facility and have water which is moderately hard (about 8-12 grains per gallon) there was never any thought about not having a softener.

Home water softener suppliers always say you will save money on soap and detergent if you have a softener. Has anyone ever seen a cost comparison showing the saving exceeds the cost of salt and softener maintenance? I suspect the savings is a lot less than the total cost of the softener. However, everyone prefers soap that lathers easily and dishes that come out spot free.

In dialysis, isn't the goal to produce the best quality water and keep the system down-time at a minimum, by operating the system as efficiently as possible? It would seem that using preventive maintenance (a softener) is preferable to extra system down-time to replace RO membranes. Economics ARE an issue. However, even if a softener costs a bit more than an extra set of membranes, it seems using a softener fits better into the philosophy of preventing the problem before it occurs.

Certainly a softener is not necessary in all settings. Some dialysis units do not test the hardness of their water supply and do not have a softener as the hardness level of their water is quite low. Deciding whether to put in a softener is a matter of weighing the pros and cons with your water system supplier and your administration.