I assume you are buying a complete system and not trying to build it yourself.

Given that, you want to find the correct type and size system for your application (hint - bigger isn't better, you can go too big) rather than focusing on the valve.

One of the big differences between the valves (5600sxt vs 7000) is the flow rate. The 5600 is intended for residential uses, with a continuous flow rate of up to 20 gpm and is for tanks up to 12" in diameter. The 7000 is a high flow valve (up to 28 gpm) and for up to 24" tanks.

You would be fine with a 5600sxt based unit based just on flow rate - but again, you need to size the system first - given your hardness levels and usage.

Right now the big thing that isn't known is the amount of iron.

My water test kit is arriving today, I will provide the details as soon as I have it. Thank you..

Just noticed you said it was city water. That usually doesn't have a lot of iron in it because it's chlorinated. How do you know it's 4.4 grains if you haven't tested it?

Assuming that level of hardness is correct and no iron, here is the math:

4 people x 65 gal per day = 260 gpd

x 4.5 grains per gall = 1170 grains per day

x 7 days =8190 grains per week

x 14 days = 16380 grains per 2 weeks

Typically you want a softener to regen between once a week and no more than every 2 weeks.

Also, you should know that water softener capacity is advertised at 15 - 18 pounds of salt per cu ft of resin - which is an insane amount of salt. So, a softener with 1 cu ft of resin is usually advertised as a 30,000 grain softener.

The salt per cu ft of resin vs capacity isn't linear - in other words, you could cut back to 6 pounds of salt per cubic foot and 1 cubic foot would provide 20,000 grain capacity.

A system with 0.75 cubic ft of resin set at 6 pounds of salt per cubic foot would have a capacity of 15,000 grains and would regen something less than every 2 weeks.

Note that this is a pretty small system - because your water is not very hard at all.

You may be able to find what you need on Amazon.

Thank you Jake for all the information. Getting ready to place an order.