When you say cog wheel, do you mean the people dial where you set the hardness or gallons? Describe it because there is nothing on your valve that tells you the capacity but, you are correct that 3/4' is commonly called a 24K. But, that is dependent on what the salt dose is which to get 24K takes 15 lbs. per cuft of resin. Which gets you terrible salt efficiency of only 2000 grains removed per lb of salt.