I can find Delta calculations on the web. Can anyone tell me how you accurately size circ. pumps and CV ratings for zone valves? I assume you need to know the head pressure and GPM's. How does one figure that out? How do you know how many GPM's fit a particular application? I think my taco 007 is too small for charging my storage tank. Even though I can get the tank to 175* in a reasonable time, I can not get the temps much higher then that in the tank. I have not tried burning more then one load at a time ( about 6 hours because comb. air damper is open full time). But the tank hits 175* before the load is done. Also the CV rating on my zone valves are low (about 4). I can get zone valves with a CV rating of 7 but I want to make sure that is a high enough rating.