Since the latest version of RODSTAR (126.96.36.199) we have received several questions regarding when to include and when to exclude buoyancy effects. Therefore, I would like to clarify exactly how to use this new option in RODSTAR: For steel rods I recommend always excluding buoyancy effects. If the bottom minimum stress of bottom sucker rod section is in compression, you must add enough sinker bars to make this number positive. For example, if you are using a three tapered rod string with 1", 7/8", and ¾" on the bottom, check the bottom minimum stress on the ¾" rods. If this number is negative, add sinker bars or sinker rods to make this number positive. The bottom of the sinker bar section will always be negative (due to the resistance on the plunger as it moves down on the downstroke). This is normal and is not a problem. For fiberglass & steel rod strings, also do not include buoyancy effects when having RODSTAR design the rod string. However, when you have the final rod string design you want, make one last run by including buoyancy effects and make sure the bottom of the fiberglass rod section is not in compression. If it is, add more steel on the bottom to make sure the fiberglass section is far from being in compression. Please keep in mind that the pump friction number you use in RODSTAR has a large impact on the number of sinker bars you need. The default value in RODSTAR is 200 lbs. However, as discussed in previous newsletters, the actual number may be higher or lower than the default. The way to determine the actual pump friction using a measured dynamometer card is to get a downhole pump card from a wave equation diagnostic program without including buoyancy effects in the calculations. Then, whatever load is below zero on the downhole pump card is the pump friction. However, for this to work, you need to have a load cell that records load very accurately, and you also need to specify the correct amount of rod-tubing friction so the calculated downhole pump card only shows pure fluid load without any left over friction. Another requirement is that the downhole pump card should indicate good pump condition. For example, if the pump card shows pump hitting down, or a severe standing valve leak then you will not be able to accurately determine the pump friction. XDIAG is the only wave equation program that automatically calculates both the correct amount of rod-tubing friction and the pump friction from the downhole pump card.