Not normally. Assuming the water pressure is only low on the hot water supply and that its equally low at all faucets, the problem is more likely to be a restriction in the line between the hot water heater and the faucets. Many hot water heaters have two valves at the top--one to shut off the incoming cold water, and one to shut off the out-going hot water (they all should have the cold water valve). If either valve isn't all the way open, the pressure in the line can drop. That's the preferred issue--just turn counterclockwise to open. Built-up mineral deposits in the pipes (if they are steel pipes) is another likely cause--and much more costly to remedy.