Whittier Plumber, La Habra Plumber

When the hot side pressure is bad in all of the house it is going to be a problem with the hot water heater outlet usually. If it is just bad at one location especially when it is the shower and your shower is a single handle unit, it is the cartridge in the valve body. It is a very common problem with Moen valves as well. Simply replace cartridge by removing trim then cartridge and install new one. They should carry your part at home depot. You will be back in business.

If it is all over the house try replacing the hot side nipple and supply line coming out of heater,that will usually take care of it. If not it could be build up in piping and you might need a repipe.